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Sample records for caulobacter crescentus s-layer

  1. Transcriptional regulation of the S-layer protein type I secretion system in Caulobacter crescentus.

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    Toporowski, Michael C; Nomellini, John F; Awram, Peter; Levi, Assaf; Smit, John

    2005-10-01

    The Gram-negative Caulobacter crescentus exports RsaA, the crystalline S-layer subunit protein using a dedicated type I secretion system. The protein and two transporter genes (rsaADE) are located together, comparable to the Escherichia coli type I hemolysin hlyCABD operon, where read through of a stem loop following hlyCA results in reduced transcription of the hlyBD. Using two genetic approaches and a direct assessment of transcription from regions 5' to the genes we learned that rsaD and rsaE were transcribed together as a separate transcript from rsaA. These results are contrary to previous assumptions about the rsaADE type I secretion gene control and add another theme to the area of type I secretion transcription regulation. It may be that to accommodate the high levels of RsaA secretion, the type I transporters must be transcribed independently from rsaA.

  2. Two Outer Membrane Proteins Contribute to Caulobacter crescentus Cellular Fitness by Preventing Intracellular S-Layer Protein Accumulation

    Energy Technology Data Exchange (ETDEWEB)

    Overton, K. Wesley; Park, Dan M.; Yung, Mimi C.; Dohnalkova, Alice; Smit, John; Jiao, Yongqin

    2016-09-23

    ABSTRACT

    Surface layers, or S-layers, are two-dimensional protein arrays that form the outermost layer of many bacteria and archaea. They serve several functions, including physical protection of the cell from environmental threats. The high abundance of S-layer proteins necessitates a highly efficient export mechanism to transport the S-layer protein from the cytoplasm to the cell exterior.Caulobacter crescentusis unique in that it has two homologous, seemingly redundant outer membrane proteins, RsaFaand RsaFb, which together with other components form a type I protein translocation pathway for S-layer export. These proteins have homology toEscherichia coliTolC, the outer membrane channel of multidrug efflux pumps. Here we provide evidence that, unlike TolC, RsaFaand RsaFbare not involved in either the maintenance of membrane stability or the active export of antimicrobial compounds. Rather, RsaFaand RsaFbare required to prevent intracellular accumulation and aggregation of the S-layer protein RsaA; deletion of RsaFaand RsaFbled to a general growth defect and lowered cellular fitness. Using Western blotting, transmission electron microscopy, and transcriptome sequencing (RNA-seq), we show that loss of both RsaFaand RsaFbled to accumulation of insoluble RsaA in the cytoplasm, which in turn caused upregulation of a number of genes involved in protein misfolding and degradation pathways. These findings provide new insight into the requirement for RsaFaand RsaFbin cellular fitness and tolerance to antimicrobial agents and further our understanding of the S-layer export mechanism on both the transcriptional and translational levels in

  3. Two outer membrane proteins are required for maximal type I secretion of the Caulobacter crescentus S-layer protein.

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    Toporowski, Michael C; Nomellini, John F; Awram, Peter; Smit, John

    2004-12-01

    Transport of RsaA, the crystalline S-layer subunit protein of Caulobacter crescentus, is mediated by a type I secretion mechanism. Two proteins have been identified that play the role of the outer membrane protein (OMP) component in the RsaA secretion machinery. The genes rsaF(a) and rsaF(b) were identified by similarity to the Escherichia coli hemolysin secretion OMP TolC by using the C. crescentus genome sequence. The rsaF(a) gene is located several kilobases downstream of the other transporter genes, while rsaF(b) is completely unlinked. An rsaF(a) knockout had approximately 56% secretion compared to wild-type levels, while the rsaF(b) knockout reduced secretion levels to approximately 79%. When expression of both proteins was eliminated, there was no RsaA secretion, but a residual level of approximately 9% remained inside the cell, suggesting posttranslational autoregulation. Complementation with either of the individual rsaF genes by use of a multicopy vector, which resulted in 8- to 10-fold overexpression of the proteins, did not restore RsaA secretion to wild-type levels, indicating that both rsaF genes were required for full-level secretion. However, overexpression of rsaF(a) (with normal rsaF(b) levels) in concert with overexpression of rsaA resulted in a 28% increase in RsaA secretion, indicating a potential for significantly increasing expression levels of an already highly expressing type I secretion system. This is the only known example of type I secretion requiring two OMPs to assemble a fully functional system.

  4. Immobilization of bacterial S-layer proteins from Caulobacter crescentus on iron oxide-based nanocomposite: synthesis and spectroscopic characterization of zincite-coated Fe₂O₃ nanoparticles.

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    Habibi, Neda

    2014-05-05

    Zinc oxide was coated on Fe2O3 nanoparticles using sol-gel spin-coating. Caulobacter crescentus have a crystalline surface layer (S-layer), which consist of one protein or glycoprotein species. The immobilization of bacterial S-layers obtained from C. crescentus on zincite-coated nanoparticles of iron oxide was investigated. The SDS PAGE results of S-layers isolated from C. crescentus showed the weight of 50 KDa. Nanoparticles of the Fe2O3 and zinc oxide were synthesized by a sol-gel technique. Fe2O3 nanoparticles with an average size of 50 nm were successfully prepared by the proper deposition of zinc oxide onto iron oxide nanoparticles surface annealed at 450 °C. The samples were characterized by field-emission scanning electron microscope (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR). Copyright © 2014 Elsevier B.V. All rights reserved.

  5. Screen for localized proteins in Caulobacter crescentus.

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    Jay H Russell

    2008-03-01

    Full Text Available Precise localization of individual proteins is required for processes such as motility, chemotaxis, cell-cycle progression, and cell division in bacteria, but the number of proteins that are localized in bacterial species is not known. A screen based on transposon mutagenesis and fluorescence activated cell sorting was devised to identify large numbers of localized proteins, and employed in Caulobacter crescentus. From a sample of the clones isolated in the screen, eleven proteins with no previously characterized localization in C. crescentus were identified, including six hypothetical proteins. The localized hypothetical proteins included one protein that was localized in a helix-like structure, and two proteins for which the localization changed as a function of the cell cycle, suggesting that complex three-dimensional patterns and cell cycle-dependent localization are likely to be common in bacteria. Other mutants produced localized fusion proteins even though the transposon has inserted near the 5' end of a gene, demonstrating that short peptides can contain sufficient information to localize bacterial proteins. The screen described here could be used in most bacterial species.

  6. The core and O-polysaccharide structure of the Caulobacter crescentus lipopolysaccharide.

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    Jones, Michael D; Vinogradov, Evgeny; Nomellini, John F; Smit, John

    2015-01-30

    Here we describe the analysis of the structure of the lipopolysaccharide (LPS) from Caulobacter crescentus strain JS1025, a derivative of C. crescentus CB15 NA1000 with an engineered amber mutation in rsaA, leading to the loss of the protein S-layer and gene CCNA_00471 encoding a putative GDP-L-fucose synthase. LPS was isolated using an aqueous membrane disruption method. Polysaccharide and core oligosaccharide were produced by mild acid hydrolysis and analyzed by nuclear magnetic resonance spectroscopy and chemical methods. Spectra revealed the presence of two polysaccharides, one of them, a rhamnan, could be removed using periodate oxidation. Another polymer, built from 4-amino-4-deoxy-D-rhamnose (perosamine), mannose, and 3-O-methyl-glucose, should be the O-chain of the LPS according to genetic data. The attribution of the rhamnan as a part of LPS or a separate polymer was not possible. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. The coding and noncoding architecture of the Caulobacter crescentus genome.

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    Jared M Schrader

    2014-07-01

    Full Text Available Caulobacter crescentus undergoes an asymmetric cell division controlled by a genetic circuit that cycles in space and time. We provide a universal strategy for defining the coding potential of bacterial genomes by applying ribosome profiling, RNA-seq, global 5'-RACE, and liquid chromatography coupled with tandem mass spectrometry (LC-MS data to the 4-megabase C. crescentus genome. We mapped transcript units at single base-pair resolution using RNA-seq together with global 5'-RACE. Additionally, using ribosome profiling and LC-MS, we mapped translation start sites and coding regions with near complete coverage. We found most start codons lacked corresponding Shine-Dalgarno sites although ribosomes were observed to pause at internal Shine-Dalgarno sites within the coding DNA sequence (CDS. These data suggest a more prevalent use of the Shine-Dalgarno sequence for ribosome pausing rather than translation initiation in C. crescentus. Overall 19% of the transcribed and translated genomic elements were newly identified or significantly improved by this approach, providing a valuable genomic resource to elucidate the complete C. crescentus genetic circuitry that controls asymmetric cell division.

  8. Analysis of the terminus region of the Caulobacter crescentus chromosome and identification of the dif site

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    Jensen, Rasmus Bugge

    2006-01-01

    The terminus region of the Caulobacter crescentus chromosome and the dif chromosome dimer resolution site were characterized. The Caulobacter genome contains skewed sequences that abruptly switch strands at dif and may have roles in chromosome maintenance and segregation. Absence of dif or the Xer...

  9. Intergenerational continuity of cell shape dynamics in Caulobacter crescentus

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    Wright, Charles S.; Banerjee, Shiladitya; Iyer-Biswas, Srividya; Crosson, Sean; Dinner, Aaron R.; Scherer, Norbert F.

    2015-03-01

    We investigate the intergenerational shape dynamics of single Caulobacter crescentus cells using a novel combination of imaging techniques and theoretical modeling. We determine the dynamics of cell pole-to-pole lengths, cross-sectional widths, and medial curvatures from high accuracy measurements of cell contours. Moreover, these shape parameters are determined for over 250 cells across approximately 10000 total generations, which affords high statistical precision. Our data and model show that constriction is initiated early in the cell cycle and that its dynamics are controlled by the time scale of exponential longitudinal growth. Based on our extensive and detailed growth and contour data, we develop a minimal mechanical model that quantitatively accounts for the cell shape dynamics and suggests that the asymmetric location of the division plane reflects the distinct mechanical properties of the stalked and swarmer poles. Furthermore, we find that the asymmetry in the division plane location is inherited from the previous generation. We interpret these results in terms of the current molecular understanding of shape, growth, and division of C. crescentus.

  10. Evaluation of a new system for developing particulate enzymes based on the surface (S)-layer protein (RsaA) of Caulobacter crescentus: fusion with the beta-1,4-glycanase (Cex) from the cellulolytic bacterium Cellulomonas fimi yields a robust, catalytically active product.

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    Duncan, Gillian; Tarling, Chris A; Bingle, Wade H; Nomellini, John F; Yamage, Mat; Dorocicz, Irene R; Withers, Stephen G; Smit, John

    2005-11-01

    Immobilized biocatalysts, including particulate enzymes, represent an attractive tool for research and industrial applications because they combine the specificity of native enzymes with the advantage that they can be readily separated from end product and reused. We demonstrated the use of the Caulobacter crescentus surface (S)-layer protein (RsaA) secretion apparatus for the generation of particulate enzymes. Specifically, a candidate protein made previously by fusion of the beta-1,4-glycanase (Cex) from the cellulolytic bacterium Cellulomonas fimi with the C-terminus of RsaA was evaluated. Cex/RsaA cleaved the glycosidic linkage in the artificial substrate p-nitrophenyl-beta-D-cellobioside with a KM similar to that of native Cex (1.1 mM for Cex/RsaA vs 0.60 mM for Cex), indicating that the particulate Cex enzyme was able to bind substrate with wild-type affinity. By contrast, the kcat value was significantly reduced (0.08 s-1 for Cex/RsaA vs 15.8 s-1 for Cex), likely owing to the fact that the RsaA C-terminus induces spontaneous unstructured aggregation of the recombinant protein. Here, we demonstrated that not only can an RsaA fusion protein be cheaply produced and purified to a high yield (76 mg/L of dry wt for Cex/RsaA), but it can also be efficiently recycled. The Caulobacter S-layer secretion system therefore offers an attractive new model system for the production of particulate biocatalysts.

  11. Genomic Diversity of Type B3 Bacteriophages of Caulobacter crescentus.

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    Ash, Kurt T; Drake, Kristina M; Gibbs, Whitney S; Ely, Bert

    2017-07-01

    The genomes of the type B3 bacteriophages that infect Caulobacter crescentus are among the largest phage genomes thus far deposited into GenBank with sizes over 200 kb. In this study, we introduce six new bacteriophage genomes which were obtained from phage collected from various water systems in the southeastern United States and from tropical locations across the globe. A comparative analysis of the 12 available genomes revealed a "core genome" which accounts for roughly 1/3 of these bacteriophage genomes and is predominately localized to the head, tail, and lysis gene regions. Despite being isolated from geographically distinct locations, the genomes of these bacteriophages are highly conserved in both genome sequence and gene order. We also identified the insertions, deletions, translocations, and horizontal gene transfer events which are responsible for the genomic diversity of this group of bacteriophages and demonstrated that these changes are not consistent with the idea that modular reassortment of genomes occurs in this group of bacteriophages.

  12. Correction of the Caulobacter crescentus NA1000 genome annotation.

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    Bert Ely

    Full Text Available Bacterial genome annotations are accumulating rapidly in the GenBank database and the use of automated annotation technologies to create these annotations has become the norm. However, these automated methods commonly result in a small, but significant percentage of genome annotation errors. To improve accuracy and reliability, we analyzed the Caulobacter crescentus NA1000 genome utilizing computer programs Artemis and MICheck to manually examine the third codon position GC content, alignment to a third codon position GC frame plot peak, and matches in the GenBank database. We identified 11 new genes, modified the start site of 113 genes, and changed the reading frame of 38 genes that had been incorrectly annotated. Furthermore, our manual method of identifying protein-coding genes allowed us to remove 112 non-coding regions that had been designated as coding regions. The improved NA1000 genome annotation resulted in a reduction in the use of rare codons since noncoding regions with atypical codon usage were removed from the annotation and 49 new coding regions were added to the annotation. Thus, a more accurate codon usage table was generated as well. These results demonstrate that a comparison of the location of peaks third codon position GC content to the location of protein coding regions could be used to verify the annotation of any genome that has a GC content that is greater than 60%.

  13. Whole-genome transcriptional analysis of heavy metal stresses inCaulobacter crescentus

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    Hu, Ping; Brodie, Eoin L.; Suzuki, Yohey; McAdams, Harley H.; Andersen, Gary L.

    2005-09-21

    The bacterium Caulobacter crescentus and related stalkbacterial species are known for their distinctive ability to live in lownutrient environments, a characteristic of most heavy metal contaminatedsites. Caulobacter crescentus is a model organism for studying cell cycleregulation with well developed genetics. We have identified the pathwaysresponding to heavy metal toxicity in C. crescentus to provide insightsfor possible application of Caulobacter to environmental restoration. Weexposed C. crescentus cells to four heavy metals (chromium, cadmium,selenium and uranium) and analyzed genome wide transcriptional activitiespost exposure using a Affymetrix GeneChip microarray. C. crescentusshowed surprisingly high tolerance to uranium, a possible mechanism forwhich may be formation of extracellular calcium-uranium-phosphateprecipitates. The principal response to these metals was protectionagainst oxidative stress (up-regulation of manganese-dependent superoxidedismutase, sodA). Glutathione S-transferase, thioredoxin, glutaredoxinsand DNA repair enzymes responded most strongly to cadmium and chromate.The cadmium and chromium stress response also focused on reducing theintracellular metal concentration, with multiple efflux pumps employed toremove cadmium while a sulfate transporter was down-regulated to reducenon-specific uptake of chromium. Membrane proteins were also up-regulatedin response to most of the metals tested. A two-component signaltransduction system involved in the uranium response was identified.Several differentially regulated transcripts from regions previously notknown to encode proteins were identified, demonstrating the advantage ofevaluating the transcriptome using whole genome microarrays.

  14. Proteome of Caulobacter crescentus cell cycle publicty accessible on SWICZ server

    Czech Academy of Sciences Publication Activity Database

    Vohradský, Jiří; Janda, Ivan; Grunenfelder, B.; Berndt, P.; Roder, D.; Langen, H.; Weiser, Jaroslav; Jenal, U.

    2003-01-01

    Roč. 3, - (2003), s. 1874-7882 ISSN 1615-9853 R&D Projects: GA ČR GA310/03/0293; GA AV ČR IAA5020211 Grant - others:GA Swiss National Science Foundation fellowship(XX) 31-59050.99 Institutional research plan: CEZ:AV0Z5020903 Keywords : bioinformatics * caulobacter * crescentus Subject RIV: EE - Microbiology, Virology Impact factor: 5.766, year: 2003

  15. Reduction of Cr(VI) and survival in Cr-contaminated sites by Caulobacter crescentus

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    Hu, P.; Chakraborty, R.; Brodie, E. L.; Andersen, G. L.; Hazen, T. C.

    2008-12-01

    The Caulobacter spp. is known to be able to live in low-nutrient environments, a characteristic of most heavy metal-contaminated sites. Recent studies have shown that Caulobacter crescentus can grow in chemically defined medium containing up to 1 mM uranium. Whole-genome transcriptional analysis and electron microscopic imaging of heavy metal stresses in Caulobacter crescentus also provided insight and evidence that the bacterium used an array of defensive mechanisms to deal with heavy metal stresses. In addition to up-regulated enzymes protecting against oxidative stress, DNA repair and down-regulated potential chromium transport, one of the major gene groups respond to chromium stress is "electron transport process and cytochrome oxidases", including cytochrome c oxidases, raising the possibility that the cells can employ the cytochromes to reduce chromium. Analysis of the microbial community at the chromium contaminated DOE site at Hanford, WA revealed the presence of Caulobacter spp. As an oligotroph, Caulobacter can play a significant role in chromium reduction in the environment where the nutrients are limited. This result was confirmed by both 16S rDNA based microarray (Phylochip) as well as by MDA-based clone library data. Based on these results we further investigated the capability of this organism to reduce Cr(VI) using the well known model strain Caulobacter crescentus CB15N. Preliminary cell suspension experiments were set up with glucose as the electron donor and Cr(VI) as the electron acceptor in phosphate based M2 salts buffer. After 22 hours almost 27% of Cr(VI) was reduced in the incubations containing active cells relative to the controls containing heat killed cells. Also, in another set of controls with no electron acceptor added, cells showed no increase in cell density during that time demonstrating that the reduction of Cr(VI) by cells of Caulobacter was due to biological activity. Future experiments will investigate the components

  16. Temporal controls of the asymmetric cell division cycle in Caulobacter crescentus.

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    Shenghua Li

    2009-08-01

    Full Text Available The asymmetric cell division cycle of Caulobacter crescentus is orchestrated by an elaborate gene-protein regulatory network, centered on three major control proteins, DnaA, GcrA and CtrA. The regulatory network is cast into a quantitative computational model to investigate in a systematic fashion how these three proteins control the relevant genetic, biochemical and physiological properties of proliferating bacteria. Different controls for both swarmer and stalked cell cycles are represented in the mathematical scheme. The model is validated against observed phenotypes of wild-type cells and relevant mutants, and it predicts the phenotypes of novel mutants and of known mutants under novel experimental conditions. Because the cell cycle control proteins of Caulobacter are conserved across many species of alpha-proteobacteria, the model we are proposing here may be applicable to other genera of importance to agriculture and medicine (e.g., Rhizobium, Brucella.

  17. Biomineralization of Uranium by PhoY Phosphatase Activity Aids Cell Survival in Caulobacter crescentus

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    Yung, M C [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Jiao, Y [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2014-07-22

    Caulobacter crescentus is known to tolerate high levels of uranium [U(VI)], but its detoxification mechanism is poorly understood. Here we show that C. crescentus is able to facilitate U(VI) biomineralization through the formation of U-Pi precipitates via its native alkaline phosphatase activity. The U-Pi precipitates, deposited on the cell surface in the form of meta-autunite structures, have a lower U/Pi ratio than do chemically produced precipitates. The enzyme that is responsible for the phosphatase activity and thus the biomineralization process is identified as PhoY, a periplasmic alkaline phosphatase with broad substrate specificity. Furthermore, PhoY is shown to confer a survival advantage on C. crescentus toward U(VI) under both growth and nongrowth conditions. Results obtained in this study thus highlight U(VI) biomineralization as a resistance mechanism in microbes, which not only improves our understanding of bacterium-mineral interactions but also aids in defining potential ecological niches for metal-resistant bacteria.

  18. Characterization of Uranium Tolerance and Biomineralization Potential of Caulobacter crescentus

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    Park, D.

    2015-12-01

    Due to its high toxicity and mobility, U(VI) poses a major environmental threat to ecosystems. The ubiquitous aerobic bacterium Caulobacter cresecentus is an attractive candidate for U(VI) bioremediation because of its ability to survive in low-nutrient environments (5, 6), tolerate high U concentrations and mineralize U(VI) aerobically through the formation of uranyl phosphate (U-Pi) precipitates. Despite these attractive environmental properties, both a systems level understanding of the adaptive response pathways involved in U tolerance and the environmental conditions affecting the biomineralization process and stability of biogenic U-Pi minerals remain limited. By measuring changes in both mRNA and protein expression during exposure to high U levels, we have identified the core stress response pathways involved in U tolerance. Pathways associated with heat shock, lipospolysaccharide biosynthesis and transport, outer membrane lipoprotein transport and outermembrane assembly were highly induced at both the RNA and protein levels. Correspondingly, removal of integral components of proteolysis pathways including clpA, clpS and degP significantly reduced U tolerance under biomineralization conditions. Surprisingly, in contrast to many other heavy metals, U did not cause oxidative stress or DNA damage. Together, these analyses indicate that U predominately targets the outermembrane and causes mis-folding of both cytoplasmic and extracytoplasmic proteins. Efforts are currently underway to characterize the morphological and structural properties of biogenic U-Pi minerals and the environmental factors that influence their production and stability. Preliminary AFM studies suggest that U-Pi minerals formed under biomineralization conditions appear morphologically distinct from those formed abiotically between U(VI) and inorganic phosphate. Additionally, we observed that biomineralization tolerates a wide pH range (pH 6-9). Our long-range goal is the development of a

  19. Phosphate starvation triggers production and secretion of an extracellular lipoprotein in Caulobacter crescentus.

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    Sophie Le Blastier

    Full Text Available Life in oligotrophic environments necessitates quick adaptive responses to a sudden lack of nutrients. Secretion of specific degradative enzymes into the extracellular medium is a means to mobilize the required nutrient from nearby sources. The aquatic bacterium Caulobacter crescentus must often face changes in its environment such as phosphate limitation. Evidence reported in this paper indicates that under phosphate starvation, C. crescentus produces a membrane surface-anchored lipoprotein named ElpS subsequently released into the extracellular medium. A complete set of 12 genes encoding a type II secretion system (T2SS is located adjacent to the elpS locus in the C. crescentus genome. Deletion of this T2SS impairs release of ElpS in the environment, which surprisingly remains present at the cell surface, indicating that the T2SS is not involved in the translocation of ElpS to the outer membrane but rather in its release. Accordingly, treatment with protease inhibitors prevents release of ElpS in the extracellular medium suggesting that ElpS secretion relies on a T2SS-secreted protease. Finally, secretion of ElpS is associated with an increase in alkaline phosphatase activity in culture supernatants, suggesting a role of the secreted protein in inorganic phosphate mobilization. In conclusion, we have shown that upon phosphate starvation, C. crescentus produces an outer membrane bound lipoprotein, ElpS, which is further cleaved and released in the extracellular medium in a T2SS-dependent manner. Our data suggest that ElpS is associated with an alkaline phosphatase activity, thereby allowing the bacterium to gather inorganic phosphates from a poor environment.

  20. Genome analysis of DNA repair genes in the alpha proteobacterium Caulobacter crescentus

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    Menck Carlos FM

    2007-03-01

    Full Text Available Abstract Background The integrity of DNA molecules is fundamental for maintaining life. The DNA repair proteins protect organisms against genetic damage, by removal of DNA lesions or helping to tolerate them. DNA repair genes are best known from the gamma-proteobacterium Escherichia coli, which is the most understood bacterial model. However, genome sequencing raises questions regarding uniformity and ubiquity of these DNA repair genes and pathways, reinforcing the need for identifying genes and proteins, which may respond to DNA damage in other bacteria. Results In this study, we employed a bioinformatic approach, to analyse and describe the open reading frames potentially related to DNA repair from the genome of the alpha-proteobacterium Caulobacter crescentus. This was performed by comparison with known DNA repair related genes found in public databases. As expected, although C. crescentus and E. coli bacteria belong to separate phylogenetic groups, many of their DNA repair genes are very similar. However, some important DNA repair genes are absent in the C. crescentus genome and other interesting functionally related gene duplications are present, which do not occur in E. coli. These include DNA ligases, exonuclease III (xthA, endonuclease III (nth, O6-methylguanine-DNA methyltransferase (ada gene, photolyase-like genes, and uracil-DNA-glycosylases. On the other hand, the genes imuA and imuB, which are involved in DNA damage induced mutagenesis, have recently been described in C. crescentus, but are absent in E. coli. Particularly interesting are the potential atypical phylogeny of one of the photolyase genes in alpha-proteobacteria, indicating an origin by horizontal transfer, and the duplication of the Ada orthologs, which have diverse structural configurations, including one that is still unique for C. crescentus. Conclusion The absence and the presence of certain genes are discussed and predictions are made considering the particular

  1. Coordination between chromosome replication, segregation, and cell division in Caulobacter crescentus

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    Jensen, Rasmus Bugge

    2006-01-01

    , and the completely replicated terminus regions stay associated with each other after chromosome replication is completed, disassociating very late in the cell cycle shortly before the final cell division event. Invagination of the cytoplasmic membrane occurs earlier than separation of the replicated terminus regions......Progression through the Caulobacter crescentus cell cycle is coupled to a cellular differentiation program. The swarmer cell is replicationally quiescent, and DNA replication initiates at the swarmer-to-stalked cell transition. There is a very short delay between initiation of DNA replication...... and formation of separate nucleoids, which results in trapping of a chromosome on either side of the cell division septum, indicating that there is not a nucleoid exclusion phenotype....

  2. A NAD-dependent glutamate dehydrogenase coordinates metabolism with cell division in Caulobacter crescentus

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    Beaufay, François; Coppine, Jérôme; Mayard, Aurélie; Laloux, Géraldine; De Bolle, Xavier; Hallez, Régis

    2015-01-01

    Coupling cell cycle with nutrient availability is a crucial process for all living cells. But how bacteria control cell division according to metabolic supplies remains poorly understood. Here, we describe a molecular mechanism that coordinates central metabolism with cell division in the α-proteobacterium Caulobacter crescentus. This mechanism involves the NAD-dependent glutamate dehydrogenase GdhZ and the oxidoreductase-like KidO. While enzymatically active GdhZ directly interferes with FtsZ polymerization by stimulating its GTPase activity, KidO bound to NADH destabilizes lateral interactions between FtsZ protofilaments. Both GdhZ and KidO share the same regulatory network to concomitantly stimulate the rapid disassembly of the Z-ring, necessary for the subsequent release of progeny cells. Thus, this mechanism illustrates how proteins initially dedicated to metabolism coordinate cell cycle progression with nutrient availability. PMID:25953831

  3. Multiple large filament bundles observed in Caulobacter crescentus by electron cryotomography

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    Briegel, A; Dias, DP; Li, Z

    2006-01-01

    While the absence of any cytoskeleton was once recognized as a distinguishing feature of prokaryotes, it is now clear that a number of different bacterial proteins do form filaments in vivo. Despite the critical roles these proteins play in cell shape, genome segregation and cell division......, molecular mechanisms have remained obscure in part for lack of electron microscopy-resolution images where these filaments can be seen acting within their cellular context. Here, electron cryotomography was used to image the widely studied model prokaryote Caulobacter crescentus in an intact, near......-native state, producing three-dimensional reconstructions of these cells with unprecedented clarity and fidelity. We observed many instances of large filament bundles in various locations throughout the cell and at different stages of the cell cycle. The bundles appear to fall into four major classes based...

  4. The Caulobacter crescentus phage phiCbK: genomics of a canonical phage

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    Gill Jason J

    2012-10-01

    Full Text Available Abstract Background The bacterium Caulobacter crescentus is a popular model for the study of cell cycle regulation and senescence. The large prolate siphophage phiCbK has been an important tool in C. crescentus biology, and has been studied in its own right as a model for viral morphogenesis. Although a system of some interest, to date little genomic information is available on phiCbK or its relatives. Results Five novel phiCbK-like C. crescentus bacteriophages, CcrMagneto, CcrSwift, CcrKarma, CcrRogue and CcrColossus, were isolated from the environment. The genomes of phage phiCbK and these five environmental phage isolates were obtained by 454 pyrosequencing. The phiCbK-like phage genomes range in size from 205 kb encoding 318 proteins (phiCbK to 280 kb encoding 448 proteins (CcrColossus, and were found to contain nonpermuted terminal redundancies of 10 to 17 kb. A novel method of terminal ligation was developed to map genomic termini, which confirmed termini predicted by coverage analysis. This suggests that sequence coverage discontinuities may be useable as predictors of genomic termini in phage genomes. Genomic modules encoding virion morphogenesis, lysis and DNA replication proteins were identified. The phiCbK-like phages were also found to encode a number of intriguing proteins; all contain a clearly T7-like DNA polymerase, and five of the six encode a possible homolog of the C. crescentus cell cycle regulator GcrA, which may allow the phage to alter the host cell’s replicative state. The structural proteome of phage phiCbK was determined, identifying the portal, major and minor capsid proteins, the tail tape measure and possible tail fiber proteins. All six phage genomes are clearly related; phiCbK, CcrMagneto, CcrSwift, CcrKarma and CcrRogue form a group related at the DNA level, while CcrColossus is more diverged but retains significant similarity at the protein level. Conclusions Due to their lack of any apparent relationship to

  5. Regulation of the activity of the dual-function DnaA protein in Caulobacter crescentus.

    Directory of Open Access Journals (Sweden)

    Carmen Fernandez-Fernandez

    Full Text Available DnaA is a conserved essential bacterial protein that acts as the initiator of chromosomal replication as well as a master transcriptional regulator in Caulobacter crescentus. Thus, the intracellular levels of active DnaA need to be tightly regulated during the cell cycle. Our previous work suggested that DnaA may be regulated at the level of its activity by the replisome-associated protein HdaA. Here, we describe the construction of a mutant DnaA protein [DnaA(R357A]. The R357 residue in the AAA+ domain of the C. crescentus DnaA protein is equivalent to the R334 residue of the E. coli DnaA protein, which is required for the Regulatory Inactivation of DnaA (RIDA. We found that the expression of the DnaA(R357A mutant protein in C. crescentus, but not the expression of the wild-type DnaA protein at similar levels, causes a severe phenotype of over-initiation of chromosomal replication and that it blocks cell division. Thus, the mutant DnaA(R357A protein is hyper-active to promote the initiation of DNA replication, compared to the wild-type DnaA protein. DnaA(R357A could not replace DnaA in vivo, indicating that the switch in DnaA activity once chromosomal replication has started may be an essential process in C. crescentus. We propose that the inactivation of DnaA is the main mechanism ensuring that chromosomal replication starts only once per cell cycle. We further observed that the R357A substitution in DnaA does not promote the activity of DnaA as a direct transcriptional activator of four important genes, encoding HdaA, the GcrA master cell cycle regulator, the FtsZ cell division protein and the MipZ spatial regulator of cell division. Thus, the AAA+ domain of DnaA may play a role in temporally regulating the bifunctionality of DnaA by reallocating DnaA molecules from initiating DNA replication to transcribing genes within the unique DnaA regulon of C. crescentus.

  6. The Caulobacter crescentus phage phiCbK: genomics of a canonical phage

    Science.gov (United States)

    2012-01-01

    Background The bacterium Caulobacter crescentus is a popular model for the study of cell cycle regulation and senescence. The large prolate siphophage phiCbK has been an important tool in C. crescentus biology, and has been studied in its own right as a model for viral morphogenesis. Although a system of some interest, to date little genomic information is available on phiCbK or its relatives. Results Five novel phiCbK-like C. crescentus bacteriophages, CcrMagneto, CcrSwift, CcrKarma, CcrRogue and CcrColossus, were isolated from the environment. The genomes of phage phiCbK and these five environmental phage isolates were obtained by 454 pyrosequencing. The phiCbK-like phage genomes range in size from 205 kb encoding 318 proteins (phiCbK) to 280 kb encoding 448 proteins (CcrColossus), and were found to contain nonpermuted terminal redundancies of 10 to 17 kb. A novel method of terminal ligation was developed to map genomic termini, which confirmed termini predicted by coverage analysis. This suggests that sequence coverage discontinuities may be useable as predictors of genomic termini in phage genomes. Genomic modules encoding virion morphogenesis, lysis and DNA replication proteins were identified. The phiCbK-like phages were also found to encode a number of intriguing proteins; all contain a clearly T7-like DNA polymerase, and five of the six encode a possible homolog of the C. crescentus cell cycle regulator GcrA, which may allow the phage to alter the host cell’s replicative state. The structural proteome of phage phiCbK was determined, identifying the portal, major and minor capsid proteins, the tail tape measure and possible tail fiber proteins. All six phage genomes are clearly related; phiCbK, CcrMagneto, CcrSwift, CcrKarma and CcrRogue form a group related at the DNA level, while CcrColossus is more diverged but retains significant similarity at the protein level. Conclusions Due to their lack of any apparent relationship to other described phages, this

  7. SMC Progressively Aligns Chromosomal Arms in Caulobacter crescentus but Is Antagonized by Convergent Transcription

    Directory of Open Access Journals (Sweden)

    Ngat T. Tran

    2017-08-01

    Full Text Available The structural maintenance of chromosomes (SMC complex plays an important role in chromosome organization and segregation in most living organisms. In Caulobacter crescentus, SMC is required to align the left and the right arms of the chromosome that run in parallel down the long axis of the cell. However, the mechanism of SMC-mediated alignment of chromosomal arms remains elusive. Here, using genome-wide methods and microscopy of single cells, we show that Caulobacter SMC is recruited to the centromeric parS site and that SMC-mediated arm alignment depends on the chromosome-partitioning protein ParB. We provide evidence that SMC likely tethers the parS-proximal regions of the chromosomal arms together, promoting arm alignment. Furthermore, we show that highly transcribed genes near parS that are oriented against SMC translocation disrupt arm alignment, suggesting that head-on transcription interferes with SMC translocation. Our results demonstrate a tight interdependence of bacterial chromosome organization and global patterns of transcription.

  8. Modulation of medium pH by Caulobacter crescentus facilitates recovery from uranium-induced growth arrest.

    Science.gov (United States)

    Park, Dan M; Jiao, Yongqin

    2014-09-01

    The oxidized form of uranium [U(VI)] predominates in oxic environments and poses a major threat to ecosystems. Due to its ability to mineralize U(VI), the oligotroph Caulobacter crescentus is an attractive candidate for U(VI) bioremediation. However, the physiological basis for U(VI) tolerance is unclear. Here we demonstrated that U(VI) caused a temporary growth arrest in C. crescentus and three other bacterial species, although the duration of growth arrest was significantly shorter for C. crescentus. During the majority of the growth arrest period, cell morphology was unaltered and DNA replication initiation was inhibited. However, during the transition from growth arrest to exponential phase, cells with shorter stalks were observed, suggesting a decoupling between stalk development and the cell cycle. Upon recovery from growth arrest, C. crescentus proliferated with a growth rate comparable to that of a control without U(VI), although a fraction of these cells appeared filamentous with multiple replication start sites. Normal cell morphology was restored by the end of exponential phase. Cells did not accumulate U(VI) resistance mutations during the prolonged growth arrest, but rather, a reduction in U(VI) toxicity occurred concomitantly with an increase in medium pH. Together, these data suggest that C. crescentus recovers from U(VI)-induced growth arrest by reducing U(VI) toxicity through pH modulation. Our finding represents a unique U(VI) detoxification strategy and provides insight into how microbes cope with U(VI) under nongrowing conditions, a metabolic state that is prevalent in natural environments. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  9. An essential thioredoxin is involved in the control of the cell cycle in the bacteriumCaulobacter crescentus.

    Science.gov (United States)

    Goemans, Camille V; Beaufay, François; Wahni, Khadija; Van Molle, Inge; Messens, Joris; Collet, Jean-François

    2018-03-09

    Thioredoxins (Trxs) are antioxidant proteins that are conserved among all species. These proteins have been extensively studied and perform reducing reactions on a broad range of substrates. Here, we identified Caulobacter crescentus Trx1 (CCNA_03653; Cc Trx1) as an oxidoreductase that is involved in the cell cycle progression of this model bacterium and is required to sustain life. Intriguingly, the abundance of Cc Trx1 varies throughout the C. crescentus cell cycle: although the expression of Cc Trx1 is induced in stalked cells, right before DNA replication initiation, Cc Trx1 is actively degraded by the ClpXP protease in predivisional cells. Importantly, we demonstrated that regulation of the abundance of Cc Trx1 is crucial for cell growth and survival as modulating Cc Trx1 levels leads to cell death. Finally, we also report a comprehensive biochemical and structural characterization of this unique and essential Trx. The requirement to precisely control the abundance of Cc Trx1 for cell survival underlines the importance of redox control for optimal cell cycle progression in C. crescentus . © 2018 by The American Society for Biochemistry and Molecular Biology, Inc.

  10. The cloning, expression, purification, characterization and modeled structure of Caulobacter crescentus β-Xylosidase I.

    Science.gov (United States)

    Graciano, Luciana; Corrêa, Juliana Moço; Gandra, Rinaldo Ferreira; Seixas, Flavio Augusto Vicente; Kadowaki, Marina Kimiko; Sampaio, Silvio César; Silva, José Luis da Conceição; Osaku, Clarice Aoki; Simão, Rita de Cássia Garcia

    2012-09-01

    The xynB1 gene (CCNA 01040) of Caulobacter crescentus that encodes a bifunctional enzyme containing the conserved β-Xylosidase and α-L-Arabinofuranosidase (β-Xyl I-α-L-Ara) domains was amplified by PCR and cloned into the vector pJet1.2Blunt. The xynB1 gene was subcloned into the vector pPROEX-hta that produces a histidine-fused translation product. The overexpression of recombinant β-Xyl I-α-L-Ara was induced with IPTG in BL21 (DE3) and the resulting intracellular protein was purified with pre-packaged nickel-Sepharose columns. The recombinant β-Xyl I-α-L-Ara exhibited a specific β-Xylosidase I activity of 1.25 U mg(-1) to oNPX and a specific α-L-Arabinofuranosidase activity of 0.47 U mg(-1) to pNPA. The predominant activity of the recombinant enzyme was its β-Xylosidase I activity, and the enzymatic characterization was focused on it. The β-Xylosidase I activity was high over the pH range 3-10, with maximal activity at pH 6. The enzyme activity was optimal at 45 °C, and a high degree of stability was verified over 240 min at this temperature. Moreover, β-Xylosidase activity was inhibited in the presence of the metals Zn(2+) and Cu(2+), and the enzyme exhibited K(M) and V(Max) values of 2.89 ± 0.13 mM and 1.4 ± 0.04 μM min(-1) to oNPX, respectively. The modeled structure of β-xylosidase I showed that its active site is highly conserved compared with other structures of the GH43 family. The increase in the number of contact residues responsible for maintaining the dimeric structure indicates that this dimer is more stable than the tetramer form.

  11. The Caulobacter crescentus transducing phage Cr30 is a unique member of the T4-like family of myophages.

    Science.gov (United States)

    Ely, Bert; Gibbs, Whitney; Diez, Simon; Ash, Kurt

    2015-06-01

    Bacteriophage Cr30 has proven useful for the transduction of Caulobacter crescentus. Nucleotide sequencing of Cr30 DNA revealed that the Cr30 genome consists of 155,997 bp of DNA that codes for 287 proteins and five tRNAs. In contrast to the 67 % GC content of the host genome, the GC content of the Cr30 genome is only 38 %. This lower GC content causes both the codon usage pattern and the amino acid composition of the Cr30 proteins to be quite different from those of the host bacteria. As a consequence, the Cr30 mRNAs probably are translated at a rate that is slower than the normal rate for host mRNAs. A phylogenetic comparison of the genome indicates that Cr30 is a member of the T4-like family that is most closely related to a new group of T-like phages exemplified by фM12.

  12. Involvement of organic acids and amino acids in ameliorating Ni(II) toxicity induced cell cycle dysregulation in Caulobacter crescentus: a metabolomics analysis.

    Science.gov (United States)

    Jain, Abhishek; Chen, Wei Ning

    2018-04-03

    Nickel (Ni(II)) toxicity is addressed by many different bacteria, but bacterial responses to nickel stress are still unclear. Therefore, we studied the effect of Ni(II) toxicity on cell proliferation of α-proteobacterium Caulobacter crescentus. Next, we showed the mechanism that allows C. crescentus to survive in Ni(II) stress condition. Our results revealed that the growth of C. crescentus is severely affected when the bacterium was exposed to different Ni(II) concentrations, 0.003 mM slightly affected the growth, 0.008 mM reduced the growth by 50%, and growth was completely inhibited at 0.015 mM. It was further shown that Ni(II) toxicity induced mislocalization of major regulatory proteins such as MipZ, FtsZ, ParB, and MreB, resulting in dysregulation of the cell cycle. GC-MS metabolomics analysis of Ni(II) stressed C. crescentus showed an increased level of nine important metabolites including TCA cycle intermediates and amino acids. This indicates that changes in central carbon metabolism and nitrogen metabolism are linked with the disruption of cell division process. Addition of malic acid, citric acid, alanine, proline, and glutamine to 0.015 mM Ni(II)-treated C. crescentus restored its growth. Thus, the present work shows a protective effect of these organic acids and amino acids on Ni(II) toxicity. Metabolic stimulation through the PutA/GlnA pathway, accelerated degradation of CtrA, and Ni-chelation by organic acids or amino acids are some of the possible mechanisms suggested to be involved in enhancing C. crescentus's tolerance. Our results shed light on the mechanism of increased Ni(II) tolerance in C. crescentus which may be useful in bioremediation strategies and synthetic biology applications such as the development of whole cell biosensor.

  13. Turning off flagellum rotation requires the pleiotropic gene pleD: pleA, pleC, and pleD define two morphogenic pathways in Caulobacter crescentus.

    OpenAIRE

    Sommer, J M; Newton, A

    1989-01-01

    We have identified mutations in three pleiotropic genes, pleA, pleC, and pleD, that are required for differentiation in Caulobacter crescentus. pleA and pleC mutants were isolated in an extensive screen for strains defective in both motility and adsorption of polar bacteriophage phi CbK; using temperature-sensitive alleles, we determined the time at which the two genes act. pleA was required for a short period at 0.7 of the swarmer cell cycle for flagellum biosynthesis, whereas pleC was requi...

  14. Activation and polar sequestration of PopA, a c-di-GMP effector protein involved in Caulobacter crescentus cell cycle control

    DEFF Research Database (Denmark)

    Ozaki, Shogo; Schalch-Moser, Annina; Zumthor, Ludwig

    2014-01-01

    When Caulobacter crescentus enters S-phase the replication initiation inhibitor CtrA dynamically positions to the old cell pole to be degraded by the polar ClpXP protease. Polar delivery of CtrA requires PopA and the diguanylate cyclase PleD that positions to the same pole. Here we present evidence...... that PopA originated through gene duplication from its paralogue response regulator PleD and subsequent co-option as c-di-GMP effector protein. While the C-terminal catalytic domain (GGDEF) of PleD is activated by phosphorylation of the N-terminal receiver domain, functional adaptation has reversed signal......A to the cell pole in response to c-di-GMP binding. In agreement with the divergent activation and targeting mechanisms, distinct markers sequester PleD and PopA to the old cell pole upon S-phase entry. Together these data indicate that PopA adopted a novel role as topology specificity factor to help recruit...

  15. Analysis of the xynB5 gene encoding a multifunctional GH3-BglX β-glucosidase-β-xylosidase-α-arabinosidase member in Caulobacter crescentus.

    Science.gov (United States)

    Justo, Priscila Innocenti; Corrêa, Juliana Moço; Maller, Alexandre; Kadowaki, Marina Kimiko; da Conceição-Silva, José Luis; Gandra, Rinaldo Ferreira; Simão, Rita de Cássia Garcia

    2015-10-01

    The Caulobacter crescentus (NA1000) xynB5 gene (CCNA_03149) encodes a predicted β-glucosidase-β-xylosidase enzyme that was amplified by polymerase chain reaction; the product was cloned into the blunt ends of the pJet1.2 plasmid. Analysis of the protein sequence indicated the presence of conserved glycosyl hydrolase 3 (GH3), β-glucosidase-related glycosidase (BglX) and fibronectin type III-like domains. After verifying its identity by DNA sequencing, the xynB5 gene was linked to an amino-terminal His-tag using the pTrcHisA vector. A recombinant protein (95 kDa) was successfully overexpressed from the xynB5 gene in E. coli Top 10 and purified using pre-packed nickel-Sepharose columns. The purified protein (BglX-V-Ara) demonstrated multifunctional activities in the presence of different substrates for β-glucosidase (pNPG: p-nitrophenyl-β-D-glucoside) β-xylosidase (pNPX: p-nitrophenyl-β-D-xyloside) and α-arabinosidase (pNPA: p-nitrophenyl-α-L-arabinosidase). BglX-V-Ara presented an optimal pH of 6 for all substrates and optimal temperature of 50 °C for β-glucosidase and α-L-arabinosidase and 60 °C for β-xylosidase. BglX-V-Ara predominantly presented β-glucosidase activity, with the highest affinity for its substrate and catalytic efficiency (Km 0.24 ± 0.0005 mM, Vmax 0.041 ± 0.002 µmol min(-1) mg(-1) and Kcat/Km 0.27 mM(-1) s(-1)), followed by β-xylosidase (Km 0.64 ± 0.032 mM, Vmax 0.055 ± 0.002 µmol min(-1) mg(-1) and Kcat/Km 0.14 mM(-1)s(-1)) and finally α-L-arabinosidase (Km 1.45 ± 0.05 mM, Vmax 0.091 ± 0.0004 µmol min(-1) mg(-1) and Kcat/Km 0.1 mM(-1) s(-1)). To date, this is the first report to demonstrate the characterization of a GH3-BglX family member in C. crescentus that may have applications in biotechnological processes (i.e., the simultaneous saccharification process) because the multifunctional enzyme could play an important role in bacterial hemicellulose degradation.

  16. Cloning and expression of the xynA1 gene encoding a xylanase of the GH10 group in Caulobacter crescentus.

    Science.gov (United States)

    Graciano, Luciana; Corrêa, Juliana Moço; Vieira, Fabíola Giovanna Nesello; Bosetto, Adilson; Loth, Eduardo Alexandre; Kadowaki, Marina Kimiko; Gandra, Rinaldo Ferreira; Simão, Rita de Cássia Garcia

    2015-04-01

    Caulobacter crescentus (NA1000 strain) are aquatic bacteria that can live in environments of low nutritional quality and present numerous genes that encode enzymes involved in plant cell wall deconstruction, including five genes for β-xylosidases (xynB1-xynB5) and three genes for xylanases (xynA1-xynA3). The overall activity of xylanases in the presence of different agro-industrial residues was evaluated, and it was found that the residues from the processing of corn were the most efficient in inducing bacterial xylanases. The xynA1 gene (CCNA_02894) encoding a predicted xylanase of group 10 of glyco-hydrolases (GH10) that was efficiently overexpressed in Escherichia coli LMG194 using 0.02 % arabinose, after cloning into the vector pJet1.2blunt and subcloning into the expression vector pBAD/gIII, provided a fusion protein that contained carboxy-terminal His-tags, named XynA1. The characterization of pure XynA1 showed an enzymatic activity of 18.26 U mL(-1) and a specific activity of 2.22 U mg-(1) in the presence of xylan from beechwood as a substrate. XynA1 activity was inhibited by EDTA and metal ions such as Cu(2+) and Mg(2+). By contrast, β-mercaptoethanol, dithiothreitol (DTT), and Ca(2+) induced recombinant enzyme activity. Kinetic data for XynA1 revealed K M and V max values of 3.77 mg mL-(1) and 10.20 μM min-(1), respectively. Finally, the enzyme presented an optimum pH of 6 and an optimum temperature of 50 °C. In addition, 80 % of the activity of XynA1 was maintained at 50 °C for 4 h of incubation, suggesting a thermal stability for the biotechnological processes. This work is the first study concerning the cloning, overexpression, and enzymatic characterization of C. crescentus xylanase.

  17. Crystallization and X-ray diffraction analysis of an l-arabinonate dehydratase from Rhizobium leguminosarum bv. trifolii and a d-xylonate dehydratase from Caulobacter crescentus

    Energy Technology Data Exchange (ETDEWEB)

    Rahman, Mohammad Mubinur [University of Eastern Finland, Joensuu Campus, PO Box 111, FIN-80101 Joensuu (Finland); Andberg, Martina; Koivula, Anu [VTT Technical Research Centre of Finland Ltd, PO Box 1000, FIN-02044 VTT Espoo (Finland); Rouvinen, Juha; Hakulinen, Nina, E-mail: nina.hakulinen@uef.fi [University of Eastern Finland, Joensuu Campus, PO Box 111, FIN-80101 Joensuu (Finland)

    2016-07-13

    l-Arabinonate dehydratase and d-xylonate dehydratase from the IlvD/EDD family were crystallized by the vapour-diffusion method. Diffraction data sets were collected to resolutions of 2.40 and 2.66 Å from crystals of l-arabinonate dehydratase and d-xylonate dehydratase, respectively. l-Arabinonate dehydratase (EC 4.2.1.25) and d-xylonate dehydratase (EC 4.2.1.82) are two enzymes that are involved in a nonphosphorylative oxidation pathway of pentose sugars. l-Arabinonate dehydratase converts l-arabinonate into 2-dehydro-3-deoxy-l-arabinonate, and d-xylonate dehydratase catalyzes the dehydration of d-xylonate to 2-dehydro-3-deoxy-d-xylonate. l-Arabinonate and d-xylonate dehydratases belong to the IlvD/EDD family, together with 6-phosphogluconate dehydratases and dihydroxyacid dehydratases. No crystal structure of any l-arabinonate or d-xylonate dehydratase is available in the PDB. In this study, recombinant l-arabinonate dehydratase from Rhizobium leguminosarum bv. trifolii (RlArDHT) and d-xylonate dehydratase from Caulobacter crescentus (CcXyDHT) were heterologously expressed in Escherichia coli and purified by the use of affinity chromatography followed by gel-filtration chromatography. The purified proteins were crystallized using the hanging-drop vapour-diffusion method at 293 K. Crystals of RlArDHT that diffracted to 2.40 Å resolution were obtained using sodium formate as a precipitating agent. They belonged to space group P2{sub 1}, with unit-cell parameters a = 106.07, b = 208.61, c = 147.09 Å, β = 90.43°. Eight RlArDHT molecules (two tetramers) in the asymmetric unit give a V{sub M} value of 3.2 Å{sup 3} Da{sup −1} and a solvent content of 62%. Crystals of CcXyDHT that diffracted to 2.66 Å resolution were obtained using sodium formate and polyethylene glycol 3350. They belonged to space group C2, with unit-cell parameters a = 270.42, b = 236.13, c = 65.17 Å, β = 97.38°. Four CcXyDHT molecules (a tetramer) in the asymmetric unit give a V{sub M

  18. Depletion of the xynB2 gene upregulates β-xylosidase expression in C. crescentus.

    Science.gov (United States)

    Corrêa, Juliana Moço; Mingori, Moara Rodrigues; Gandra, Rinaldo Ferreira; Loth, Eduardo Alexandre; Seixas, Flávio Augusto Vicente; Simão, Rita de Cássia Garcia

    2014-01-01

    Caulobacter crescentus is able to express several enzymes involved in the utilization of lignocellulosic biomasses. Five genes, xynB1-5, that encode β-xylosidases are present in the genome of this bacterium. In this study, the xynB2 gene, which encodes β-xylosidase II (CCNA_02442), was cloned under the control of the PxylX promoter to generate the O-xynB2 strain, which overexpresses the enzyme in the presence of xylose. In addition, a null mutant strain, Δ-xynB2, was created by two homologous recombination events where the chromosomal xynB2 gene was replaced by a copy that was disrupted by the spectinomycin-resistant cassette. We demonstrated that C. crescentus cells lacking β-xylosidase II upregulates the xynB genes inducing β-xylosidase activity. Transcriptional analysis revealed that xynB1 (RT-PCR analysis) and xynB2 (lacZ transcription fusion) gene expression was induced in the Δ-xynB2 cells, and high β-xylosidase activity was observed in the presence of different agro-industrial residues in the null mutant strain, a characteristic that can be explored and applied in biotechnological processes. In contrast, overexpression of the xynB2 gene caused downregulation of the expression and activity of the β-xylosidase. For example, the β-xylosidase activity that was obtained in the presence of sugarcane bagasse was 7-fold and 16-fold higher than the activity measured in the C. crescentus parental and O-xynB2 cells, respectively. Our results suggest that β-xylosidase II may have a role in controlling the expression of the xynB1 and xynB2 genes in C. crescentus.

  19. Distinct constrictive processes, separated in time and space,divide Caulobacter inner and outer membranes

    Energy Technology Data Exchange (ETDEWEB)

    Judd, Ellen M.; Comolli, Luis R.; Chen, Joseph C.; Downing,Kenneth H.; Moerner, W.E.; McAdams, Harley H.

    2005-05-01

    Cryo-electron microscope tomography (cryoEM) and a fluorescence loss in photobleaching (FLIP) assay were used to characterize progression of the terminal stages of Caulobacter crescentus cell division. Tomographic cryoEM images of the cell division site show separate constrictive processes closing first the inner, and then the outer, membrane in a manner distinctly different from septum-forming bacteria. The smallest observed pre-fission constrictions were 60 nm for both the inner and outer membrane. FLIP experiments had previously shown cytoplasmic compartmentalization, when cytoplasmic proteins can no longer diffuse between the two nascent progeny cell compartments, occurring 18 min before daughter cell separation in a 135 min cell cycle. Here, we used FLIP experiments with membrane-bound and periplasmic fluorescent proteins to show that (1) periplasmic compartmentalization occurs after cytoplasmic compartmentalization, consistent with the cryoEM observations, and (2) inner membrane and periplasmic proteins can diffuse past the FtsZ constriction site, indicating that the cell division machinery does not block membrane diffusion.

  20. Report of the first human case of Caulobacter sp. infection

    DEFF Research Database (Denmark)

    Justesen, Ulrik S; Holt, Hanne M; Thiesson, Helle

    2007-01-01

    A Caulobacter sp. isolate was recovered from the dialysis fluid of a patient undergoing peritoneal dialysis. Bacterial identification included electron microscopy and 16S rDNA sequencing. To our knowledge, this is the first report of human Caulobacter infection. Special growth requirements sugges...

  1. Growth Conditions Regulate the Requirements for Caulobacter Chromosome Segregation

    DEFF Research Database (Denmark)

    Shebelut, Conrad W.; Jensen, Rasmus Bugge; Gitai, Zemer

    2009-01-01

    Growth environments are important metabolic and developmental regulators. Here we demonstrate a growth environment-dependent effect on Caulobacter chromosome segregation of a small-molecule inhibitor of the MreB bacterial actin cytoskeleton. Our results also implicate ParAB as important segregation...... determinants, suggesting that multiple distinct mechanisms can mediate Caulobacter chromosome segregation and that their relative contributions can be environmentally regulated....

  2. Conserved S-Layer-Associated Proteins Revealed by Exoproteomic Survey of S-Layer-Forming Lactobacilli

    Science.gov (United States)

    Johnson, Brant R.; Hymes, Jeffrey; Sanozky-Dawes, Rosemary; Henriksen, Emily DeCrescenzo

    2015-01-01

    The Lactobacillus acidophilus homology group comprises Gram-positive species that include L. acidophilus, L. helveticus, L. crispatus, L. amylovorus, L. gallinarum, L. delbrueckii subsp. bulgaricus, L. gasseri, and L. johnsonii. While these bacteria are closely related, they have varied ecological lifestyles as dairy and food fermenters, allochthonous probiotics, or autochthonous commensals of the host gastrointestinal tract. Bacterial cell surface components play a critical role in the molecular dialogue between bacteria and interaction signaling with the intestinal mucosa. Notably, the L. acidophilus complex is distinguished in two clades by the presence or absence of S-layers, which are semiporous crystalline arrays of self-assembling proteinaceous subunits found as the outermost layer of the bacterial cell wall. In this study, S-layer-associated proteins (SLAPs) in the exoproteomes of various S-layer-forming Lactobacillus species were proteomically identified, genomically compared, and transcriptionally analyzed. Four gene regions encoding six putative SLAPs were conserved in the S-layer-forming Lactobacillus species but not identified in the extracts of the closely related progenitor, L. delbrueckii subsp. bulgaricus, which does not produce an S-layer. Therefore, the presence or absence of an S-layer has a clear impact on the exoproteomic composition of Lactobacillus species. This proteomic complexity and differences in the cell surface properties between S-layer- and non-S-layer-forming lactobacilli reveal the potential for SLAPs to mediate intimate probiotic interactions and signaling with the host intestinal mucosa. PMID:26475115

  3. S-layer architectures : extending the morphogenetic potential of S-layer protein self-assembly

    International Nuclear Information System (INIS)

    Schuster, D.

    2013-01-01

    Self-assembly of molecular building blocks is a common principle for bottom up based building principles in nature. One example are crystalline bacterial surface layers, termed S-layers, which are the most commonly observed cell surface structures in prokaryotic organisms. They recrystallize into highly ordered, porous protein meshworks with unit cell sizes of 3 to 30 nm and pore sizes of 2 to 8 nm. In this work, S-layers were self-assembled on various three dimensional scaffolds in order to fabricate novel S-layer architectures. Exploiting the stabilizing effect of silica deposited on the S-layer protein meshwork led to the construction of hollow S-layer nano-containers derived from coated liposomes. Transmission electron microscopy (TEM) techniques and release experiments with fluorescent dyes confirmed the dissolution of the supporting lipids. Silica deposition on different spherical particles in solution, as well as on planar S-layer coated surfaces, could be monitored by measuring the ζ-potential, the decline of monosilicic acid in solution, by using scanning electron microscopy (SEM) with energy dispersive X-ray (EDX) analysis or by quartz crystal microbalance with dissipation monitoring (QCM-D). Both, ζ-potential and release experiments showed differences between silicified plain liposomes and silicified S-layer coated liposomes. In addition, nanocapsules with calcium carbonate cores served as another template for the construction of silica supported S-layer architectures. These were investigated by SEM and fluorescence microscopy after fluorescence labeling. Additional coating with polyelectrolytes increased the stability of the nanocapsules. Their mechanical properties were characterized by atomic force microscopy (AFM). The influence of silica deposition was investigated by AFM and SEM. Further on, emulsomes and gas filled lipid supported microbubbles may serve as other templates for the design of spherical protein constructs although extraction of the

  4. Caulobacter Species as a Cause of Postneurosurgical Bacterial Meningitis in a Pediatric Patient

    Directory of Open Access Journals (Sweden)

    Natalie Bridger

    2012-01-01

    Full Text Available Caulobacter species have been rarely found to be a cause of human infection. A case of probable Caulobacter species meningitis occurring postneurosurgery in a pediatric patient is reported in the present article. Gram stain and colony morphology of the isolate were not consistent with the identification provided by commercial phenotypic identification systems. The present case illustrates the need to reconcile conflicting phenotypic test results using 16S ribosomal DNA sequencing.

  5. ORF Alignment: NC_002696 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available Caulobacter crescentus ... Length = 110 ... Query: 11 ... PPPGTVLCGLDEIASPGSKGFR...WREGDAMFAGFVVRKGEALVGYVDSCPHAGWPLAGFAG 70 ... PPPGTVLCGLDEIASPGSKGFRWREGDAMFAGFVVRKGEALVGYVDSCPHAGWPL...AGFAG Sbjct: 1 ... PPPGTVLCGLDEIASPGSKGFRWREGDAMFAGFVVRKGEALVGYVDSCPHAGWPLAGFAG 60 ...

  6. ORF Alignment: NC_002696 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available NC_002696 gi|16126641 >1uzbA 58 515 12 462 8e-77 ... ref|NP_421205.1| vanillin dehydr...ogenase [Caulobacter crescentus CB15] gb|AAK24373.1| ... vanillin dehydrogenase [Caulobacter crescent...us CB15] ... pir||A87547 vanillin dehydrogenase [imported] - ... Caulobacter crescentus ...

  7. ORF Alignment: NC_003317 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available ... regulator, internal deletion [Caulobacter crescentus ... CB15] pir||A87693 transcription regulato... NC_003317 gi|17988031 >1etoB 1 97 211 307 4e-07 ... ref|NP_422373.1| transcriptional regulator, internal delet...r, internal ... deletion [imported] - Caulobacter crescentus ... Len...ion [Caulobacter ... crescentus CB15] gb|AAK25541.1| transcriptional ...

  8. ORF Alignment: NC_002696 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available ... regulator, internal deletion [Caulobacter crescentus ... CB15] pir||A87693 transcription regulato... NC_002696 gi|16127809 >1etoB 1 97 211 307 4e-07 ... ref|NP_422373.1| transcriptional regulator, internal delet...r, internal ... deletion [imported] - Caulobacter crescentus ... Len...ion [Caulobacter ... crescentus CB15] gb|AAK25541.1| transcriptional ...

  9. S-Layer-Based Nanocomposites for Industrial Applications.

    Science.gov (United States)

    Raff, Johannes; Matys, Sabine; Suhr, Matthias; Vogel, Manja; Günther, Tobias; Pollmann, Katrin

    2016-01-01

    This chapter covers the fundamental aspects of bacterial S-layers: what are S-layers, what is known about them, and what are their main features that makes them so interesting for the production of nanostructures. After a detailed introduction of the paracrystalline protein lattices formed by S-layer systems in nature the chapter explores the engineering of S-layer-based materials. How can S-layers be used to produce "industry-ready" nanoscale bio-composite materials, and which kinds of nanomaterials are possible (e.g., nanoparticle synthesis, nanoparticle immobilization, and multifunctional coatings)? What are the advantages and disadvantages of S-layer-based composite materials? Finally, the chapter highlights the potential of these innovative bacterial biomolecules for future technologies in the fields of metal filtration, catalysis, and bio-functionalization.

  10. Genome Sequence of Selenium-Solubilizing Bacterium Caulobacter vibrioides T5M6

    DEFF Research Database (Denmark)

    Wang, Yihua; Qin, Yanan; Kot, Witold

    2016-01-01

    Caulobacter vibrioides T5M6 is a Gram-negative strain that strongly solubilizes selenium (Se) mineral into Se(IV) and was isolated from a selenium mining area in Enshi, southwest China. This strain produces the phytohormone IAA and promotes plant growth. Here we present the genome of this strain...

  11. Biogenesis and functions of bacterial S-layers.

    OpenAIRE

    Fagan, R.P.; Fairweather, N.F.

    2014-01-01

    The outer surface of many archaea and bacteria is coated with a proteinaceous surface layer (known as an S-layer), which is formed by the self-assembly of monomeric proteins into a regularly spaced, two-dimensional array. Bacteria possess dedicated pathways for the secretion and anchoring of the S-layer to the cell wall, and some Gram-positive species have large S-layer-associated gene families. S-layers have important roles in growth and survival, and their many functions include the mainten...

  12. Physical and functional S-layer reconstitution in Aeromonas salmonicida.

    Science.gov (United States)

    Garduño, R A; Phipps, B M; Kay, W W

    1995-05-01

    The various functions attributed to the S-layer of Aeromonas salmonicida have been previously identified by their conspicuous absence in S-layer-defective mutants. As a different approach to establish the multifunctional nature of this S-layer, we established methods for reconstitution of the S-layer of A. salmonicida. Then we investigated the functional competence of the reconstituted S-layer. S-layers were reconstituted in different systems: on inert membranes or immobilized lipopolysaccharide (LPS) from purified S-layer protein (A-protein) or on viable cells from either A-protein or preassembled S-layer sheets. In the absence of divalent cations and LPS, purified A-protein in solution spontaneously assembled into tetrameric oligomers and, upon concentration by ultrafiltration, into macroscopic, semicrystalline sheets formed by oligomers loosely organized in a tetragonal arrangement. In the presence of Ca2+, purified A-protein assembled into normal tetragonal arrays of interlocked subunits. A-protein bound with high affinity (Kd, 1.55 x 10(-7) M) and specificity to high-molecular-weight LPS from A. salmonicida but not to the LPSs of several other bacterial species. In vivo, A-protein could be reconstituted only on A. salmonicida cells which contained LPS, and Ca2+ affected both a regular tetragonal organization of the reattached A-protein and an enhanced reattachment of the A-protein to the cell surface. The reconstitution of preformed S-layer sheets (produced by an S-layer-secreting mutant) to an S-layer-negative mutant occurred consistently and efficiently when the two mutant strains were cocultured on calcium-replete solid media. Reattached A-protein (exposed on the surface of S-layer-negative mutants) was able to bind porphyrins and an S-layer-specific phage but largely lacked regular organization, as judged by its inability to bind immunoglobulins. Reattached S-layer sheets were regularly organized and imparted the properties of porphyrin binding

  13. Caulobacter hibisci sp. nov., isolated from rhizosphere of Hibiscus syriacus L. (Mugunghwa flower).

    Science.gov (United States)

    Moya, Gabriela; Yan, Zheng-Fei; Won, KyungHwa; Yang, Jung-Eun; Wang, Qi-Jun; Kook, MooChang; Yi, Tae-Hoo

    2017-09-01

    A Gram-stain-negative, smooth, bright yellow-pigmented, aerobic, catalase- and oxidase-positive and rod-shaped bacterial strain was isolated from rhizosphere of Hibiscus syriacus L. (Mugunghwa flower) located in Kyung Hee University, Yongin, Gyeonggi, South Korea. Cells were dimorphic, non-motile or non-stalked, and motile by means of peritrichous flagellum. The strain, named THG-AG3.4T, grew at 15-35 °C, at pH 6.5-9.0 and in the presence of 0-1.5 % (w/v) NaCl. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain THG-AG3.4T was most closely related to Caulobacter segnis ATCC 21756T (98.64 % similarity), Caulobacter vibrioides CB51T (98.57 %) and Caulobacter henricii ATCC 15253T (97.41 %). The DNA G+C content of strain THG-AG3.4T was 64.0 mol%. In DNA-DNA hybridization, the DNA-DNA relatedness between strain THG-AG3.4T and its closest phylogenetic neighbour was below 55.0 %. The predominant isoprenoid quinone detected in strain THG-AG3.4T was ubiquinone-10 (Q-10). The major polar lipids were found to be an unidentified lipid, two unidentified phosphoglycolipids, five unidentified glycolipids, eight unidentified aminolipids and phosphatidylglycerol. The major fatty acids were C16 : 0, summed feature 3 (C16 : 1ω7c and/or C16 : 1ω6c) and summed feature 8 (C18 : 1ω7c and/or C18 : 1ω6c). Thus, based on the report of the phenotypic, genotypic and phylogenetic characterization of strain THG-AG3.4T, it has been concluded that the isolate represents a novel species of the genus Caulobacter, for which the name Caulobacter hibisci sp. nov. is proposed. The type strain is THG-AG3.4T (=KACC 18849T=CCTCC AB 2016077T).

  14. Bowman’s layer transplantation: evidence to date

    Directory of Open Access Journals (Sweden)

    Sharma B

    2018-03-01

    Full Text Available Bhavana Sharma,1 Aditi Dubey,2 Gaurav Prakash,3 Rasik B Vajpayee4–6 1Department of Ophthalmology, All India Institute of Medical Sciences, Bhopal, India; 2Department of Ophthalmology, Gandhi Medical College, Bhopal, India; 3Cornea and Refractive Surgery Services, NMC Eye Care, New Medical Center Specialty Hospital, Abu Dhabi, United Arab Emirates; 4Vision Eye Institute, Melbourne, VIC, Australia; 5Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia; 6North West Academic Centre, University of Melbourne, Melbourne, VIC, Australia Abstract: Surgical management of keratoconus (KC has undergone a paradigm shift in the last two decades and component corneal transplantation technique of deep anterior lamellar keratoplasty has established itself as a modality of choice for management of advanced cases of KC. Every now and then, new minimalist modalities are being innovated for the management of KC. On the same lines, a new technique, Bowman’s layer transplantation, for surgical management of moderate to advanced KC has been reported in recent years. The procedure has shown to be beneficial in reducing ectasia in advanced KC with minimal intraoperative and postoperative complications. In this review, we intend to describe available information and literature with reference to this new surgical technique – Bowman’s layer transplantation. Keywords: keratoconus, Bowman’s Layer, keratoplasty, post PRK haze, component keratoplasty

  15. ORF Alignment: NC_002696 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available ily [imported] - ... Caulobacter crescentus ... Length = 100 ... Query: 213 RIKRFID...DNLCDPELSVGRVAGALGVSPRYVQMVFAGMATTPLAYIXXXXXXXXXXXXXX 272 ... RIKRFIDDNLCDPELSVGRVAGALGV...SPRYVQMVFAGMATTPLAYI ... Sbjct: 1 ... RIKRFIDDNLCDPELSVGRVAGALGVSPRYVQMVFAGMATTPLAYIRRKRLERAARALRE 60 ...

  16. S-layers at second glance? Altiarchaeal grappling hooks (hami resemble archaeal S-layer proteins in structure and sequence

    Directory of Open Access Journals (Sweden)

    Alexandra Kristin Perras

    2015-06-01

    Full Text Available The uncultivated Ca. Altiarchaeum hamiconexum (formerly known as SM1 Euryarchaeon carries highly specialized nano-grappling hooks (hami on its cell surface. Until now little is known about the major protein forming these structured fibrous cell surface appendages, the genes involved or membrane anchoring of these filaments. These aspects were analyzed in depth in this study using environmental transcriptomics combined with imaging methods. Since a laboratory culture of this archaeon is not yet available, natural biofilm samples with high Ca. A. hamiconexum abundance were used for the entire analyses. The filamentous surface appendages spanned both membranes of the cell, which are composed of glycosyl-archaeol. The hami consisted of multiple copies of the same protein, the corresponding gene of which was identified via metagenome-mapped transcriptome analysis. The hamus subunit proteins, which are likely to self-assemble due to their predicted beta sheet topology, revealed no similiarity to known microbial flagella-, archaella-, fimbriae- or pili-proteins, but a high similarity to known S-layer proteins of the archaeal phylum at their N-terminal region (47-44% identity. Our results provide new insights into the structure of the unique hami and their major protein and indicate their divergent evolution with S-layer proteins.

  17. Bacterial S-layer protein coupling to lipids

    DEFF Research Database (Denmark)

    Weygand, M.; Wetzer, B.; Pum, D.

    1999-01-01

    The coupling of bacterial surface (S)-layer proteins to lipid membranes is studied in molecular detail for proteins from Bacillus sphaericus CCM2177 and B. coagulans E38-66 recrystallized at dipalmitoylphosphatidylethanolamine (DPPE) monolayers on aqueous buffer. A comparison of the monolayer...... structure before and after protein recrystallization shows minimal reorganization of the lipid chains. By contrast, the lipid headgroups show major rearrangements. For the B. sphaericus CCM2177 protein underneath DPPE monolayers, x-ray reflectivity data suggest that amino acid side chains intercalate...... the lipid headgroups at least to the phosphate moieties, and probably further beyond. The number of electrons in the headgroup region increases by more than four per lipid. Analysis of the changes of the deduced electron density profiles in terms of a molecular interpretation shows...

  18. ORF Alignment: NC_003551 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available NC_003551 gi|20094874 >1fdr0 4 243 2 220 3e-16 ... ref|NP_421197.1| vanillate O-demet...hylase, reductase subunit [Caulobacter crescentus ... CB15] gb|AAK24365.1| vanillate O-demethylase, r...eductase ... subunit [Caulobacter crescentus CB15] pir||A87546 ... vanillate O-demethylase, re

  19. ORF Alignment: NC_002696 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available NC_002696 gi|16126632 >1rfs0 13 126 17 131 3e-05 ... ref|NP_421196.1| vanillate O-dem...ethylase oxygenase, subunit A [Caulobacter ... crescentus CB15] gb|AAK24364.1| vanillate O-demethylas...e ... oxygenase, subunit A [Caulobacter crescentus CB15] ... pir||H87545 vanillate O-demethyla

  20. ORF Alignment: NC_002696 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available NC_002696 gi|16124962 >1mgtA 4 167 79 239 2e-25 ... ref|NP_419526.1| ada regulatory protein, internal deletion... [Caulobacter crescentus ... CB15] gb|AAK22694.1| ada regulatory protein, internal ... deletio...n [Caulobacter crescentus CB15] pir||B87337 ada ... regulatory protein, internal deletion

  1. ORF Alignment: NC_002696 [GENIUS II[Archive

    Lifescience Database Archive (English)

    Full Text Available NC_002696 gi|16124962 >1adn0 1 76 1 75 1e-17 ... ref|NP_419526.1| ada regulatory protein, internal deletion... [Caulobacter crescentus ... CB15] gb|AAK22694.1| ada regulatory protein, internal ... deletion... [Caulobacter crescentus CB15] pir||B87337 ada ... regulatory protein, internal deletion

  2. The global regulatory architecture of transcription during the Caulobacter cell cycle.

    Directory of Open Access Journals (Sweden)

    Bo Zhou

    2015-01-01

    Full Text Available Each Caulobacter cell cycle involves differentiation and an asymmetric cell division driven by a cyclical regulatory circuit comprised of four transcription factors (TFs and a DNA methyltransferase. Using a modified global 5' RACE protocol, we globally mapped transcription start sites (TSSs at base-pair resolution, measured their transcription levels at multiple times in the cell cycle, and identified their transcription factor binding sites. Out of 2726 TSSs, 586 were shown to be cell cycle-regulated and we identified 529 binding sites for the cell cycle master regulators. Twenty-three percent of the cell cycle-regulated promoters were found to be under the combinatorial control of two or more of the global regulators. Previously unknown features of the core cell cycle circuit were identified, including 107 antisense TSSs which exhibit cell cycle-control, and 241 genes with multiple TSSs whose transcription levels often exhibited different cell cycle timing. Cumulatively, this study uncovered novel new layers of transcriptional regulation mediating the bacterial cell cycle.

  3. Short-Stalked Prosthecomicrobium hirschii Cells Have a Caulobacter-Like Cell Cycle.

    Science.gov (United States)

    Williams, Michelle; Hoffman, Michelle D; Daniel, Jeremy J; Madren, Seth M; Dhroso, Andi; Korkin, Dmitry; Givan, Scott A; Jacobson, Stephen C; Brown, Pamela J B

    2016-02-01

    The dimorphic alphaproteobacterium Prosthecomicrobium hirschii has both short-stalked and long-stalked morphotypes. Notably, these morphologies do not arise from transitions in a cell cycle. Instead, the maternal cell morphology is typically reproduced in daughter cells, which results in microcolonies of a single cell type. In this work, we further characterized the short-stalked cells and found that these cells have a Caulobacter-like life cycle in which cell division leads to the generation of two morphologically distinct daughter cells. Using a microfluidic device and total internal reflection fluorescence (TIRF) microscopy, we observed that motile short-stalked cells attach to a surface by means of a polar adhesin. Cells attached at their poles elongate and ultimately release motile daughter cells. Robust biofilm growth occurs in the microfluidic device, enabling the collection of synchronous motile cells and downstream analysis of cell growth and attachment. Analysis of a draft P. hirschii genome sequence indicates the presence of CtrA-dependent cell cycle regulation. This characterization of P. hirschii will enable future studies on the mechanisms underlying complex morphologies and polymorphic cell cycles. Bacterial cell shape plays a critical role in regulating important behaviors, such as attachment to surfaces, motility, predation, and cellular differentiation; however, most studies on these behaviors focus on bacteria with relatively simple morphologies, such as rods and spheres. Notably, complex morphologies abound throughout the bacteria, with striking examples, such as P. hirschii, found within the stalked Alphaproteobacteria. P. hirschii is an outstanding candidate for studies of complex morphology generation and polymorphic cell cycles. Here, the cell cycle and genome of P. hirschii are characterized. This work sets the stage for future studies of the impact of complex cell shapes on bacterial behaviors. Copyright © 2016, American Society for

  4. S-layer proteins as a source of carotenoids: Isolation of the carotenoid cofactor deinoxanthin from its S-layer protein DR_2577.

    Science.gov (United States)

    Farci, Domenica; Esposito, Francesca; El Alaoui, Sabah; Piano, Dario

    2017-09-01

    S-layers are regular paracrystalline arrays of proteins or glycoproteins that characterize the outer envelope of several bacteria and archaea. The auto-assembling properties of these proteins make them suitable for application in nanotechnologies. However, the bacterial cell wall and its S-layer are also an important binding sites for carotenoids and they may represent a potential source of these precious molecules for industrial purposes. The S-layer structure and its components were extensively studied in the radio-resistant bacterium Deinococcus radiodurans, which for long time represented one of the model organisms in this respect. The protein DR_2577 has been shown to be one of the naturally over-expressed S-layer components in this bacterium. The present report describes a high scale purification procedure of this protein in solution. The purity of the samples, assayed by native and denaturing electrophoresis, showed how this method leads to a selective and high efficient recovery of the pure DR_2577. Recently, we have found that the deinoxanthin, a carotenoid typical of D. radiodurans, is a cofactor non covalently bound to the protein DR_2577. The pure DR_2577 samples may be precipitated or lyophilized and used as a source of the carotenoid cofactor deinoxanthin by an efficient extraction using organic solvents. The procedure described in this work may represent a general approach for the isolation of S-layer proteins and their carotenoids with potentials for industrial applications. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. A study of the thermal denaturation of the S-layer protein from Lactobacillus salivarius

    Science.gov (United States)

    Lighezan, Liliana; Georgieva, Ralitsa; Neagu, Adrian

    2012-09-01

    Surface layer (S-layer) proteins display an intrinsic self-assembly property, forming monomolecular crystalline arrays, identified in outermost structures of the cell envelope in many organisms, such as bacteria and archaea. Isolated S-layer proteins also possess the ability to recrystallize into regular lattices, being used in biotechnological applications, such as controlling the architecture of biomimetic surfaces. To this end, the stability of the S-layer proteins under high-temperature conditions is very important. In this study, the S-layer protein has been isolated from Lactobacillus salivarius 16 strain of human origin, and purified by cation-exchange chromatography. Using circular dichroism (CD) spectroscopy, we have investigated the thermal denaturation of the S-layer protein. The far- and near-UV CD spectra have been collected, and the temperature dependence of the CD signal in these spectral domains has been analyzed. The variable temperature results show that the secondary and tertiary structures of the S-layer protein change irreversibly due to the heating of the sample. After the cooling of the heated protein, the secondary and tertiary structures are partially recovered. The denaturation curves show that the protein unfolding depends on the sample concentration and on the heating rate. The secondary and tertiary structures of the protein suffer changes in the same temperature range. We have also detected an intermediate state in the protein denaturation pathway. Our results on the thermal behavior of the S-layer protein may be important for the use of S-layer proteins in biotechnological applications, as well as for a better understanding of the structure and function of S-layer proteins.

  6. Phylogeny by a polyphasic approach of the order Caulobacterales, proposal of Caulobacter mirabilis sp. nov., Phenylobacterium haematophilum sp. nov. and Phenylobacterium conjunctum sp. nov., and emendation of the genus Phenylobacterium.

    Science.gov (United States)

    Abraham, Wolf-Rainer; Macedo, Alexandre J; Lünsdorf, Heinrich; Fischer, Roman; Pawelczyk, Sonja; Smit, John; Vancanneyt, Marc

    2008-08-01

    Three strains of Gram-negative, rod-shaped, non-spore-forming bacteria were isolated from fresh water and human blood. As determined by analyses of 16S rRNA gene sequences, the prosthecate strain FWC 38T was affiliated to the alphaproteobacterial genus Caulobacter, with Caulobacter henricii (96.8 %) and Caulobacter fusiformis (96.8 %) as its closest relatives. The non-prosthecate strain LMG 11050T and the prosthecate strain FWC 21T both belonged to the genus Phenylobacterium with Phenylobacterium koreense (96.9 %) and Phenylobacterium immobile (96.3 %) as the closest relatives. This affiliation was supported by chemotaxonomic data (polar lipids and cellular fatty acids). Physiological and biochemical tests allowed genotypic and phenotypic differentiation of the novel strains from all hitherto recognized species of the genera Caulobacter and Phenylobacterium. The strains therefore represent novel species, for which the names Caulobacter mirabilis sp. nov. (type strain FWC 38T=LMG 24261T=CCUG 55073T), Phenylobacterium conjunctum (type strain FWC 21T=LMG 24262T=CCUG 55074T), the first described prosthecate Phenylobacterium species, and Phenylobacterium haematophilum sp. nov. (type strain LMG 11050T=CCUG 26751T) are proposed. Marker nucleotides within the 16S rRNA genes were determined for the genera Asticcacaulis, Brevundimonas, Caulobacter and Phenylobacterium and the description of the genus Phenylobacterium is emended.

  7. The S-Layer Glycome—Adding to the Sugar Coat of Bacteria

    Directory of Open Access Journals (Sweden)

    Robin Ristl

    2011-01-01

    Full Text Available The amazing repertoire of glycoconjugates present on bacterial cell surfaces includes lipopolysaccharides, capsular polysaccharides, lipooligosaccharides, exopolysaccharides, and glycoproteins. While the former are constituents of Gram-negative cells, we review here the cell surface S-layer glycoproteins of Gram-positive bacteria. S-layer glycoproteins have the unique feature of self-assembling into 2D lattices providing a display matrix for glycans with periodicity at the nanometer scale. Typically, bacterial S-layer glycans are O-glycosidically linked to serine, threonine, or tyrosine residues, and they rely on a much wider variety of constituents, glycosidic linkage types, and structures than their eukaryotic counterparts. As the S-layer glycome of several bacteria is unravelling, a picture of how S-layer glycoproteins are biosynthesized is evolving. X-ray crystallography experiments allowed first insights into the catalysis mechanism of selected enzymes. In the future, it will be exciting to fully exploit the S-layer glycome for glycoengineering purposes and to link it to the bacterial interactome.

  8. Biomimetic interfaces based on S-layer proteins, lipid membranes and functional biomolecules

    Science.gov (United States)

    Schuster, Bernhard; Sleytr, Uwe B.

    2014-01-01

    Designing and utilization of biomimetic membrane systems generated by bottom-up processes is a rapidly growing scientific and engineering field. Elucidation of the supramolecular construction principle of archaeal cell envelopes composed of S-layer stabilized lipid membranes led to new strategies for generating highly stable functional lipid membranes at meso- and macroscopic scale. In this review, we provide a state-of-the-art survey of how S-layer proteins, lipids and polymers may be used as basic building blocks for the assembly of S-layer-supported lipid membranes. These biomimetic membrane systems are distinguished by a nanopatterned fluidity, enhanced stability and longevity and, thus, provide a dedicated reconstitution matrix for membrane-active peptides and transmembrane proteins. Exciting areas in the (lab-on-a-) biochip technology are combining composite S-layer membrane systems involving specific membrane functions with the silicon world. Thus, it might become possible to create artificial noses or tongues, where many receptor proteins have to be exposed and read out simultaneously. Moreover, S-layer-coated liposomes and emulsomes copying virus envelopes constitute promising nanoformulations for the production of novel targeting, delivery, encapsulation and imaging systems. PMID:24812051

  9. An optimized multilayer structure of CdS layer for CdTe solar cells application

    International Nuclear Information System (INIS)

    Han Junfeng; Liao Cheng; Jiang Tao; Spanheimer, C.; Haindl, G.; Fu, Ganhua; Krishnakumar, V.; Zhao Kui; Klein, A.; Jaegermann, W.

    2011-01-01

    Research highlights: → Two different methods to prepare CdS films for CdTe solar cells. → A new multilayer structure of window layer for the CdTe solar cell. → Thinner CdS window layer for the solar cell than the standard CdS layer. → Higher performance of solar cells based on the new multilayer structure. - Abstract: CdS layers grown by 'dry' (close space sublimation) and 'wet' (chemical bath deposition) methods are deposited and analyzed. CdS prepared with close space sublimation (CSS) has better crystal quality, electrical and optical properties than that prepared with chemical bath deposition (CBD). The performance of CdTe solar cell based on the CSS CdS layer has higher efficiency than that based on CBD CdS layer. However, the CSS CdS suffers from the pinholes. And consequently it is necessary to prepare a 150 nm thin film for CdTe/CdS solar cell. To improve the performance of CdS/CdTe solar cells, a thin multilayer structure of CdS layer (∼80 nm) is applied, which is composed of a bottom layer (CSS CdS) and a top layer (CBD CdS). That bi-layer film can allow more photons to pass through it and significantly improve the short circuit current of the CdS/CdTe solar cells.

  10. Structural analysis and evidence for dynamic emergence of Bacillus anthracis S-layer networks.

    Science.gov (United States)

    Couture-Tosi, Evelyne; Delacroix, Hervé; Mignot, Tâm; Mesnage, Stéphane; Chami, Mohamed; Fouet, Agnès; Mosser, Gervaise

    2002-12-01

    Surface layers (S-layers), which form the outermost layers of many Bacteria and Archaea, consist of protein molecules arranged in two-dimensional crystalline arrays. Bacillus anthracis, a gram-positive, spore-forming bacterium, responsible for anthrax, synthesizes two abundant surface proteins: Sap and EA1. Regulatory studies showed that EA1 and Sap appear sequentially at the surface of the parental strain. Sap and EA1 can form arrays. The structural parameters of S-layers from mutant strains (EA1(-) and Sap(-)) were determined by computer image processing of electron micrographs of negatively stained regular S-layer fragments or deflated whole bacteria. Sap and EA1 projection maps were calculated on a p1 symmetry basis. The unit cell parameters of EA1 were a = 69 A, b = 83 A, and gamma = 106 degrees, while those of Sap were a = 184 A, b = 81 A, and gamma = 84 degrees. Freeze-etching experiments and the analysis of the peripheral regions of the cell suggested that the two S-layers have different settings. We characterized the settings of each network at different growth phases. Our data indicated that the scattered emergence of EA1 destabilizes the Sap S-layer.

  11. Metal ion-specific thermal stability of bacterial S-Layers

    Energy Technology Data Exchange (ETDEWEB)

    Drobot, Bjoern; Raff, Johannes [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Biogeochemistry; Fahmy, Karim [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Biophysics

    2016-07-01

    Many bacteria are covered by a surface layer (S-layer), i.e., a para-crystalline two-dimensional array of proteins which control cell shape, act as molecular sieves and have potential applications as radionuclide-binding material for bioremediation of polluted areas. Knowledge and control of the metal-dependent stability of the purified proteins is required for their technical application. Here, we have explored by differential scanning calorimetry the thermal stability of the S-layer protein slp-B53 from Lysinibacillus sphaericus, a Gram-positive bacterium isolated from a uranium mining waste pile [1].

  12. FTIR spectroscopy structural analysis of the interaction between Lactobacillus kefir S-layers and metal ions

    Science.gov (United States)

    Gerbino, E.; Mobili, P.; Tymczyszyn, E.; Fausto, R.; Gómez-Zavaglia, A.

    2011-02-01

    FTIR spectroscopy was used to structurally characterize the interaction of S-layer proteins extracted from two strains of Lactobacillus kefir (the aggregating CIDCA 8348 and the non-aggregating JCM 5818) with metal ions (Cd +2, Zn +2, Pb +2 and Ni +2). The infrared spectra indicate that the metal/protein interaction occurs mainly through the carboxylate groups of the side chains of Asp and Glut residues, with some contribution of the NH groups belonging to the peptide backbone. The frequency separation between the νCOO - anti-symmetric and symmetric stretching vibrations in the spectra of the S-layers in presence of the metal ions was found to be ca. 190 cm -1 for S-layer CIDCA 8348 and ca. 170 cm -1 for JCM 5818, denoting an unidentate coordination in both cases. Changes in the secondary structures of the S-layers induced by the interaction with the metal ions were also noticed: a general trend to increase the amount of β-sheet structures and to reduce the amount of α-helices was observed. These changes allow the proteins to adjust their structure to the presence of the metal ions at minimum energy expense, and accordingly, these adjustments were found to be more important for the bigger ions.

  13. Expression, secretion and antigenic variation of bacterial S-layer proteins

    NARCIS (Netherlands)

    Boot, H.J.; Pouwels, P.H.

    1996-01-01

    The function of the S-layer, a regularly arranged structure on the outside of numerous bacteria, appears to be different for bacteria living in different environments. Almost no similarity exists between the primary sequences of S-proteins, although their amino acid composition is comparable.

  14. The S-layer gene of Lactobacillus helveticus CNRZ 892 : cloning, sequence and heterologous expression

    NARCIS (Netherlands)

    Callegari, M.L.; Riboli, B.; Sanders, J.W; Cocconcelli, P.S.; Kok, J.; Venema, G; Morelli, L.

    1998-01-01

    Lactobacillus helveticus CNRZ 892 contains a surface layer (S-layer) composed of protein monomers of 43 kDa organized in regular arrays. The gene encoding this protein (slpH) has been cloned in Escherichia coli and sequenced. slpH consists of 440 codons and is preceded by a ribosome-binding site

  15. Characterization of the Collagen-Binding S-Layer Protein CbsA of Lactobacillus crispatus

    Science.gov (United States)

    Sillanpää, Jouko; Martínez, Beatriz; Antikainen, Jenni; Toba, Takahiro; Kalkkinen, Nisse; Tankka, Sanna; Lounatmaa, Kari; Keränen, Jaakko; Höök, Magnus; Westerlund-Wikström, Benita; Pouwels, Peter H.; Korhonen, Timo K.

    2000-01-01

    The cbsA gene of Lactobacillus crispatus strain JCM 5810, encoding a protein that mediates adhesiveness to collagens, was characterized and expressed in Escherichia coli. The cbsA open reading frame encoded a signal sequence of 30 amino acids and a mature polypeptide of 410 amino acids with typical features of a bacterial S-layer protein. The cbsA gene product was expressed as a His tag fusion protein, purified by affinity chromatography, and shown to bind solubilized as well as immobilized type I and IV collagens. Three other Lactobacillus S-layer proteins, SlpA, CbsB, and SlpnB, bound collagens only weakly, and sequence comparisons of CbsA with these S-layer proteins were used to select sites in cbsA where deletions and mutations were introduced. In addition, hybrid S-layer proteins that contained the N or the C terminus from CbsA, SlpA, or SlpnB as well as N- and C-terminally truncated peptides from CbsA were constructed by gene fusion. Analysis of these molecules revealed the major collagen-binding region within the N-terminal 287 residues and a weaker type I collagen-binding region in the C terminus of the CbsA molecule. The mutated or hybrid CbsA molecules and peptides that failed to polymerize into a periodic S-layer did not bind collagens, suggesting that the crystal structure with a regular array is optimal for expression of collagen binding by CbsA. Strain JCM 5810 was found to contain another S-layer gene termed cbsB that was 44% identical in sequence to cbsA. RNA analysis showed that cbsA, but not cbsB, was transcribed under laboratory conditions. S-layer-protein-expressing cells of strain JCM 5810 adhered to collagen-containing regions in the chicken colon, suggesting that CbsA-mediated collagen binding represents a true tissue adherence property of L. crispatus. PMID:11053389

  16. A Bacillus thuringiensis S-Layer Protein Involved in Toxicity against Epilachna varivestis (Coleoptera: Coccinellidae)

    Science.gov (United States)

    Peña, Guadalupe; Miranda-Rios, Juan; de la Riva, Gustavo; Pardo-López, Liliana; Soberón, Mario; Bravo, Alejandra

    2006-01-01

    The use of Bacillus thuringiensis as a biopesticide is a viable alternative for insect control since the insecticidal Cry proteins produced by these bacteria are highly specific; harmless to humans, vertebrates, and plants; and completely biodegradable. In addition to Cry proteins, B. thuringiensis produces a number of extracellular compounds, including S-layer proteins (SLP), that contribute to virulence. The S layer is an ordered structure representing a proteinaceous paracrystalline array which completely covers the surfaces of many pathogenic bacteria. In this work, we report the identification of an S-layer protein by the screening of B. thuringiensis strains for activity against the coleopteran pest Epilachna varivestis (Mexican bean beetle; Coleoptera: Coccinellidae). We screened two B. thuringiensis strain collections containing unidentified Cry proteins and also strains isolated from dead insects. Some of the B. thuringiensis strains assayed against E. varivestis showed moderate toxicity. However, a B. thuringiensis strain (GP1) that was isolated from a dead insect showed a remarkably high insecticidal activity. The parasporal crystal produced by the GP1 strain was purified and shown to have insecticidal activity against E. varivestis but not against the lepidopteran Manduca sexta or Spodoptera frugiperda or against the dipteran Aedes aegypti. The gene encoding this protein was cloned and sequenced. It corresponded to an S-layer protein highly similar to previously described SLP in Bacillus anthracis (EA1) and Bacillus licheniformis (OlpA). The phylogenetic relationships among SLP from different bacteria showed that these proteins from Bacillus cereus, Bacillus sphaericus, B. anthracis, B. licheniformis, and B. thuringiensis are arranged in the same main group, suggesting similar origins. This is the first report that demonstrates that an S-layer protein is directly involved in toxicity to a coleopteran pest. PMID:16391064

  17. Bowman’s layer encystment in cases of persistent Acanthamoeba keratitis

    Directory of Open Access Journals (Sweden)

    Yokogawa H

    2012-08-01

    Full Text Available Hideaki Yokogawa,1 Akira Kobayashi,1 Natsuko Yamazaki,1 Yasuhisa Ishibashi,2 Yosaburo Oikawa,3 Masaharu Tokoro,4 Kazuhisa Sugiyama11Department of Ophthalmology, Kanazawa University Graduate School of Medical Science, Kanazawa, 2Department of Ophthalmology, East Washinomiya Hospital, Kuki, 3Department of Medical Zoology, Kanazawa Medical University, Kahoku, 4Department of Parasitology, Kanazawa University Graduate School of Medical Science, Kanazawa, JapanBackground: The purpose of this study was to report Acanthamoeba encystment in Bowman’s layer in Japanese cases of persistent Acanthamoeba keratitis (AK.Methods: Laser confocal microscopic images of the cornea were obtained in vivo from 18 consecutive eyes from 17 confirmed AK patients. Retrospectively, 14 cases treated over 4 months were categorized as a nonpersistent group and three cases that required prolonged therapy for more than 6 months were categorized as a persistent group. Clinical outcomes based on final best-corrected visual acuity were retrospectively analyzed, and selected confocal images were evaluated qualitatively for abnormal findings.Results: The final best-corrected visual acuity was significantly lower (P < 0.01 for patients in the persistent group compared with that in the nonpersistent group. At the initial visit, in vivo confocal microscopy demonstrated Acanthamoeba cysts exclusively in the epithelial layer in both the nonpersistent group (80% and the persistent group (100%. At a subsequent follow-up visit, numerous Acanthamoeba cysts were observed in the epithelial cell layer and in Bowman’s layer in all patients with persistent AK, but Acanthamoeba cysts were undetectable in all cases with nonpersistent AK tested.Conclusion: Invasion of cysts into Bowman’s layer was characteristically observed in patients with persistence of AK. This finding suggests that invasion of Acanthamoeba cysts into Bowman’s layer may be a useful predictor for a persistent clinical

  18. Photoconductive Phenomenon Observed from ZnS Layer Deposition for a Potential of IR Sensor Applications

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    Hariyadi SOETEDJO

    2010-12-01

    Full Text Available Photoconductive phenomenon has been observed from the ZnS layer deposition on the quartz substrate. Determination of film thickness of materials has been done through the fitting procedure of optical transmittance obtained from the measurement in visible-NIR (near infrared spectral region. The optical transmittance of ZnS layer has been observed to have more oscillating from 50 to 70 % over the spectrum for thicker layer of 290 nm. These results show an encouraging work of layer thickness determination for some IR materials through a visible-NIR spectral region. The photoconductive phenomenon has been observed for a variation of temperatures introduced to the sample from 30 to 42 °C. The increase of temperature was followed by the increase of output voltage that indicates the increase of current flow due to the photoconductive phenomenon.

  19. Monodisperse gold nanoparticles formed on bacterial crystalline surface layers (S-layers) by electroless deposition

    Energy Technology Data Exchange (ETDEWEB)

    Dieluweit, S. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Pum, D. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Sleytr, U.B. [Center for Nanobiotechnology, University of Natural Resources and Applied Life Sciences (BOKU), Gregor Mendel-Strasse 33, A-1180 Vienna (Austria); Kautek, W. [Department for Physical Chemistry, University of Vienna, Waehringer Strasse 42, A-1090 Vienna (Austria)]. E-mail: wolfgang.kautek@univie.ac.at

    2005-12-15

    The fabrication of patterned arrays of nanoparticles whose electronic, optical and magnetic properties will find technological applications, such as ultra-high-density memories, is currently one of the most important objectives of inorganic material research. In this study, the in situ electroless nucleation of ordered two-dimensional arrays of gold nanoparticles (5 nm in size) by using bacterial S-layers as molecular templates and their characterization by small spot X-ray photoelectron emission spectroscopy (XPS) is presented. This yielded the elemental composition of the nanoclusters, which consisted of almost entirely elemental gold, and possible side reactions on the cluster and protein surface. The preferential deposition of the gold nanoparticles on the S-layer suggests that topography and functional groups are important for superlattice formation.

  20. Synthesis and Characterization of Ag2S Layers Formed on Polypropylene

    Directory of Open Access Journals (Sweden)

    Valentina Krylova

    2013-01-01

    Full Text Available Silver sulphide, Ag2S, layers on the surface of polypropylene (PP film was formed by chemical bath deposition method (CBD. Film samples were characterised by X-ray photoelectron spectroscopy (XPS, attenuated total reflection Fourier transform infrared (ATR-FTIR spectroscopy, scanning electron microscopy (SEM, atomic force microscopy (AFM, and X-ray diffraction analysis (XRD. The surface morphology, texture, and uniformity of the silver sulphide layers were formed on PP surface dependent on the number of polymer immersions in the precursor solution. XPS analysis confirmed that on the surface of the polypropylene film, a layer of Ag2S was formed. ATR-FTIR and FTIR spectra analysis showed that the surface of Ag2S layers is slightly oxidized. All prepared layers gave multiple XRD reflections, corresponding to monoclinic Ag2S (acanthite. The Ag2S layer on polypropylene was characterized as an Ag+ ion selective electrode in terms of potential response and detection limit. The electrode was also tested as an end-point electrode for argentometric titration of thiamine hydrochloride.

  1. Surface-Layer (S-Layer) Proteins Sap and EA1 Govern the Binding of the S-Layer-Associated Protein BslO at the Cell Septa of Bacillus anthracis

    Science.gov (United States)

    Kern, Valerie J.; Kern, Justin W.; Theriot, Julie A.; Schneewind, Olaf

    2012-01-01

    The Gram-positive pathogen Bacillus anthracis contains 24 genes whose products harbor the structurally conserved surface-layer (S-layer) homology (SLH) domain. Proteins endowed with the SLH domain associate with the secondary cell wall polysaccharide (SCWP) following secretion. Two such proteins, Sap and EA1, have the unique ability to self-assemble into a paracrystalline layer on the surface of bacilli and form S layers. Other SLH domain proteins can also be found within the S layer and have been designated Bacillus S-layer-associated protein (BSLs). While both S-layer proteins and BSLs bind the same SCWP, their deposition on the cell surface is not random. For example, BslO is targeted to septal peptidoglycan zones, where it catalyzes the separation of daughter cells. Here we show that an insertional lesion in the sap structural gene results in elongated chains of bacilli, as observed with a bslO mutant. The chain length of the sap mutant can be reduced by the addition of purified BslO in the culture medium. This complementation in trans can be explained by an increased deposition of BslO onto the surface of sap mutant bacilli that extends beyond chain septa. Using fluorescence microscopy, we observed that the Sap S layer does not overlap the EA1 S layer and slowly yields to the EA1 S layer in a growth-phase-dependent manner. Although present all over bacilli, Sap S-layer patches are not observed at septa. Thus, we propose that the dynamic Sap/EA1 S-layer coverage of the envelope restricts the deposition of BslO to the SCWP at septal rings. PMID:22609927

  2. Expression and cytosolic assembly of the S-layer fusion protein mSbsC-EGFP in eukaryotic cells

    NARCIS (Netherlands)

    Blecha, Andreas; Zarschler, Kristof; Sjollema, Klaas A.; Veenhuis, Marten; Rödel, Gerhard; Rodel, G.

    2005-01-01

    Background: Native as well as recombinant bacterial cell surface layer (S-layer) protein of Geobacillus (G.) stearothermophilus ATCC 12980 assembles to supramolecular structures with an oblique symmetry. Upon expression in E. coli, S-layer self assembly products are formed in the cytosol. We tested

  3. Rapid fluctuations in the northern Baltic Sea H2S layer

    Science.gov (United States)

    Kankaanpää, Harri T.; Virtasalo, Joonas J.

    2017-12-01

    Hydrogen sulfide (H2S) is linked to water quality deterioration in the Baltic Sea, with widespread seafloor hypoxia. We examined the vertical and temporal variability of in situ [H2S], oxygen concentration ([O2]), temperature (T) and pH at weekly, hourly and minute intervals at 13 locations in the western Gulf of Finland in 2013-2014. The main target was the 60-100 m water depth range, containing 3.2-290 μM O2 and 6.3-22.6 μM H2S. Where gas was detected by acoustic surveys, the structure of the H2S layer was more complex compared to stations devoid of gas. Local minima and maxima in pH frequently occurred near the H2S upper boundary (redox transition zone). Except for the homogeneous, tranquil zone above the seafloor at some stations, substantial rapid changes in hydrographic conditions were common. Typically, a layer of marked temporal T variability was present atop or within the topmost H2S layers. The largest temporal changes over a weekly period were - 0.44 °C/- 10.8 μM H2S/- 0.12 pH units (at seafloor level), + 0.18 °C/+7.9 μM H2S between casts (1 h) and + 0.03 °C/- 2.5 μM H2S per minute (high resolution logging). Abrupt [H2S] changes were recorded at two stations with sediments containing free gas. The T and [H2S] changes were synchronous at several layers, reflecting water movement. We conclude that rapid changes occur in hydrographic conditions in the near-bottom H2S layer in the northern Baltic Sea, especially at locations where free gas is present in the underlying sediments.

  4. Preparation and Characterization of TiO2/CdS Layers as Potential Photoelectrocatalytic Materials

    Directory of Open Access Journals (Sweden)

    Teofil-Danut Silipas

    2011-01-01

    Full Text Available The TiO2/CdS semiconductor composites were prepared on
    indium tin oxide (ITO substrates in di®erent mass proportions via wet-chemical techniques using bi-distilled water, acetyl-acetone, poly-propylene-glycol and Triton X-100 as additives. The composite layers were annealed in normal conditions at the temperature of 450±C, 120 min. with a rate of temperature increasing of 5±C/min. The structural and optical properties of all the TiO2/CdS ayers were characterized by X-ray di®raction, UV-VIS spectroscopy, spectrofluorimetry and FT/IR microscopy. The microstructural properties of the deposited TiO2/CdS layers can be modi¯ed by varying the mass proportions of TiO2:CdS. The good crystallinity level and the high optical adsorption of
    the TiO2/CdS layers make them attractive for photoelectrochemical cell applications.

  5. S-Layer Glycoproteins and Flagellins: Reporters of Archaeal Posttranslational Modifications

    Directory of Open Access Journals (Sweden)

    Ken F. Jarrell

    2010-01-01

    Full Text Available Many archaeal proteins undergo posttranslational modifications. S-layer proteins and flagellins have been used successfully to study a variety of these modifications, including N-linked glycosylation, signal peptide removal and lipid modification. Use of these well-characterized reporter proteins in the genetically tractable model organisms, Haloferax volcanii, Methanococcus voltae and Methanococcus maripaludis, has allowed dissection of the pathways and characterization of many of the enzymes responsible for these modifications. Such studies have identified archaeal-specific variations in signal peptidase activity not found in the other domains of life, as well as the enzymes responsible for assembly and biosynthesis of novel N-linked glycans. In vitro assays for some of these enzymes have already been developed. N-linked glycosylation is not essential for either Hfx. volcanii or the Methanococcus species, an observation that allowed researchers to analyze the role played by glycosylation in the function of both S-layers and flagellins, by generating mutants possessing these reporters with only partial attached glycans or lacking glycan altogether. In future studies, it will be possible to consider questions related to the heterogeneity associated with given modifications, such as differential or modulated glycosylation.

  6. Langmuir–Blodgett films of cholesterol oxidase and S-layer proteins onto screen-printed electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Guimarães, Juliana Aguilar, E-mail: helen@peq.coppe.ufrj.br; Ferraz, Helen Conceição; Alves, Tito Lívio Moitinho

    2014-04-01

    Graphical abstract: - Highlights: • Langmuir and LB monolayers of ChOx and S-layer proteins were obtained. • Mixed ChOx/S-layer proteins films presented an ideal-like behavior. • Modified sensor showed stable peaks with moderate intensity. • The type of LB deposition affects the sensor ability of detecting cholesterol. • Mixed ChOx/S-layer proteins LB films improve sensor properties. - Abstract: Stable Langmuir monolayers of cholesterol oxidase (ChOx) and S-layer proteins were produced at the water–air interface and subsequently transferred onto the surface of screen-printed carbon electrodes by the Langmuir–Blodgett (LB) technique. The modified electrode surface was characterized by atomic force microscopy (AFM) and cyclic voltammetry (CV). AFM indicated the presence of deposited layers, showing reduction of surface roughness (RMS and Rt parameters). Significant changes in the shape of CVs were observed in modified electrodes compared to bare electrodes. The anodic peaks could be observed in cyclic voltammograms (CV), at a scan rate equal to 25 mV s{sup −1}, using electrodes with Z-type LB deposition. The presence of S-layer proteins in the ChOx LB film increases the oxidation peak intensity and reduces the oxidation potential. Altogether, these results demonstrate the feasibility of producing a cholesterol biosensor based on the immobilization of ChOx and S-layer proteins by LB technique.

  7. S-layer proteins from Lactobacillus sp. inhibit bacterial infection by blockage of DC-SIGN cell receptor.

    Science.gov (United States)

    Prado Acosta, Mariano; Ruzal, Sandra M; Cordo, Sandra M

    2016-11-01

    Many species of Lactobacillus sp. possess Surface(s) layer proteins in their envelope. Among other important characteristics S-layer from Lactobacillus acidophilus binds to the cellular receptor DC-SIGN (Dendritic Cell-Specific Intercellular adhesion molecule-3-Grabbing Non-integrin; CD209), which is involved in adhesion and infection of several families of bacteria. In this report we investigate the activity of new S-layer proteins from the Lactobacillus family (Lactobacillus acidophilus, Lactobacillus brevis, Lactobacillus helveticus and Lactobacillus kefiri) over the infection of representative microorganisms important to human health. After the treatment of DC-SIGN expressing cells with these proteins, we were able to diminish bacterial infection by up to 79% in both gram negative and mycobacterial models. We discovered that pre-treatment of the bacteria with S-layers from Lactobacillus acidophilus and Lactobacillus brevis reduced bacteria viability but also prevent infection by the pathogenic bacteria. We also proved the importance of the glycosylation of the S-layer from Lactobacillus kefiri in the binding to the receptor and thus inhibition of infection. This novel characteristic of the S-layers proteins may contribute to the already reported pathogen exclusion activity for these Lactobacillus probiotic strains; and might be also considered as a novel enzymatic antimicrobial agents to inhibit bacterial infection and entry to host cells. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. S-Layered Aneurinibacillus and Bacillus spp. Are Susceptible to the Lytic Action of Pseudomonas aeruginosa Membrane Vesicles

    Science.gov (United States)

    Kadurugamuwa, J. L.; Mayer, A.; Messner, P.; Sára, M.; Sleytr, U. B.; Beveridge, T. J.

    1998-01-01

    When S-layered strains of Bacillus stearothermophilus and Aneurinibacillus thermoaerophilus, possessing S-layers of different lattice type and lattice constant as well as S-(glyco)protein chemistry, and isogenic S-layerless variants were subjected to membrane vesicles (MVs) from P. aeruginosa during plaque assays on plates or CFU measurements on cell suspensions, all bacterial types lysed. Electron microscopy of negative stains, thin sections, and immunogold-labelled MV preparations revealed that the vesicles adhered to all bacterial surfaces, broke open, and digested the underlying peptidoglycan-containing cell wall of all cell types. Reassembled S-layer did not appear to be affected by MVs, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis showed that the S-(glyco)proteins remained intact. meso-Diaminopimelic acid, as a peptidoglycan breakdown product, was found in all culture supernatants after MV attack. These results suggest that even though MVs are much larger than the channels which penetrate these proteinaceous arrays, S-layers on gram-positive bacteria do not form a defensive barrier against the lytic action of MVs. The primary mode of attack is by the liberation from the MVs of a peptidoglycan hydrolase, which penetrates through the S-layer to digest the underlying peptidoglycan-containing cell wall. The S-layer is not affected by MV protease. PMID:9573179

  9. In Vitro Characterization of the Two-Stage Non-Classical Reassembly Pathway of S-Layers

    Directory of Open Access Journals (Sweden)

    Andreas Breitwieser

    2017-02-01

    Full Text Available The recombinant bacterial surface layer (S-layer protein rSbpA of Lysinibacillus sphaericus CCM 2177 is an ideal model system to study non-classical nucleation and growth of protein crystals at surfaces since the recrystallization process may be separated into two distinct steps: (i adsorption of S-layer protein monomers on silicon surfaces is completed within 5 min and the amount of bound S-layer protein sufficient for the subsequent formation of a closed crystalline monolayer; (ii the recrystallization process is triggered—after washing away the unbound S-layer protein—by the addition of a CaCl2 containing buffer solution, and completed after approximately 2 h. The entire self-assembly process including the formation of amorphous clusters, the subsequent transformation into crystalline monomolecular arrays, and finally crystal growth into extended lattices was investigated by quartz crystal microbalance with dissipation (QCM-D and atomic force microscopy (AFM. Moreover, contact angle measurements showed that the surface properties of S-layers change from hydrophilic to hydrophobic as the crystallization proceeds. This two-step approach is new in basic and application driven S-layer research and, most likely, will have advantages for functionalizing surfaces (e.g., by spray-coating with tailor-made biological sensing layers.

  10. Crystalline Bacterial Surface Layer (S-Layer) Opens Golden Opportunities for Nanobiotechnology in Textiles.

    Science.gov (United States)

    Asadi, Narges; Chand, Nima; Rassa, Mehdi

    2015-12-01

    This study focuses on the successful recrystallization of bacterial S-layer arrays of the Lactobacillus acidophilus ATCC 4356 at textile surfaces to create a novel method and material. Optimum bacterial growth was obtained at approximately 45 °C, pH 5.0, and 14 h pi. The cells were resuspended in guanidine hydrochloride and the 43 kDa S-protein was dialyzed and purified. The optimum reassembly on the polypropylene fabric surface in terms of scanning electron microscopy (SEM), reflectance, and uniformity (spectrophotometry) was obtained at 30 °C, pH 5.0 for 30 minutes in the presence of 2 gr/l (liquor ratio; 1:40) of the S-protein. Overall, our data showed that the functional aspects and specialty applications of the fabric would be very attractive for the textile and related sciences, and result in advanced technical textiles.

  11. Formation of CuxS Layers on Polypropylene Sulfurized by Molten Sulfur

    Directory of Open Access Journals (Sweden)

    Rasa ALABURDAITĖ

    2011-11-01

    Full Text Available The processes of formation of electrically conductive layers of copper sulfides CuxS by the sorption-diffusion method on polypropylene (PP using molten sulfur as sulfurizing agent was investigated. The amount of sorbed sulfur increased with the increase of the duration of treatment. Copper sulfide layers were formed on the surface of polypropylene after the treatment of sulfurized polymer with Cu(II/I salt solution. The amount of copper sulfide in layer increased with the increase of treatment duration in copper salt solution. XRD spectra of PP films treated for 3 min with molten sulfur and then with Cu(II/I salt solution for the different time showed that the copper sulfide phases, mostly digenite, Cu2-xS and a-chalcocite, Cu2S were formed in the layers. Electromotive force measurement results confirmed the composition of formed CuxS layers on PP. The phase composition of layers also changed after the annealing. The value of electrical resistance of copper sulfide layers on PP varied from 20 W/cm2 to 80 W/cm2 and after annealing at 80 °C - in the interval of 10 W/cm2 - 60 W/cm2.http://dx.doi.org/10.5755/j01.ms.17.4.776

  12. Coexisting properties of thermostability and ultraviolet radiation resistance in the main S-layer complex of Deinococcus radiodurans.

    Science.gov (United States)

    Farci, Domenica; Slavov, Chavdar; Piano, Dario

    2018-01-17

    Deinococcus radiodurans is well known for its unusual resistance to different environmental stresses. Recently, we have described a novel complex composed of the surface (S)-layer protein DR_2577 and the carotenoid deinoxanthin. We also showed a role of this complex in the UV resistance under desiccation. Both these properties, UV and desiccation resistance, suggest a selective pressure generated by Sun irradiation. In order to confirm this hypothesis we checked whether this S-layer Deinoxanthin Binding Complex (SDBC) has features of thermo-resistance, a property also expected in proteins evolved under solar irradiative pressure. We performed the spectroscopic characterization of the SDBC by means of thermal shift assay, circular dichroism and related in silico analysis. Our findings identify a stability typical of thermo-adapted proteins and provide a new insight into the origin of specific S-layer types. The results are discussed in terms of co-evolutionary mechanisms related to Sun-induced desiccation and heat.

  13. Effects of ZnS layer on the performance improvement of the photosensitive ZnO nanowire arrays solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Javed, Hafiz Muhammad Asif [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Que, Wenxiu, E-mail: wxque@mail.xjtu.edu.cn [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Gao, Yanping; Xing, Yonglei [Electronic Materials Research Laboratory, International Center for Dielectric Research, Key Laboratory of the Ministry of Education, Xi' an Jiaotong University, Xi' an, 710049 (China); Kong, Ling Bing, E-mail: ELBKong@ntu.edu.sg [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue, 639798 (Singapore)

    2016-08-01

    The impact of ZnS layer as an interface modification on the photosensitive ZnO nanowire arrays solar cells was studied. CdS, CdSe and ZnS were deposited on ZnO nanowire arrays by SILAR method. When a ZnS layer was deposited, the quantum dot barrier was indirectly become in contact with the electrolyte, which thus restrained the flow of electrons. The CdS sensitized solar cells has an efficiency of 0.55% with the deposition of the ZnS(3) layer, that is, with a deposition of three times, whereas the CdS/CdSe co-sensitized solar cells has an efficiency of 2.03% with the deposition of the ZnS(1) layer. It was also noted that as the thickness of the of ZnS layer was increased, V{sub oc}, I{sub sc} and efficiencies of both the solar cells were first increased and then decreased. In addition, the CdS/N719 solar cells has an efficiency of 0.75% with the deposition of the ZnS(2) layer. - Highlights: • The impact of ZnS layer on the photosensitive ZnO nanowire solar cells was studied. • ZnS layer restrained the flow of electrons to the electrolyte. • CdS/CdSe co-sensitized solar cells have higher efficiency than CdS solar cells. • When ZnS layer was increased, V{sub oc} and I{sub sc} firstly increased and then decreased.

  14. Role of S-layer proteins in the biosorption capacity of lead by Lactobacillus kefir.

    Science.gov (United States)

    Gerbino, Esteban; Carasi, Paula; Araujo-Andrade, Cuauhtémoc; Tymczyszyn, E Elizabeth; Gómez-Zavaglia, Andrea

    2015-04-01

    The role of S-layer proteins (SLP) on the Pb(2+) sequestrant capacity by Lactobacillus kefir CIDCA 8348 and JCM 5818 was investigated. Cultures in the stationary phase were treated with proteinase K. A dot blot assay was carried out to assess the removal of SLP. Strains with and without SLP were exposed to 0-0.5 mM Pb(NO3)2. The maximum binding capacity (q max ) and the affinity coefficient (b) were calculated using the Langmuir equation. The structural effect of Pb(2+) on microorganisms with and without SLP was determined using Raman spectroscopy. The bacterial interaction with Pb(2+) led to a broadening in the phosphate bands (1,300-1,200 cm(-1) region) and strong alterations on amide and carboxylate-related bands (νCOO(-) as and νCOO(-) s). Microorganisms without SLP removed higher percentages of Pb(2+) and had higher q max than those bearing SLP. Isolated SLP had much lower q max and also removed lower percentages of Pb(2+) than the corresponding whole microorganisms. The hydrofobicity of both strains dramatically dropped when removing SLP. When bearing SLP, strains do not expose a large amount of charged groups on their surfaces, thus making less efficient the Pb(2+) removal. On the contrary, the extremely low hydrofobicity of microorganisms without SLP (and consequently, their higher capacity to remove Pb(2+)) can be explained on the basis of a greater exposure of charged chemical groups for the interaction with Pb(2+). The viability of bacteria without SLP was not significantly lower than that of bacteria bearing SLP. However, microorganisms without SLP were more prone to the detrimental effect of Pb(2+), thus suggesting that SLP acts as a protective rather than as a sequestrant layer.

  15. S-layer and cytoplasmic membrane – exceptions from the typical archaeal cell wall with a focus on double membranes

    Directory of Open Access Journals (Sweden)

    Andreas eKlingl

    2014-11-01

    Full Text Available The common idea of typical cell wall architecture in archaea consists of a pseudo-crystalline proteinaceous surface layer (S-layer, situated upon the cytoplasmic membrane. This is true for the majority of described archaea, hitherto. Within the crenarchaea, the S-layer often represents the only cell wall component, but there are various exceptions from this wall architecture. Beside (glycosylated S-layers in (hyperthermophilic cren- and euryarchaea as well as halophilic archaea, one can find a great variety of other cell wall structures like proteoglycan-like S-layers (Halobacteria, glutaminylglycan (Natronococci, methanochondroitin (Methanosarcina or double layered cell walls with pseudomurein (Methanothermus and Methanopyrus. The presence of an outermost cellular membrane in the crenarchaeal species Ignicoccus hospitalis already gave indications for an outer membrane similar to Gram-negative bacteria. Although there is just limited data concerning their biochemistry and ultrastructure, recent studies on the euryarchaeal methanogen Methanomassiliicoccus luminyensis, cells of the ARMAN group, and the SM1 euryarchaeon delivered further examples for this exceptional cell envelope type consisting of two membranes.

  16. Extending Cloud Management Tools at the IaaS and PaaS Layers for Cloud Interoperabitliy

    OpenAIRE

    Collell Martin, Oriol

    2013-01-01

    This project explores interoperability at the IaaS and PaaS layers of the Cloud Computing stack by contributing to two ongoing European research projects: Cloud4SOA and OPTIMIS. The contributions consist on connecting the platforms provided by both projects to new Cloud providers.

  17. Molecular Basis for the Attachment of S-Layer Proteins to the Cell Wall of Bacillus anthracis.

    Science.gov (United States)

    Sychantha, David; Chapman, Robert N; Bamford, Natalie C; Boons, Geert-Jan; Howell, P Lynne; Clarke, Anthony J

    2018-04-03

    Bacterial surface (S) layers are paracrystalline arrays of protein assembled on the bacterial cell wall that serve as protective barriers and scaffolds for housekeeping enzymes and virulence factors. The attachment of S-layer proteins to the cell walls of the Bacillus cereus sensu lato, which includes the pathogen Bacillus anthracis, occurs through noncovalent interactions between their S-layer homology domains and secondary cell wall polysaccharides. To promote these interactions, it is presumed that the terminal N-acetylmannosamine (ManNAc) residues of the secondary cell wall polysaccharides must be ketal-pyruvylated. For a few specific S-layer proteins, the O-acetylation of the penultimate N-acetylglucosamine (GlcNAc) is also required. Herein, we present the X-ray crystal structure of the SLH domain of the major surface array protein Sap from B. anthracis in complex with 4,6- O-ketal-pyruvyl-β-ManNAc-(1,4)-β-GlcNAc-(1,6)-α-GlcN. This structure reveals for the first time that the conserved terminal SCWP unit is the direct ligand for the SLH domain. Furthermore, we identify key binding interactions that account for the requirement of 4,6- O-ketal-pyruvyl-ManNAc while revealing the insignificance of the O-acetylation on the GlcNAc residue for recognition by Sap.

  18. A Highly Expressed High-Molecular-Weight S-Layer Complex of Pelosinus sp. Strain UFO1 Binds Uranium

    Energy Technology Data Exchange (ETDEWEB)

    Thorgersen, Michael P. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Lancaster, W. Andrew [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Rajeev, Lara [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biological Systems and Engineering Division; Ge, Xiaoxuan [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Vaccaro, Brian J. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Poole, Farris L. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology; Arkin, Adam P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biological Systems and Engineering Division; Mukhopadhyay, Aindrila [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Biological Systems and Engineering Division; Adams, Michael W. W. [Univ. of Georgia, Athens, GA (United States). Dept. of Biochemistry and Molecular Biology

    2016-12-02

    Cell suspensions of Pelosinus sp. strain UFO1 were previously shown, using spectroscopic analysis, to sequester uranium as U(IV) complexed with carboxyl and phosphoryl group ligands on proteins. The goal of our present study was to characterize the proteins involved in uranium binding. Virtually all of the uranium in UFO1 cells was associated with a heterodimeric protein, which was termed the uranium-binding complex (UBC). The UBC was composed of two S-layer domain proteins encoded by UFO1_4202 and UFO1_4203. Samples of UBC purified from the membrane fraction contained 3.3 U atoms/heterodimer, but significant amounts of phosphate were not detected. The UBC had an estimated molecular mass by gel filtration chromatography of 15 MDa, and it was proposed to contain 150 heterodimers (UFO1_4203 and UFO1_4202) and about 500 uranium atoms. The UBC was also the dominant extracellular protein, but when purified from the growth medium, it contained only 0.3 U atoms/heterodimer. The two genes encoding the UBC were among the most highly expressed genes within the UFO1 genome, and their expressions were unchanged by the presence or absence of uranium. Therefore, the UBC appears to be constitutively expressed and is the first line of defense against uranium, including by secretion into the extracellular medium. Although S-layer proteins were previously shown to bind U(VI), here we showed that U(IV) binds to S-layer proteins, we identified the proteins involved, and we quantitated the amount of uranium bound. Widespread uranium contamination from industrial sources poses hazards to human health and to the environment. Here in this paper, we identified a highly abundant uranium-binding complex (UBC) from Pelosinus sp. strain UFO1. The complex makes up the primary protein component of the S-layer of strain UFO1 and binds 3.3 atoms of U(IV) per heterodimer. Finally, while other bacteria have been shown to bind U(VI) on their S-layer, we demonstrate here an example of U(IV) bound by

  19. S-layer fusion protein as a tool functionalizing emulsomes and CurcuEmulsomes for antibody binding and targeting.

    Science.gov (United States)

    Ucisik, Mehmet H; Küpcü, Seta; Breitwieser, Andreas; Gelbmann, Nicola; Schuster, Bernhard; Sleytr, Uwe B

    2015-04-01

    Selective targeting of tumor cells by nanoparticle-based drug delivery systems is highly desirable because it maximizes the drug concentration at the desired target while simultaneously protecting the surrounding healthy tissues. Here, we show a design for smart nanocarriers based on a biomimetic approach that utilizes the building principle of virus envelope structures. Emulsomes and CurcuEmulsomes comprising a tripalmitin solid core surrounded by phospholipid layers are modified by S-layer proteins that self-assemble into a two-dimensional array to form a surface layer. One significant advantage of this nanoformulation is that it increases the solubility of the lipophilic anti-cancer agent curcumin in the CurcuEmulsomes by a factor of 2700. In order to make the emulsomes specific for IgG, the S-layer protein is fused with two protein G domains. This S-layer fusion protein preserves its recrystallization characteristics, forming an ordered surface layer (square lattice with 13 nm unit-by-unit distance). The GG domains are presented in a predicted orientation and exhibit a selective binding affinity for IgG. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

  20. Expression and cytosolic assembly of the S-layer fusion protein mSbsC-EGFP in eukaryotic cells

    Directory of Open Access Journals (Sweden)

    Veenhuis Marten

    2005-10-01

    Full Text Available Abstract Background Native as well as recombinant bacterial cell surface layer (S-layer protein of Geobacillus (G. stearothermophilus ATCC 12980 assembles to supramolecular structures with an oblique symmetry. Upon expression in E. coli, S-layer self assembly products are formed in the cytosol. We tested the expression and assembly of a fusion protein, consisting of the mature part (aa 31–1099 of the S-layer protein and EGFP (enhanced green fluorescent protein, in eukaryotic host cells, the yeast Saccharomyces cerevisiae and human HeLa cells. Results Upon expression in E. coli the recombinant mSbsC-EGFP fusion protein was recovered from the insoluble fraction. After denaturation by Guanidine (Gua-HCl treatment and subsequent dialysis the fusion protein assembled in solution and yielded green fluorescent cylindric structures with regular symmetry comparable to that of the authentic SbsC. For expression in the eukaryotic host Saccharomyces (S. cerevisiae mSbsC-EGFP was cloned in a multi-copy expression vector bearing the strong constitutive GPD1 (glyceraldehyde-3-phosophate-dehydrogenase promoter. The respective yeast transfomants were only slightly impaired in growth and exhibited a needle-like green fluorescent pattern. Transmission electron microscopy (TEM studies revealed the presence of closely packed cylindrical structures in the cytosol with regular symmetry comparable to those obtained after in vitro recrystallization. Similar structures are observed in HeLa cells expressing mSbsC-EGFP from the Cytomegalovirus (CMV IE promoter. Conclusion The mSbsC-EGFP fusion protein is stably expressed both in the yeast, Saccharomyces cerevisiae, and in HeLa cells. Recombinant mSbsC-EGFP combines properties of both fusion partners: it assembles both in vitro and in vivo to cylindrical structures that show an intensive green fluorescence. Fusion of proteins to S-layer proteins may be a useful tool for high level expression in yeast and HeLa cells of

  1. Lactobacillus helveticus MIMLh5-Specific Antibodies for Detection of S-Layer Protein in Grana Padano Protected-Designation-of-Origin Cheese

    Science.gov (United States)

    Brockmann, Eeva-Christine; Huovinen, Tuomas; Guglielmetti, Simone; Mora, Diego; Taverniti, Valentina; Arioli, Stefania; De Noni, Ivano; Lamminmäki, Urpo

    2014-01-01

    Single-chain variable-fragment antibodies (scFvs) have considerable potential in immunological detection and localization of bacterial surface structures. In this study, synthetic phage-displayed antibody libraries were used to select scFvs against immunologically active S-layer protein of Lactobacillus helveticus MIMLh5. After three rounds of panning, five relevant phage clones were obtained, of which four were specific for the S-layer protein of L. helveticus MIMLh5 and one was also capable of binding to the S-layer protein of L. helveticus ATCC 15009. All five anti-S-layer scFvs were expressed in Escherichia coli XL1-Blue, and their specificity profiles were characterized by Western blotting. The anti-S-layer scFv PolyH4, with the highest specificity for the S-layer protein of L. helveticus MIMLh5, was used to detect the S-layer protein in Grana Padano protected-designation-of-origin (PDO) cheese extracts by Western blotting. These results showed promising applications of this monoclonal antibody for the detection of immunomodulatory S-layer protein in dairy (and dairy-based) foods. PMID:24242242

  2. Analysis of the interaction between Bacillus coagulans and Bacillus thuringiensis S-layers and calcium ions by XRD, light microscopy, and FTIR.

    Science.gov (United States)

    Babolmorad, Ghazal; Emtiazi, Giti; Emamzadeh, Rahman

    2014-05-01

    S-layer is a self-assemble regularly crystalline surface that covers major cell wall component of many bacteria and archaea and exhibits a high metal-binding capacity. We have studied the effect of the calcium ions and type of solid support (glass or mica) on the structure of the S-layers from Bacillus coagulans HN-68 and Bacillus thuringiensis MH14 upon simple methods based on light microscopy and AFM. Furthermore, the Fourier transform infrared spectroscopy (FTIR) study is indicated that the calcium-S-layer interaction occurred mainly through the carboxylate groups of the side chains of aspartic acid (Asp) and glutamic acid (Glu) and nitrogen atoms of Lys, Asn, and histidine (His) amino acids and N-H groups of the peptide backbone. Studied FTIR revealed that inner faces of S-layer are mainly negative, and outer faces of S-layer are mainly positive. Probably, calcium ions with positive charges bound to the carboxyl groups of Glu and Asp. Accordingly, calcium ions are anchored in the space between the inner faces of S-layer with negative charge and the surface of mica with negative charge. This leads to regular arrangement of the S-layer subunits.

  3. Inhibition of H9N2 virus invasion into dendritic cells by the S-layer protein from L. acidophilus ATCC 4356

    Directory of Open Access Journals (Sweden)

    Xue Gao

    2016-10-01

    Full Text Available Probiotics are essential for the prevention of virus invasion and the maintenance of the immune balance. However, the mechanism of competition between probiotics and virus are unknown. The objectives of this study were to isolate the surface layer (S-layer protein from L. acidophilus ATCC 4356 as a new antiviral material, to evaluate the stimulatory effects of the S-layer protein on mouse dendritic cells (DCs and to verify its ability to inhibit the invasion of H9N2 avian influenza virus (AIV in DCs. We found that the S-layer protein induced DCs activation and up-regulated the IL-10 secretion. The invasion and replication of the H9N2 virus in mouse DCs was successfully demonstrated. However, the invasion of H9N2 virus into DCs could be inhibited by treatment with the S-layer protein prior to infection, which was verified by the reduced hemagglutinin (HA and neuraminidase (NA mRNA expression, and nucleoprotein (NP protein expression in the DCs. Furthermore, treatment with the S-layer protein increases the Mx1, Isg15, and Ddx58 mRNA expressions, and remits the inflammatory process to inhibit H9N2 AIV infection. In conclusion, the S-layer protein stimulates the activation of mouse DCs, inhibits H9N2 virus invasion of DCs, and stimulates the IFN-I signalling pathway. Thus, the S-layer protein from Lactobacillus is a promising biological antiviral material for AIV prevention.

  4. Exploitation of the S-layer self-assembly system for site directed immobilization of enzymes demonstrated for an extremophilic laminarinase from Pyrococcus furiosus

    Science.gov (United States)

    Tschiggerl, Helga; Breitwieser, Andreas; de Roo, Guy; Verwoerd, Theo; Scḧaffer, Christina; Sleytr, Uwe B.

    2015-01-01

    A fusion protein based on the S-layer protein SbpA from Bacillus sphaericus CCM 2177 and the enzyme laminarinase (LamA) from Pyrococcus furiosus was designed and overexpressed in Escherichia coli. Due to the construction principle, the S-layer fusion protein fully retained the self-assembly capability of the S-layer moiety, while the catalytic domain of LamA remained exposed at the outer surface of the formed protein lattice. The enzyme activity of the S-layer fusion protein monolayer obtained upon recrystallization on silicon wafers, glass slides and different types of polymer membranes was determined colorimetrically and related to the activity of sole LamA that has been immobilized with conventional techniques. LamA aligned within the S-layer fusion protein lattice in a periodic and orientated fashion catalyzed twice the glucose release from the laminarin polysaccharide substrate in comparison to the randomly immobilized enzyme. In combination with the good shelf-life and the high resistance towards temperature and diverse chemicals, these novel composites are regarded a promising approach for site-directed enzyme immobilization. PMID:18035441

  5. Lactobacillus buchneri S-layer as carrier for an Ara h 2-derived peptide for peanut allergen-specific immunotherapy.

    Science.gov (United States)

    Anzengruber, Julia; Bublin, Merima; Bönisch, Eva; Janesch, Bettina; Tscheppe, Angelika; Braun, Matthias L; Varga, Eva-Maria; Hafner, Christine; Breiteneder, Heimo; Schäffer, Christina

    2017-05-01

    Peanut allergy is an IgE-mediated severe hypersensitivity disorder. The lack of a treatment of this potentially fatal allergy has led to intensive research on vaccine development. Here, we describe the design and initial characterization of a carrier-bound peptide derived from the most potent peanut allergen, Ara h 2, as a candidate vaccine. Based on the adjuvant capability of bacterial surface (S-) layers, a fusion protein of the S-layer protein SlpB from Lactobacillus buchneri CD034 and the Ara h 2-derived peptide AH3a42 was produced. This peptide comprised immunodominant B-cell epitopes as well as one T cell epitope. The fusion protein SlpB-AH3a42 was expressed in E. coli, purified, and tested for its IgE binding capacity as well as for its ability to activate sensitized rat basophil leukemia (RBL) cells. The capacity of Ara h 2-specific IgG rabbit-antibodies raised against SlpB-AH3a42 or Ara h 2 to inhibit IgE-binding was determined by ELISA inhibition assays using sera of peanut allergic patients sensitized to Ara h 2. IgE specific to the SlpB-AH3a42 fusion protein was detected in 69% (25 of 36) of the sera. Despite the recognition by IgE, the SlpB-AH3a42 fusion protein was unable to induce β-hexosaminidase release from sensitized RBL cells at concentrations up to 100ng per ml. The inhibition of IgE-binding to the natural allergen observed after pre-incubation of the 20 sera with rabbit anti-SlpB-AH3a42 IgG was more than 30% for four sera, more than 20% for eight sera, and below 10% for eight sera. In comparison, anti-Ara h 2 rabbit IgG antibodies inhibited binding to Ara h 2 by 48% ±13.5%. Our data provide evidence for the feasibility of this novel approach towards the development of a peanut allergen peptide-based carrier-bound vaccine. Our experiments further indicate that more than one allergen-peptide will be needed to induce a broader protection of patients allergic to Ara h 2. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights

  6. Heterologous protein display on the cell surface of lactic acid bacteria mediated by the s-layer protein

    Directory of Open Access Journals (Sweden)

    Han Lanlan

    2011-10-01

    Full Text Available Abstract Background Previous studies have revealed that the C-terminal region of the S-layer protein from Lactobacillus is responsible for the cell wall anchoring, which provide an approach for targeting heterologous proteins to the cell wall of lactic acid bacteria (LAB. In this study, we developed a new surface display system in lactic acid bacteria with the C-terminal region of S-layer protein SlpB of Lactobacillus crispatus K2-4-3 isolated from chicken intestine. Results Multiple sequence alignment revealed that the C-terminal region (LcsB of Lb. crispatus K2-4-3 SlpB had a high similarity with the cell wall binding domains SA and CbsA of Lactobacillus acidophilus and Lb. crispatus. To evaluate the potential application as an anchoring protein, the green fluorescent protein (GFP or beta-galactosidase (Gal was fused to the N-terminus of the LcsB region, and the fused proteins were successfully produced in Escherichia coli, respectively. After mixing them with the non-genetically modified lactic acid bacteria cells, the fused GFP-LcsB and Gal-LcsB were functionally associated with the cell surface of various lactic acid bacteria tested. In addition, the binding capacity could be improved by SDS pretreatment. Moreover, both of the fused proteins could simultaneously bind to the surface of a single cell. Furthermore, when the fused DNA fragment of gfp:lcsB was inserted into the Lactococcus lactis expression vector pSec:Leiss:Nuc, the GFP could not be secreted into the medium under the control of the nisA promoter. Western blot, in-gel fluorescence assay, immunofluorescence microscopy and SDS sensitivity analysis confirmed that the GFP was successfully expressed onto the cell surface of L. lactis with the aid of the LcsB anchor. Conclusion The LcsB region can be used as a functional scaffold to target the heterologous proteins to the cell surfaces of lactic acid bacteria in vitro and in vivo, and has also the potential for biotechnological

  7. Archaea S-layer nanotube from a "black smoker" in complex with cyclo-octasulfur (S8) rings.

    Science.gov (United States)

    McDougall, Matthew; Francisco, Olga; Harder-Viddal, Candice; Roshko, Roy; Meier, Markus; Stetefeld, Jörg

    2017-12-01

    Elemental sulfur exists primarily as an S80 ring and serves as terminal electron acceptor for a variety of sulfur-fermenting bacteria. Hyperthermophilic archaea from black smoker vents are an exciting research tool to advance our knowledge of sulfur respiration under extreme conditions. Here, we use a hybrid method approach to demonstrate that the proteinaceous cavities of the S-layer nanotube of the hyperthermophilic archaeon Staphylothermus marinus act as a storage reservoir for cyclo-octasulfur S8. Fully atomistic molecular dynamics (MD) simulations were performed and the method of multiconfigurational thermodynamic integration was employed to compute the absolute free energy for transferring a ring of elemental sulfur S8 from an aqueous bath into the largest hydrophobic cavity of a fragment of archaeal tetrabrachion. Comparisons with earlier MD studies of the free energy of hydration as a function of water occupancy in the same cavity of archaeal tetrabrachion show that the sulfur ring is energetically favored over water. © 2017 Wiley Periodicals, Inc.

  8. Calcium dependent formation of tubular assemblies by recombinant S-layer proteins in vivo and in vitro

    Energy Technology Data Exchange (ETDEWEB)

    Korkmaz, Nuriye; Ostermann, Kai; Roedel, Gerhard, E-mail: nuriye_korkmaz@yahoo.com, E-mail: kai.ostermann@tu-dresden.de, E-mail: gerhard.roedel@tu-dresden.de [Institut fuer Genetik, Technische Universitaet Dresden, Zellescher Weg 20b, 01217 Dresden (Germany)

    2011-03-04

    Surface layer proteins have the appealing property to self-assemble in nanosized arrays in solution and on solid substrates. In this work, we characterize the formation of assembly structures of the recombinant surface layer protein SbsC of Geobacillus stearothermophilus ATTC 12980, which was tagged with enhanced green fluorescent protein and expressed in the yeast Saccharomyces cerevisiae. The tubular structures formed by the protein in vivo are retained upon bursting the cells by osmotic shock; however, their average length is decreased. During dialysis, monomers obtained by treatment with chaotropic chemicals recrystallize again to form tube-like structures. This process is strictly dependent on calcium (Ca{sup 2+}) ions, with an optimal concentration of 10 mM. Further increase of the Ca{sup 2+} concentration results in multiple non-productive nucleation points. We further show that the lengths of the S-layer assemblies increase with time and can be controlled by pH. After 48 h, the average length at pH 9.0 is 4.13 {mu}m compared to 2.69 {mu}m at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications.

  9. Calcium dependent formation of tubular assemblies by recombinant S-layer proteins in vivo and in vitro

    International Nuclear Information System (INIS)

    Korkmaz, Nuriye; Ostermann, Kai; Roedel, Gerhard

    2011-01-01

    Surface layer proteins have the appealing property to self-assemble in nanosized arrays in solution and on solid substrates. In this work, we characterize the formation of assembly structures of the recombinant surface layer protein SbsC of Geobacillus stearothermophilus ATTC 12980, which was tagged with enhanced green fluorescent protein and expressed in the yeast Saccharomyces cerevisiae. The tubular structures formed by the protein in vivo are retained upon bursting the cells by osmotic shock; however, their average length is decreased. During dialysis, monomers obtained by treatment with chaotropic chemicals recrystallize again to form tube-like structures. This process is strictly dependent on calcium (Ca 2+ ) ions, with an optimal concentration of 10 mM. Further increase of the Ca 2+ concentration results in multiple non-productive nucleation points. We further show that the lengths of the S-layer assemblies increase with time and can be controlled by pH. After 48 h, the average length at pH 9.0 is 4.13 μm compared to 2.69 μm at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications.

  10. Calcium dependent formation of tubular assemblies by recombinant S-layer proteins in vivo and in vitro

    Science.gov (United States)

    Korkmaz, Nuriye; Ostermann, Kai; Rödel, Gerhard

    2011-03-01

    Surface layer proteins have the appealing property to self-assemble in nanosized arrays in solution and on solid substrates. In this work, we characterize the formation of assembly structures of the recombinant surface layer protein SbsC of Geobacillus stearothermophilus ATTC 12980, which was tagged with enhanced green fluorescent protein and expressed in the yeast Saccharomyces cerevisiae. The tubular structures formed by the protein in vivo are retained upon bursting the cells by osmotic shock; however, their average length is decreased. During dialysis, monomers obtained by treatment with chaotropic chemicals recrystallize again to form tube-like structures. This process is strictly dependent on calcium (Ca2 + ) ions, with an optimal concentration of 10 mM. Further increase of the Ca2 + concentration results in multiple non-productive nucleation points. We further show that the lengths of the S-layer assemblies increase with time and can be controlled by pH. After 48 h, the average length at pH 9.0 is 4.13 µm compared to 2.69 µm at pH 5.5. Successful chemical deposition of platinum indicates the potential of recrystallized mSbsC-eGFP structures for nanobiotechnological applications.

  11. The S-layer Associated Serine Protease Homolog PrtX Impacts Cell Surface-Mediated Microbe-Host Interactions of Lactobacillus acidophilus NCFM

    Directory of Open Access Journals (Sweden)

    Brant R. Johnson

    2017-06-01

    Full Text Available Health-promoting aspects attributed to probiotic microorganisms, including adhesion to intestinal epithelia and modulation of the host mucosal immune system, are mediated by proteins found on the bacterial cell surface. Notably, certain probiotic and commensal bacteria contain a surface (S- layer as the outermost stratum of the cell wall. S-layers are non-covalently bound semi-porous, crystalline arrays of self-assembling, proteinaceous subunits called S-layer proteins (SLPs. Recent evidence has shown that multiple proteins are non-covalently co-localized within the S-layer, designated S-layer associated proteins (SLAPs. In Lactobacillus acidophilus NCFM, SLP and SLAPs have been implicated in both mucosal immunomodulation and adhesion to the host intestinal epithelium. In this study, a S-layer associated serine protease homolog, PrtX (prtX, lba1578, was deleted from the chromosome of L. acidophilus NCFM. Compared to the parent strain, the PrtX-deficient strain (ΔprtX demonstrated increased autoaggregation, an altered cellular morphology, and pleiotropic increases in adhesion to mucin and fibronectin, in vitro. Furthermore, ΔprtX demonstrated increased in vitro immune stimulation of IL-6, IL-12, and IL-10 compared to wild-type, when exposed to mouse dendritic cells. Finally, in vivo colonization of germ-free mice with ΔprtX led to an increase in epithelial barrier integrity. The absence of PrtX within the exoproteome of a ΔprtX strain caused morphological changes, resulting in a pleiotropic increase of the organisms’ immunomodulatory properties and interactions with some intestinal epithelial cell components.

  12. Sporadic E S Layers at High Latitudes During a Magnetic Storm of March 17, 2015 According to the Vertical and Oblique Ionospheric Sounding Data

    Science.gov (United States)

    Blagoveshchensky, D. V.; Maltseva, O. A.; Anishin, M. M.; Rogov, D. D.

    2017-11-01

    We consider the behavior of the parameters of the ionospheric E s layers according to the vertical sounding at the Sodankylä observatory and oblique sounding at the Lovozero (Murmansk region)—Gor'kovskaya station (Leningrad region) path during a superstorm of March 17, 2015. Temporal and spatial behavior of these parameters is compared. It was found that the storm significantly distorted the normal course of variations of the sporadic E s layer characteristics. Specific behavior of the layers during a storm at points separated by about 300 km was detected. With the help of ray tracing calculations using the IRI model, oblique sounding ionograms were constructed for the radio path analyzed. Primary attention is given to the maximum usable frequency of the F 2 layer—MUF- F 2. Additionally, for the disturbed conditions where there is only a high-power E s layer on the experimental ionograms, the values of MUF- E s and the ratio K =MUF- E s/ f o E s for various cutoff frequencies f o E s of the E s layer and its altitudes {h}_{E_s} are calculated within the framework of the well-known approximations. Calculations for the case of weak disturbance and semitransparent E s layers are carried out with the IRI model adapted to the current diagnostics parameters. It was found that the calculated and experimental values of MUF- F 2 are close to each other or coincide, while this cannot be said about MUF- E s. The calculated and experimental values of MUF- E s can be matched in the model of mirror reflection from a flat layer for intense layers and the model of the E layer for thick E s layers of low intensity.

  13. Mapping of Monoclonal Antibody Binding Sites on CNBr Fragments of the S- Layer Protein Antigens of Rickettsia Typhi and Rickettsia Prowazekii

    Science.gov (United States)

    1992-01-01

    Security Clasification ) Mapping of monoclonal antibody binding sites on CNBr fragments o; the S-layer protein antigens of Rickettsia Typhi and...homology was found in all the viral polypeptides have long fatty acids attached to fragments which react with type I antibody (Fig. 4). A their N-termini

  14. Interchange of the active and silent S-layer protein genes of Lactobacillus acidophilus by inversion of the chromosomal sip segment

    NARCIS (Netherlands)

    Boot, H.J.; Kolen, C.P.A.M.; Pouwels, P.H.

    1996-01-01

    The most-dominant surface-exposed protein in many bacterial species is the S-protein. This protein crystallises into a regular monolayer on the outside surface of the bacteria: the S-layer. Lactobacillus acidophilus harbours two S-protein-encoding genes, slpA and slpB, only one of which (slpA) is

  15. Balanced transcription of cell division genes in Bacillus subtilis as revealed by single cell analysis

    NARCIS (Netherlands)

    Trip, Erik Nico; Veening, Jan-Willem; Stewart, Eric J.; Errington, Jeff; Scheffers, Dirk-Jan

    2013-01-01

    Cell division in bacteria is carried out by a set of conserved proteins that all have to function at the correct place and time. A cell cycle-dependent transcriptional programme drives cell division in bacteria such as Caulobacter crescentus. Whether such a programme exists in the Gram-positive

  16. Transposon Tn5 encodes streptomycin resistance in nonenteric bacteria.

    OpenAIRE

    O'Neill, E A; Kiely, G M; Bender, R A

    1984-01-01

    Strains of Caulobacter crescentus, Pseudomonas putida, Acinetobacter calcoaceticus, Rhizobium meliloti, and Rhodopseudomonas sphaeroides carrying the kanamycin resistance-encoding transposon Tn5 were 15 to 500 times more resistant to streptomycin than transposon-free strains. The streptomycin resistance determinant, which is separable from the kanamycin resistance determinant of Tn5, was not expressed in Escherichia coli or Klebsiella aerogenes.

  17. A role for the weak DnaA binding sites in bacterial replication origins

    DEFF Research Database (Denmark)

    Charbon, Godefroid; Løbner-Olesen, Anders

    2011-01-01

    between species. In the study by Taylor et al. (2011), new and unexpectedly weak DnaA-boxes were identified within the Caulobacter crescentus origin of replication (Cori). The position of weak and stronger DnaA-boxes follows a pattern seen in Escherichia coli oriC. This raises the possibility...... that bacterial origins might be more alike than previously thought....

  18. Establishment of oxidative D-xylose metabolism in Pseudomonas putida S12

    NARCIS (Netherlands)

    Meijnen, J.P.; Winde, J.H. de; Ruijssenaars, H.J.

    2009-01-01

    The oxidative D-xylose catabolic pathway of Caulobacter crescentus, encoded by the xylXABCD operon, was expressed in the gram-negative bacterium Pseudomonas putida S12. This engineered transformant strain was able to grow on D-xylose as a sole carbon source with a biomass yield of 53% (based on g

  19. In situ variations of the scintillation characteristics in GaN and CdS layers under irradiation by 1.6 MeV protons

    Energy Technology Data Exchange (ETDEWEB)

    Gaubas, E., E-mail: eugenijus.gaubas@ff.vu.lt; Ceponis, T.; Pavlov, J.; Tekorius, A.

    2015-12-15

    Evolution of the non-radiative and radiative recombination in GaN and CdS 2.5–20 μm thick layers has been examined by the in situ measurements of the 1.6 MeV proton induced luminescence and laser excited photoconductivity characteristics. The introduction rate of radiation defects has been evaluated by the comparative analysis of the laser and proton beam induced luminescence for the examined GaN and CdS layers.

  20. The S-Layer Proteins of Two Bacillus stearothermophilus Wild-Type Strains Are Bound via Their N-Terminal Region to a Secondary Cell Wall Polymer of Identical Chemical Composition

    Science.gov (United States)

    Egelseer, Eva Maria; Leitner, Karl; Jarosch, Marina; Hotzy, Christoph; Zayni, Sonja; Sleytr, Uwe B.; Sára, Margit

    1998-01-01

    Two Bacillus stearothermophilus wild-type strains were investigated regarding a common recognition and binding mechanism between the S-layer protein and the underlying cell envelope layer. The S-layer protein from B. stearothermophilus PV72/p6 has a molecular weight of 130,000 and assembles into a hexagonally ordered lattice. The S-layer from B. stearothermophilus ATCC 12980 shows oblique lattice symmetry and is composed of subunits with a molecular weight of 122,000. Immunoblotting, peptide mapping, N-terminal sequencing of the whole S-layer protein from B. stearothermophilus ATCC 12980 and of proteolytic cleavage fragments, and comparison with the S-layer protein from B. stearothermophilus PV72/p6 revealed that the two S-layer proteins have identical N-terminal regions but no other extended structurally homologous domains. In contrast to the heterogeneity observed for the S-layer proteins, the secondary cell wall polymer isolated from peptidoglycan-containing sacculi of the different strains showed identical chemical compositions and comparable molecular weights. The S-layer proteins could bind and recrystallize into the appropriate lattice type on native peptidoglycan-containing sacculi from both organisms but not on those extracted with hydrofluoric acid, leading to peptidoglycan of the A1γ chemotype. Affinity studies showed that only proteolytic cleavage fragments possessing the complete N terminus of the mature S-layer proteins recognized native peptidoglycan-containing sacculi as binding sites or could associate with the isolated secondary cell wall polymer, while proteolytic cleavage fragments missing the N-terminal region remained unbound. From the results obtained in this study, it can be concluded that S-layer proteins from B. stearothermophilus wild-type strains possess an identical N-terminal region which is responsible for anchoring the S-layer subunits to a secondary cell wall polymer of identical chemical composition. PMID:9515918

  1. Identification of Two Binding Domains, One for Peptidoglycan and Another for a Secondary Cell Wall Polymer, on the N-Terminal Part of the S-Layer Protein SbsB from Bacillus stearothermophilus PV72/p2

    Science.gov (United States)

    Sára, Margit; Egelseer, Eva M.; Dekitsch, Christine; Sleytr, Uwe B.

    1998-01-01

    First studies on the structure-function relationship of the S-layer protein from B. stearothermophilus PV72/p2 revealed the coexistence of two binding domains on its N-terminal part, one for peptidoglycan and another for a secondary cell wall polymer (SCWP). The peptidoglycan binding domain is located between amino acids 1 to 138 of the mature S-layer protein comprising a typical S-layer homologous domain. The SCWP binding domain lies between amino acids 240 to 331 and possesses a high serine plus glycine content. PMID:9852032

  2. Biosynthesis and Role of N-Linked Glycosylation in Cell Surface Structures of Archaea with a Focus on Flagella and S Layers

    Directory of Open Access Journals (Sweden)

    Ken F. Jarrell

    2010-01-01

    Full Text Available The genetics and biochemistry of the N-linked glycosylation system of Archaea have been investigated over the past 5 years using flagellins and S layers as reporter proteins in the model organisms, Methanococcus voltae, Methanococcus maripaludis, and Haloferax volcanii. Structures of archaeal N-linked glycans have indicated a variety of linking sugars as well as unique sugar components. In M. voltae, M. maripaludis, and H. volcanii, a number of archaeal glycosylation genes (agl have been identified by deletion and complementation studies. These include many of the glycosyltransferases and the oligosaccharyltransferase needed to assemble the glycans as well as some of the genes encoding enzymes required for the biosynthesis of the sugars themselves. The N-linked glycosylation system is not essential for any of M. voltae, M. maripaludis, or H. volcanii, as demonstrated by the successful isolation of mutants carrying deletions in the oligosaccharyltransferase gene aglB (a homologue of the eukaryotic Stt3 subunit of the oligosaccharyltransferase complex. However, mutations that affect the glycan structure have serious effects on both flagellation and S layer function.

  3. Bacterial Cell Surface Adsorption of Rare Earth Elements

    Science.gov (United States)

    Jiao, Y.; Park, D.; Reed, D.; Fujita, Y.; Yung, M.; Anderko, A.; Eslamimanesh, A.

    2015-12-01

    Rare earth elements (REE) play a critical role in many emerging clean energy technologies, including high-power magnets, wind turbines, solar panels, hybrid/electric vehicle batteries and lamp phosphors. In order to sustain demand for such technologies given current domestic REE shortages, there is a need to develop new approaches for ore processing/refining and recycling of REE-containing materials. To this end, we have developed a microbially-mediated bioadsorption strategy with application towards enrichment of REE from complex mixtures. Specifically, the bacterium Caulobacter crescentus was genetically engineered to display lanthanide binding tags (LBTs), short peptides that possess high affinity and specificity for rare earth elements, on its cell surface S-layer protein. Under optimal conditions, LBT-displayed cells adsorbed greater than 5-fold more REE than control cells lacking LBTs. Competition binding experiments with a selection of REEs demonstrated that our engineered cells could facilitate separation of light- from heavy- REE. Importantly, binding of REE onto our engineered strains was much more favorable compared to non-REE metals. Finally, REE bound to the cell surface could be stripped off using citrate, providing an effective and non-toxic REE recovery method. Together, this data highlights the potential of our approach for selective REE enrichment from REE containing mixtures.

  4. Bioadsorption of Rare Earth Elements through Cell Surface Display of Lanthanide Binding Tags.

    Science.gov (United States)

    Park, Dan M; Reed, David W; Yung, Mimi C; Eslamimanesh, Ali; Lencka, Malgorzata M; Anderko, Andrzej; Fujita, Yoshiko; Riman, Richard E; Navrotsky, Alexandra; Jiao, Yongqin

    2016-03-01

    With the increasing demand for rare earth elements (REEs) in many emerging clean energy technologies, there is an urgent need for the development of new approaches for efficient REE extraction and recovery. As a step toward this goal, we genetically engineered the aerobic bacterium Caulobacter crescentus for REE adsorption through high-density cell surface display of lanthanide binding tags (LBTs) on its S-layer. The LBT-displayed strains exhibited enhanced adsorption of REEs compared to cells lacking LBT, high specificity for REEs, and an adsorption preference for REEs with small atomic radii. Adsorbed Tb(3+) could be effectively recovered using citrate, consistent with thermodynamic speciation calculations that predicted strong complexation of Tb(3+) by citrate. No reduction in Tb(3+) adsorption capacity was observed following citrate elution, enabling consecutive adsorption/desorption cycles. The LBT-displayed strain was effective for extracting REEs from the acid leachate of core samples collected at a prospective rare earth mine. Our collective results demonstrate a rapid, efficient, and reversible process for REE adsorption with potential industrial application for REE enrichment and separation.

  5. Vanillic acid from Actinidia deliciosa impedes virulence in Serratia marcescens by affecting S-layer, flagellin and fatty acid biosynthesis proteins.

    Science.gov (United States)

    Sethupathy, Sivasamy; Ananthi, Sivagnanam; Selvaraj, Anthonymuthu; Shanmuganathan, Balakrishnan; Vigneshwari, Loganathan; Balamurugan, Krishnaswamy; Mahalingam, Sundarasamy; Pandian, Shunmugiah Karutha

    2017-11-27

    Serratia marcescens is one of the important nosocomial pathogens which rely on quorum sensing (QS) to regulate the production of biofilm and several virulence factors. Hence, blocking of QS has become a promising approach to quench the virulence of S. marcescens. For the first time, QS inhibitory (QSI) and antibiofilm potential of Actinidia deliciosa have been explored against S. marcescens clinical isolate (CI). A. deliciosa pulp extract significantly inhibited the virulence and biofilm production without any deleterious effect on the growth. Vanillic acid was identified as an active lead responsible for the QSI activity. Addition of vanillic acid to the growth medium significantly affected the QS regulated production of biofilm and virulence factors in a concentration dependent mode in S. marcescens CI, ATCC 14756 and MG1. Furthermore vanillic acid increased the survival of Caenorhabditis elegans upon S. marcescens infection. Proteomic analysis and mass spectrometric identification of differentially expressed proteins revealed the ability of vanillic acid to modulate the expression of proteins involved in S-layers, histidine, flagellin and fatty acid production. QSI potential of the vanillic acid observed in the current study paves the way for exploring it as a potential therapeutic candidate to treat S. marcescens infections.

  6. The S-Layer Glycoprotein of the Crenarchaeote Sulfolobus acidocaldarius Is Glycosylated at Multiple Sites with Chitobiose-Linked N-Glycans

    Directory of Open Access Journals (Sweden)

    Elham Peyfoon

    2010-01-01

    Full Text Available Glycosylation of the S-layer of the crenarchaea Sulfolobus acidocaldarius has been investigated using glycoproteomic methodologies. The mature protein is predicted to contain 31 N-glycosylation consensus sites with approximately one third being found in the C-terminal domain spanning residues L1004-Q1395. Since this domain is rich in Lys and Arg and therefore relatively tractable to glycoproteomic analysis, this study has focused on mapping its N-glycosylation. Our analysis identified nine of the 11 consensus sequence sites, and all were found to be glycosylated. This constitutes a remarkably high glycosylation density in the C-terminal domain averaging one site for each stretch of 30–40 residues. Each of the glycosylation sites observed was shown to be modified with a heterogeneous family of glycans, with the largest having a composition Glc1Man2GlcNAc2 plus 6-sulfoquinovose (QuiS, consistent with the tribranched hexasaccharide previously reported in the cytochrome b558/566 of S. acidocaldarius. S. acidocaldarius is the only archaeal species whose N-glycans are known to be linked via the chitobiose core disaccharide that characterises the N-linked glycans of Eukarya.

  7. Nucleotide Sequences and Comparison of Two Large Conjugative Plasmids from Different Campylobacter species

    Science.gov (United States)

    2004-01-01

    Campylobacter were grown on Mueller–Hinton (MH) medium at 42 or 37 uC under microaerobic conditions in the presence of the following antibiotics, when appro...described in this manuscript (data not shown) (Taylor et al., 1986). The tet(O) gene shares significant homology with the tet(M) gene of Streptococcus ...Burkholderia cepacia; C. jejuni, Campylobacter jejuni; C. crescentus, Caulobacter crescen- tus; C. hutchinsonii, Cytophaga hutchinsonii; E. faecalis

  8. Haloferax volcanii archaeosortase is required for motility, mating, and C-terminal processing of the S-layer glycoprotein: Haloferax volcanii archeosortase

    Energy Technology Data Exchange (ETDEWEB)

    Abdul Halim, Mohd Farid [University of Pennsylvania, Department of Biology, Philadelphia, PA, 19104, USA; Pfeiffer, Friedhelm [Department of Membrane Biochemistry, Max-Planck-Institute of Biochemistry, 82152, Martinsried, Germany; Zou, James [University of Pennsylvania, Department of Biology, Philadelphia, PA, 19104, USA; Frisch, Andrew [University of Pennsylvania, Department of Biology, Philadelphia, PA, 19104, USA; Haft, Daniel [J. Craig Venter Institute, Rockville, MD, 20850, USA; Wu, Si [Environmental Molecular Sciences Laboratory, Richland, WA, USA; Tolić, Nikola [Environmental Molecular Sciences Laboratory, Richland, WA, USA; Brewer, Heather [Environmental Molecular Sciences Laboratory, Richland, WA, USA; Payne, Samuel H. [Division of Biological Sciences, Pacific Northwest National Laboratory, Richland, WA, USA; Paša-Tolić, Ljiljana [Environmental Molecular Sciences Laboratory, Richland, WA, USA; Pohlschroder, Mechthild [University of Pennsylvania, Department of Biology, Philadelphia, PA, 19104, USA

    2013-05-28

    Cell surfaces are decorated by a variety of proteins that facilitate interactions with their environments and support cell stability.These secreted proteins are anchored to the cell by mechanisms that are diverse, and, in archaea, poorly understood. Recently published in silico data suggest that in some species a subset of secreted euryarchaeal proteins, which includes the S-­layer glycoprotein, is processed and covalently linked tot he cell membrane by enzymes referred to as archaeosortases. In silico work led to the proposal that an independent, sortase-like system for proteolysis-coupled carboxy-terminal lipid modification exists in bacteria (exosortase) and archaea (archaeosortase). Here, we provide the first in vivo characterization of an archaeosortase in the haloarchaeal model organism Haloferax volcanii. Deletion of the artA gene (HVO_0915) resulted in multiple biological phenotypes: (a) poor growth, especially under low-salt conditions, (b) alterations in cell shape and the S-layer, (c) impaired motility, suppressors of which still exhibit poor growth, and (d) impaired conjugation. We studied one of the ArtA substrates, the S-layer glycoprotein, using detailed proteomic analysis. While the carboxy-terminal region of S-layer glycoproteins, consisting of a threonine-rich O-glycosylated region followed by a hydrophobic transmembrane helix, has been notoriously resistant to any proteomic peptide identification, we were able to identify two overlapping peptides from the transmembrane domain present in the ΔartA strain but not in the wild-type strain. This clearly shows that ArtA is involved in carboxy-terminal posttranslational processing of the S-layer glycoprotein. As it is known from previous studies that a lipid is covalently attached to the carboxy-terminal region of the S-layer glycoprotein, our data strongly support the conclusion that archaeosortase functions analogously to sortase, mediating proteolysis-coupled, covalent cell surface attachment.

  9. Characterization of CBD-CdS layers with different S/Cd ratios in the chemical bath and their relation with the efficiency of CdS/CdTe solar cells

    International Nuclear Information System (INIS)

    Vigil-Galan, O.; Morales-Acevedo, A.; Cruz-Gandarilla, F.; Jimenez-Escamilla, M.G.; Aguilar-Hernandez, J.; Contreras-Puente, G.; Sastre-Hernandez, J.; Sanchez-Meza, E.; Ramon-Garcia, M.L.

    2007-01-01

    In previous papers we have reported the improvement of the efficiency of CdS/CdTe solar cells by varying the thiourea/CdCl 2 ratio (R tc ) in the chemical bath solution used for the deposition of the CdS layers. In this work, a more complete study concerning the physical properties of Chemical Bath Deposited (CBD) CdS layers studied by photoluminescence, X-ray diffraction and optical spectroscopy are correlated to the I-V characteristics under AM 1.5 sunlight and the spectral response of CdS/CdTe solar cells. It is confirmed that the optimum R tc for the CBD CdS films is R tc = 5, since in this case the best solar cells were obtained and these films show the better optical and structural characteristics

  10. Genetic evidence for the involvement of the S-layer protein gene sap and the sporulation genes spo0A, spo0B, and spo0F in Phage AP50c infection of Bacillus anthracis.

    Science.gov (United States)

    Plaut, Roger D; Beaber, John W; Zemansky, Jason; Kaur, Ajinder P; George, Matroner; Biswas, Biswajit; Henry, Matthew; Bishop-Lilly, Kimberly A; Mokashi, Vishwesh; Hannah, Ryan M; Pope, Robert K; Read, Timothy D; Stibitz, Scott; Calendar, Richard; Sozhamannan, Shanmuga

    2014-03-01

    In order to better characterize the Bacillus anthracis typing phage AP50c, we designed a genetic screen to identify its bacterial receptor. Insertions of the transposon mariner or targeted deletions of the structural gene for the S-layer protein Sap and the sporulation genes spo0A, spo0B, and spo0F in B. anthracis Sterne resulted in phage resistance with concomitant defects in phage adsorption and infectivity. Electron microscopy of bacteria incubated with AP50c revealed phage particles associated with the surface of bacilli of the Sterne strain but not with the surfaces of Δsap, Δspo0A, Δspo0B, or Δspo0F mutants. The amount of Sap in the S layer of each of the spo0 mutant strains was substantially reduced compared to that of the parent strain, and incubation of AP50c with purified recombinant Sap led to a substantial reduction in phage activity. Phylogenetic analysis based on whole-genome sequences of B. cereus sensu lato strains revealed several closely related B. cereus and B. thuringiensis strains that carry sap genes with very high similarities to the sap gene of B. anthracis. Complementation of the Δsap mutant in trans with the wild-type B. anthracis sap or the sap gene from either of two different B. cereus strains that are sensitive to AP50c infection restored phage sensitivity, and electron microscopy confirmed attachment of phage particles to the surface of each of the complemented strains. Based on these data, we postulate that Sap is involved in AP50c infectivity, most likely acting as the phage receptor, and that the spo0 genes may regulate synthesis of Sap and/or formation of the S layer.

  11. Coordination of division and development influences complex multicellular behavior in Agrobacterium tumefaciens.

    Directory of Open Access Journals (Sweden)

    Jinwoo Kim

    Full Text Available The α-Proteobacterium Agrobacterium tumefaciens has proteins homologous to known regulators that govern cell division and development in Caulobacter crescentus, many of which are also conserved among diverse α-Proteobacteria. In light of recent work demonstrating similarity between the division cycle of C. crescentus and that of A. tumefaciens, the functional conservation for this presumptive control pathway was examined. In C. crescentus the CtrA response regulator serves as the master regulator of cell cycle progression and cell division. CtrA activity is controlled by an integrated pair of multi-component phosphorelays: PleC/DivJ-DivK and CckA-ChpT-CtrA. Although several of the conserved orthologues appear to be essential in A. tumefaciens, deletions in pleC or divK were isolated and resulted in cell division defects, diminished swimming motility, and a decrease in biofilm formation. A. tumefaciens also has two additional pleC/divJhomologue sensor kinases called pdhS1 and pdhS2, absent in C. crescentus. Deletion of pdhS1 phenocopied the ΔpleC and ΔdivK mutants. Cells lacking pdhS2 morphologically resembled wild-type bacteria, but were decreased in swimming motility and elevated for biofilm formation, suggesting that pdhS2 may serve to regulate the motile to non-motile switch in A. tumefaciens. Genetic analysis suggests that the PleC/DivJ-DivK and CckA-ChpT-CtrA phosphorelays in A. tumefaciens are vertically-integrated, as in C. crescentus. A gain-of-function mutation in CckA (Y674D was identified as a spontaneous suppressor of the ΔpleC motility phenotype. Thus, although the core architecture of the A. tumefaciens pathway resembles that of C. crescentus there are specific differences including additional regulators, divergent pathway architecture, and distinct target functions.

  12. Coordination of division and development influences complex multicellular behavior in Agrobacterium tumefaciens.

    Science.gov (United States)

    Kim, Jinwoo; Heindl, Jason E; Fuqua, Clay

    2013-01-01

    The α-Proteobacterium Agrobacterium tumefaciens has proteins homologous to known regulators that govern cell division and development in Caulobacter crescentus, many of which are also conserved among diverse α-Proteobacteria. In light of recent work demonstrating similarity between the division cycle of C. crescentus and that of A. tumefaciens, the functional conservation for this presumptive control pathway was examined. In C. crescentus the CtrA response regulator serves as the master regulator of cell cycle progression and cell division. CtrA activity is controlled by an integrated pair of multi-component phosphorelays: PleC/DivJ-DivK and CckA-ChpT-CtrA. Although several of the conserved orthologues appear to be essential in A. tumefaciens, deletions in pleC or divK were isolated and resulted in cell division defects, diminished swimming motility, and a decrease in biofilm formation. A. tumefaciens also has two additional pleC/divJhomologue sensor kinases called pdhS1 and pdhS2, absent in C. crescentus. Deletion of pdhS1 phenocopied the ΔpleC and ΔdivK mutants. Cells lacking pdhS2 morphologically resembled wild-type bacteria, but were decreased in swimming motility and elevated for biofilm formation, suggesting that pdhS2 may serve to regulate the motile to non-motile switch in A. tumefaciens. Genetic analysis suggests that the PleC/DivJ-DivK and CckA-ChpT-CtrA phosphorelays in A. tumefaciens are vertically-integrated, as in C. crescentus. A gain-of-function mutation in CckA (Y674D) was identified as a spontaneous suppressor of the ΔpleC motility phenotype. Thus, although the core architecture of the A. tumefaciens pathway resembles that of C. crescentus there are specific differences including additional regulators, divergent pathway architecture, and distinct target functions.

  13. Bacterial cytoskeleton and implications for new antibiotic targets.

    Science.gov (United States)

    Wang, Huan; Xie, Longxiang; Luo, Hongping; Xie, Jianping

    2016-01-01

    Traditionally eukaryotes exclusive cytoskeleton has been found in bacteria and other prokaryotes. FtsZ, MreB and CreS are bacterial counterpart of eukaryotic tubulin, actin filaments and intermediate filaments, respectively. FtsZ can assemble to a Z-ring at the cell division site, regulate bacterial cell division; MreB can form helical structure, and involve in maintaining cell shape, regulating chromosome segregation; CreS, found in Caulobacter crescentus (C. crescentus), can form curve or helical filaments in intracellular membrane. CreS is crucial for cell morphology maintenance. There are also some prokaryotic unique cytoskeleton components playing crucial roles in cell division, chromosome segregation and cell morphology. The cytoskeleton components of Mycobacterium tuberculosis (M. tuberculosis), together with their dynamics during exposure to antibiotics are summarized in this article to provide insights into the unique organization of this formidable pathogen and druggable targets for new antibiotics.

  14. New criteria for selecting the origin of DNA replication in Wolbachia and closely related bacteria

    DEFF Research Database (Denmark)

    Ioannidis, Panagiotis; Dunning Hotopp, Julie C; Sapountzis, Panagiotis

    2007-01-01

    as their patterns of sequence evolution will aid studies of cell replication and cell density, as well as the potential genetic manipulation of these widespread intracellular bacteria. RESULTS: Using features that have been previously experimentally verified in the alpha-Proteobacterium Caulobacter crescentus...... bacteria while fundamental characteristics like presence of DnaA and IHF binding sites as well as the boundary genes are more widely conserved. The relative paucity of CtrA binding sites in the ori regions, as well as the absence of key enzymes associated with DNA replication in the respective genomes...

  15. S-Layer Architectures: Extending the Morphogenetic Potential of S-Layer Protein Self Assembly

    Science.gov (United States)

    2012-07-11

    are   unilamellar   as  we   expected  due   to   the   extrusion  process.  Despite   the   long   incubation  with...of   the   point   of   zero   charge,   multilayer   island   structures  were  found.     38   9.2 Structural   Control

  16. S-Layer Based Bio-Imprinting - Synthetic S-Layer Polymers

    Science.gov (United States)

    2015-07-09

    Crystal  Microbalance  ( QCM )  studies...higher   compared  to  that  of  the  polymer.   Quartz  crystal  microbalance  ( QCM )  and  Surface  Plasmon  Resonance...as   determined   by   Quartz   Crystal   Microbalance   ( QCM )   measurements.   In   the   following,   one   electrode

  17. Physical and genetic characterization of an outer-membrane protein (OmpM1) containing an N-terminal S-layer-like homology domain from the phylogenetically Gram-positive gut anaerobe Mitsuokella multacida.

    Science.gov (United States)

    Kalmokoff, M L; Austin, J W; Cyr, T D; Hefford, M A; Teather, R M; Selinger, L B

    2009-06-01

    Thin sectioning and freeze-fracture-etch of the ovine ruminal isolate Mitsuokella multacida strain 46/5(2) revealed a Gram-negative envelope ultra-structure consisting of a peptidoglycan wall overlaid by an outer membrane. Sodium-dodecyl-sulfate-polyacrylamide gel electrophoretic (SDS-PAGE) analysis of whole cells, cell envelopes and Triton X-100 extracted envelopes in combination with thin-section and N-terminal sequence analyses demonstrated that the outer membrane contained two major proteins (45 and 43 kDa) sharing identical N-termini (A-A-N-P-F-S-D-V-P-A-D-H-W-A-Y-D). A gene encoding a protein with a predicted N-terminus identical to those of the 43 and 45 kDa outer-membrane proteins was cloned. The 1290 bp open reading frame encoded a 430 amino acid polypeptide with a predicted molecular mass of 47,492 Da. Cleavage of a predicted 23 amino acid leader sequence would yield a protein with a molecular mass of 45,232 Da. Mass spectroscopic analysis confirmed that the cloned gene (ompM1) encoded the 45 kDa outer-membrane protein. The N-terminus of the mature OmpM1 protein (residues 24-70) shared homology with surface-layer homology (SLH) domains found in a wide variety of regularly structured surface-layers (S-layers). However, the outer-membrane locale, resistance to denaturation by SDS and high temperatures and the finding that the C-terminal residue was a phenylalanine suggested that ompM1 encoded a porin. Threading analysis in combination with the identification of membrane spanning domains indicated that the C-terminal region of OmpM1 (residues 250-430) likely forms a 16-strand beta-barrel and appears to be related to the unusual N-terminal SLH-domain-containing beta-barrel-porins previously described in the cyanobacterium Synechococcus PCC6301.

  18. Polar Organizing Protein PopZ Is Required for Chromosome Segregation in Agrobacterium tumefaciens.

    Science.gov (United States)

    Ehrle, Haley M; Guidry, Jacob T; Iacovetto, Rebecca; Salisbury, Anne K; Sandidge, D J; Bowman, Grant R

    2017-09-01

    Despite being perceived as relatively simple organisms, many bacteria exhibit an impressive degree of subcellular organization. In Caulobacter crescentus , the evolutionarily conserved polar organizing protein PopZ facilitates cytoplasmic organization by recruiting chromosome centromeres and regulatory proteins to the cell poles. Here, we characterize the localization and function of PopZ in Agrobacterium tumefaciens , a genetically related species with distinct anatomy. In this species, we find that PopZ molecules are relocated from the old pole to the new pole in the minutes following cell division. PopZ is not required for the localization of the histidine kinases DivJ and PdhS1, which become localized to the old pole after PopZ relocation is complete. The histidine kinase PdhS2 is temporally and spatially related to PopZ in that it localizes to transitional poles just before they begin to shed PopZ and disappears from the old pole after PopZ relocalization. At the new pole, PopZ is required for tethering the centromere of at least one of multiple replicons (chromosome I), and the loss of popZ results in a severe chromosome segregation defect, aberrant cell division, and cell mortality. After cell division, the daughter that inherits polar PopZ is shorter in length and delayed in chromosome I segregation compared to its sibling. In this cell type, PopZ completes polar relocation well before the onset of chromosome segregation. While A. tumefaciens PopZ resembles its C. crescentus homolog in chromosome tethering activity, other aspects of its localization and function indicate distinct properties related to differences in cell organization. IMPORTANCE Members of the Alphaproteobacteria exhibit a wide range of phenotypic diversity despite sharing many conserved genes. In recent years, the extent to which this diversity is reflected at the level of subcellular organization has become increasingly apparent. However, which factors control such organization and how

  19. Complete genome of Phenylobacterium zucineum – a novel facultative intracellular bacterium isolated from human erythroleukemia cell line K562

    Directory of Open Access Journals (Sweden)

    Sun Jie

    2008-08-01

    Full Text Available Abstract Background Phenylobacterium zucineum is a recently identified facultative intracellular species isolated from the human leukemia cell line K562. Unlike the known intracellular pathogens, P. zucineum maintains a stable association with its host cell without affecting the growth and morphology of the latter. Results Here, we report the whole genome sequence of the type strain HLK1T. The genome consists of a circular chromosome (3,996,255 bp and a circular plasmid (382,976 bp. It encodes 3,861 putative proteins, 42 tRNAs, and a 16S-23S-5S rRNA operon. Comparative genomic analysis revealed that it is phylogenetically closest to Caulobacter crescentus, a model species for cell cycle research. Notably, P. zucineum has a gene that is strikingly similar, both structurally and functionally, to the cell cycle master regulator CtrA of C. crescentus, and most of the genes directly regulated by CtrA in the latter have orthologs in the former. Conclusion This work presents the first complete bacterial genome in the genus Phenylobacterium. Comparative genomic analysis indicated that the CtrA regulon is well conserved between C. crescentus and P. zucineum.

  20. A genomically modified Escherichia coli strain carrying an orthogonal E. coli histidyl-tRNA synthetase•tRNAHis pair.

    Science.gov (United States)

    Englert, Markus; Vargas-Rodriguez, Oscar; Reynolds, Noah M; Wang, Yane-Shih; Söll, Dieter; Umehara, Takuya

    2017-11-01

    Development of new aminoacyl-tRNA synthetase (aaRS)•tRNA pairs is central for incorporation of novel non-canonical amino acids (ncAAs) into proteins via genetic code expansion (GCE). The Escherichia coli and Caulobacter crescentus histidyl-tRNA synthetases (HisRS) evolved divergent mechanisms of tRNA His recognition that prevent their cross-reactivity. Although the E. coli HisRS•tRNA His pair is a good candidate for GCE, its use in C. crescentus is limited by the lack of established genetic selection methods and by the low transformation efficiency of C. crescentus. E. coli was genetically engineered to use a C. crescentus HisRS•tRNA His pair. Super-folder green fluorescent protein (sfGFP) and chloramphenicol acetyltransferase (CAT) were used as reporters for read-through assays. A library of 313 ncAAs coupled with the sfGFP reporter system was employed to investigate the specificity of E. coli HisRS in vivo. A genomically modified E. coli strain (named MEOV1) was created. MEVO1 requires an active C. crescentus HisRS•tRNA His pair for growth, and displays a similar doubling time as the parental E. coli strain. sfGFP- and CAT-based assays showed that the E. coli HisRS•tRNA His pair is orthogonal in MEOV1 cells. A mutation in the anticodon loop of E. coli tRNA His CUA elevated its suppression efficiency by 2-fold. The C. crescentus HisRS•tRNA His pair functionally complements an E. coli ΔhisS strain. The E. coli HisRS•tRNA His is orthogonal in MEOV1 cells. E. coli tRNA His CUA is an efficient amber suppressor in MEOV1. We developed a platform that allows protein engineering of E. coli HisRS that should facilitate GCE in E. coli. This article is part of a Special Issue entitled "Biochemistry of Synthetic Biology - Recent Developments" Guest Editor: Dr. Ilka Heinemann and Dr. Patrick O'Donoghue. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. The diversity and evolution of cell cycle regulation in alpha-proteobacteria: a comparative genomic analysis

    Directory of Open Access Journals (Sweden)

    Mengoni Alessio

    2010-04-01

    Full Text Available Abstract Background In the bacterium Caulobacter crescentus, CtrA coordinates DNA replication, cell division, and polar morphogenesis and is considered the cell cycle master regulator. CtrA activity varies during cell cycle progression and is modulated by phosphorylation, proteolysis and transcriptional control. In a phosphorylated state, CtrA binds specific DNA sequences, regulates the expression of genes involved in cell cycle progression and silences the origin of replication. Although the circuitry regulating CtrA is known in molecular detail in Caulobacter, its conservation and functionality in the other alpha-proteobacteria are still poorly understood. Results Orthologs of Caulobacter factors involved in the regulation of CtrA were systematically scanned in genomes of alpha-proteobacteria. In particular, orthologous genes of the divL-cckA-chpT-ctrA phosphorelay, the divJ-pleC-divK two-component system, the cpdR-rcdA-clpPX proteolysis system, the methyltransferase ccrM and transcriptional regulators dnaA and gcrA were identified in representative genomes of alpha-proteobacteria. CtrA, DnaA and GcrA binding sites and CcrM putative methylation sites were predicted in promoter regions of all these factors and functions controlled by CtrA in all alphas were predicted. Conclusions The regulatory cell cycle architecture was identified in all representative alpha-proteobacteria, revealing a high diversification of circuits but also a conservation of logical features. An evolutionary model was proposed where ancient alphas already possessed all modules found in Caulobacter arranged in a variety of connections. Two schemes appeared to evolve: a complex circuit in Caulobacterales and Rhizobiales and a simpler one found in Rhodobacterales.

  2. Second messenger-mediated tactile response by a bacterial rotary motor.

    Science.gov (United States)

    Hug, Isabelle; Deshpande, Siddharth; Sprecher, Kathrin S; Pfohl, Thomas; Jenal, Urs

    2017-10-27

    When bacteria encounter surfaces, they respond with surface colonization and virulence induction. The mechanisms of bacterial mechanosensation and downstream signaling remain poorly understood. Here, we describe a tactile sensing cascade in Caulobacter crescentus in which the flagellar motor acts as sensor. Surface-induced motor interference stimulated the production of the second messenger cyclic diguanylate by the motor-associated diguanylate cyclase DgcB. This led to the allosteric activation of the glycosyltransferase HfsJ to promote rapid synthesis of a polysaccharide adhesin and surface anchoring. Although the membrane-embedded motor unit was essential for surface sensing, mutants that lack external flagellar structures were hypersensitive to mechanical stimuli. Thus, the bacterial flagellar motor acts as a tetherless sensor reminiscent of mechanosensitive channels. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  3. Bacterial cell curvature through mechanical control of cell growth

    DEFF Research Database (Denmark)

    Cabeen, M.; Charbon, Godefroid; Vollmer, W.

    2009-01-01

    The cytoskeleton is a key regulator of cell morphogenesis. Crescentin, a bacterial intermediate filament-like protein, is required for the curved shape of Caulobacter crescentus and localizes to the inner cell curvature. Here, we show that crescentin forms a single filamentous structure...... that collapses into a helix when detached from the cell membrane, suggesting that it is normally maintained in a stretched configuration. Crescentin causes an elongation rate gradient around the circumference of the sidewall, creating a longitudinal cell length differential and hence curvature. Such curvature...... can be produced by physical force alone when cells are grown in circular microchambers. Production of crescentin in Escherichia coli is sufficient to generate cell curvature. Our data argue for a model in which physical strain borne by the crescentin structure anisotropically alters the kinetics...

  4. Origin of spatial organization of DNA-polymer in bacterial chromosomes

    Science.gov (United States)

    Agarwal, Tejal; Manjunath, G. P.; Habib, Farhat; Chatterji, Apratim

    2018-01-01

    In vivo DNA organization at large length scales (∼100 \\text{nm}) is highly debated and polymer models have proved useful to understand the principles of DNA organization. Here, we show that extracted from contact maps of bacterial DNA. We are able to predict the structure of 2 DNAs (E. coli and Caulobacter crescentus) using Monte Carlo simulations of the bead-spring polymer with cross-links at these special positions. Simulations with cross-links at random positions along the chain show that the organization of the polymer is different in nature from the previous case. We provide some direct and some indirect experimental validation for our predicted organization of DNA-polymers.

  5. Brucella abortus Cell Cycle and Infection Are Coordinated.

    Science.gov (United States)

    De Bolle, Xavier; Crosson, Sean; Matroule, Jean-Yves; Letesson, Jean-Jacques

    2015-12-01

    Brucellae are facultative intracellular pathogens. The recent development of methods and genetically engineered strains allowed the description of cell-cycle progression of Brucella abortus, including unipolar growth and the ordered initiation of chromosomal replication. B. abortus cell-cycle progression is coordinated with intracellular trafficking in the endosomal compartments. Bacteria are first blocked at the G1 stage, growth and chromosome replication being resumed shortly before reaching the intracellular proliferation compartment. The control mechanisms of cell cycle are similar to those reported for the bacterium Caulobacter crescentus, and they are crucial for survival in the host cell. The development of single-cell analyses could also be applied to other bacterial pathogens to investigate their cell-cycle progression during infection. Copyright © 2015 Elsevier Ltd. All rights reserved.

  6. The morphogenetic MreBCD proteins of Escherichia coli form an essential membrane-bound complex

    DEFF Research Database (Denmark)

    Kruse, Torben; Bork-Jensen, J.; Gerdes, Kenn

    2005-01-01

    . subtilis and C. crescentus, the mreB gene is essential. However, in E. coli, mreB was inferred not to be essential. Using a tight, conditional gene depletion system, we systematically investigated whether the E. coli mreBCD-encoded components were essential. We found that cells depleted of mreBCD became......D. In contrast, MreB and MreD did not interact in this assay. Thus, we conclude that the E. coli MreBCD form an essential membrane-bound complex. Curiously, MreB did not form cables in cell depleted for MreC, MreD or RodA, indicating a mutual interdependency between MreB filament morphology and cell shape. Based......MreB proteins of Escherichia coli, Bacillus subtilis and Caulobacter crescentus form actin-like cables lying beneath the cell surface. The cables are required to guide longitudinal cell wall synthesis and their absence leads to merodiploid spherical and inflated cells prone to cell lysis. In B...

  7. The CckA-ChpT-CtrA phosphorelay system is regulated by quorum sensing and controls flagellar motility in the marine sponge symbiont Ruegeria sp. KLH11.

    Directory of Open Access Journals (Sweden)

    Jindong Zan

    Full Text Available Bacteria respond to their environment via signal transduction pathways, often two-component type systems that function through phosphotransfer to control expression of specific genes. Phosphorelays are derived from two-component systems but are comprised of additional components. The essential cckA-chpT-ctrA phosphorelay in Caulobacter crescentus has been well studied and is important in orchestrating the cell cycle, polar development and flagellar biogenesis. Although cckA, chpT and ctrA homologues are widespread among the Alphaproteobacteria, relatively few is known about their function in the large and ecologically significant Roseobacter clade of the Rhodobacterales. In this study the cckA-chpT-ctrA system of the marine sponge symbiont Ruegeria sp. KLH11 was investigated. Our results reveal that the cckA, chpT and ctrA genes positively control flagellar biosynthesis. In contrast to C. crescentus, the cckA, chpT and ctrA genes in Ruegeria sp. KLH11 are non-essential and do not affect bacterial growth. Gene fusion and transcript analyses provide evidence for ctrA autoregulation and the control of motility-related genes. In KLH11, flagellar motility is controlled by the SsaRI system and acylhomoserine lactone (AHL quorum sensing. SsaR and long chain AHLs are required for cckA, chpT and ctrA gene expression, providing a regulatory link between flagellar locomotion and population density in KLH11.

  8. Co-ordinate synthesis and protein localization in a bacterial organelle by the action of a penicillin-binding-protein.

    Science.gov (United States)

    Hughes, H Velocity; Lisher, John P; Hardy, Gail G; Kysela, David T; Arnold, Randy J; Giedroc, David P; Brun, Yves V

    2013-12-01

    Organelles with specialized form and function occur in diverse bacteria. Within the Alphaproteobacteria, several species extrude thin cellular appendages known as stalks, which function in nutrient uptake, buoyancy and reproduction. Consistent with their specialization, stalks maintain a unique molecular composition compared with the cell body, but how this is achieved remains to be fully elucidated. Here we dissect the mechanism of localization of StpX, a stalk-specific protein in Caulobacter crescentus. Using a forward genetics approach, we identify a penicillin-binding-protein, PbpC, which is required for the localization of StpX in the stalk. We show that PbpC acts at the stalked cell pole to anchor StpX to rigid components of the outer membrane of the elongating stalk, concurrent with stalk synthesis. Stalk-localized StpX in turn functions in cellular responses to copper and zinc, suggesting that the stalk may contribute to metal homeostasis in Caulobacter. Together, these results identify a novel role for a penicillin-binding-protein in compartmentalizing a bacterial organelle it itself helps create, raising the possibility that cell wall-synthetic enzymes may broadly serve not only to synthesize the diverse shapes of bacteria, but also to functionalize them at the molecular level. © 2013 John Wiley & Sons Ltd.

  9. myo-Inositol and d-Ribose Ligand Discrimination in an ABC Periplasmic Binding Protein

    Science.gov (United States)

    Herrou, Julien

    2013-01-01

    The periplasmic binding protein (PBP) IbpA mediates the uptake of myo-inositol by the IatP-IatA ATP-binding cassette transmembrane transporter. We report a crystal structure of Caulobacter crescentus IbpA bound to myo-inositol at 1.45 Å resolution. This constitutes the first structure of a PBP bound to inositol. IbpA adopts a type I PBP fold consisting of two α-β lobes that surround a central hinge. A pocket positioned between the lobes contains the myo-inositol ligand, which binds with submicromolar affinity (0.76 ± 0.08 μM). IbpA is homologous to ribose-binding proteins and binds d-ribose with low affinity (50.8 ± 3.4 μM). On the basis of IbpA and ribose-binding protein structures, we have designed variants of IbpA with inverted binding specificity for myo-inositol and d-ribose. Five mutations in the ligand-binding pocket are sufficient to increase the affinity of IbpA for d-ribose by 10-fold while completely abolishing binding to myo-inositol. Replacement of ibpA with these mutant alleles unable to bind myo-inositol abolishes C. crescentus growth in medium containing myo-inositol as the sole carbon source. Neither deletion of ibpA nor replacement of ibpA with the high-affinity ribose binding allele affected C. crescentus growth on d-ribose as a carbon source, providing evidence that the IatP-IatA transporter is specific for myo-inositol. This study outlines the evolutionary relationship between ribose- and inositol-binding proteins and provides insight into the molecular basis upon which these two related, but functionally distinct, classes of periplasmic proteins specifically bind carbohydrate ligands. PMID:23504019

  10. A Localized Complex of Two Protein Oligomers Controls the Orientation of Cell Polarity

    Directory of Open Access Journals (Sweden)

    Adam M. Perez

    2017-02-01

    Full Text Available Signaling hubs at bacterial cell poles establish cell polarity in the absence of membrane-bound compartments. In the asymmetrically dividing bacterium Caulobacter crescentus, cell polarity stems from the cell cycle-regulated localization and turnover of signaling protein complexes in these hubs, and yet the mechanisms that establish the identity of the two cell poles have not been established. Here, we recapitulate the tripartite assembly of a cell fate signaling complex that forms during the G1-S transition. Using in vivo and in vitro analyses of dynamic polar protein complex formation, we show that a polymeric cell polarity protein, SpmX, serves as a direct bridge between the PopZ polymeric network and the cell fate-directing DivJ histidine kinase. We demonstrate the direct binding between these three proteins and show that a polar microdomain spontaneously assembles when the three proteins are coexpressed heterologously in an Escherichia coli test system. The relative copy numbers of these proteins are essential for complex formation, as overexpression of SpmX in Caulobacter reorganizes the polarity of the cell, generating ectopic cell poles containing PopZ and DivJ. Hierarchical formation of higher-order SpmX oligomers nucleates new PopZ microdomain assemblies at the incipient lateral cell poles, driving localized outgrowth. By comparison to self-assembling protein networks and polar cell growth mechanisms in other bacterial species, we suggest that the cooligomeric PopZ-SpmX protein complex in Caulobacter illustrates a paradigm for coupling cell cycle progression to the controlled geometry of cell pole establishment.

  11. A novel aldose-aldose oxidoreductase for co-production of D-xylonate and xylitol from D-xylose with Saccharomyces cerevisiae.

    Science.gov (United States)

    Wiebe, Marilyn G; Nygård, Yvonne; Oja, Merja; Andberg, Martina; Ruohonen, Laura; Koivula, Anu; Penttilä, Merja; Toivari, Mervi

    2015-11-01

    An open reading frame CC1225 from the Caulobacter crescentus CB15 genome sequence belongs to the Gfo/Idh/MocA protein family and has 47 % amino acid sequence identity with the glucose-fructose oxidoreductase from Zymomonas mobilis (Zm GFOR). We expressed the ORF CC1225 in the yeast Saccharomyces cerevisiae and used a yeast strain expressing the gene coding for Zm GFOR as a reference. Cell extracts of strains overexpressing CC1225 (renamed as Cc aaor) showed some Zm GFOR type of activity, producing D-gluconate and D-sorbitol when a mixture of D-glucose and D-fructose was used as substrate. However, the activity in Cc aaor expressing strain was >100-fold lower compared to strains expressing Zm gfor. Interestingly, C. crescentus AAOR was clearly more efficient than the Zm GFOR in converting in vitro a single sugar substrate D-xylose (10 mM) to xylitol without an added cofactor, whereas this type of activity was very low with Zm GFOR. Furthermore, when cultured in the presence of D-xylose, the S. cerevisiae strain expressing Cc aaor produced nearly equal concentrations of D-xylonate and xylitol (12.5 g D-xylonate l(-1) and 11.5 g D-xylitol l(-1) from 26 g D-xylose l(-1)), whereas the control strain and strain expressing Zm gfor produced only D-xylitol (5 g l(-1)). Deletion of the gene encoding the major aldose reductase, Gre3p, did not affect xylitol production in the strain expressing Cc aaor, but decreased xylitol production in the strain expressing Zm gfor. In addition, expression of Cc aaor together with the D-xylonolactone lactonase encoding the gene xylC from C. crescentus slightly increased the final concentration and initial volumetric production rate of both D-xylonate and D-xylitol. These results suggest that C. crescentus AAOR is a novel type of oxidoreductase able to convert the single aldose substrate D-xylose to both its oxidized and reduced product.

  12. Characterization of porcine-specific surface (S-) layer protein carrying Lactobacillus species, S-layer proteins and the adhesin of Escherichia coli F18 fimbriae

    OpenAIRE

    Jakava-Viljanen, Miia

    2007-01-01

    Pigs coexist with diverse and dense commensal microbiota in their gastrointestinal tract (GIT). Lactobacilli, identified as common members of porcine intestinal microbiota, have been considered to be an important group of bacteria in maintaining the stability of GIT, in preventing intestinal infections and generally, in supporting intestinal health. Because several species of lactobacilli have GRAS (generally regarded as safe) status and some of them have an ability to interact with intestina...

  13. Mathematical modeling of bacterial track-altering motors: Track cleaving through burnt-bridge ratchets.

    Science.gov (United States)

    Shtylla, Blerta; Keener, James P

    2015-04-01

    The generation of directed movement of cellular components frequently requires the rectification of Brownian motion. Molecular motor enzymes that use ATP to walk on filamentous tracks are typically involved in cell transport, however, a track-altering motor can arise when an enzyme interacts with and alters its track. In Caulobacter crescentus and other bacteria, an active DNA partitioning (Par) apparatus is employed to segregate replicated chromosome regions to specific locations in dividing cells. The Par apparatus is composed of two proteins: ParA, an ATPase that can form polymeric structures on the nucleoid, and ParB, a protein that can bind and destabilize ParA structures. It has been proposed that the ParB-mediated alteration of ParA structures could be responsible for generating the directed movement of DNA during bacterial division. How precisely these actions are coordinated and translated into directed movement is not clear. In this paper we consider the C. crescentus segregation apparatus as an example of a track altering motor that operates using a so-called burnt-bridge mechanism. We develop and analyze mathematical models that examine how diffusion and ATP-hydrolysis-mediated monomer removal (or cleaving) can be combined to generate directed movement. Using a mean first passage approach, we analytically calculate the effective ParA track-cleaving velocities, effective diffusion coefficient, and other higher moments for the movement a ParB protein cluster that breaks monomers away at random locations on a single ParA track. Our model results indicate that cleaving velocities and effective diffusion constants are sensitive to ParB-induced ATP hydrolysis rates. Our analytical results are in excellent agreement with stochastic simulation results.

  14. Defect characterization of Ga4Se3S layered single crystals by ...

    Indian Academy of Sciences (India)

    from 27 to 40 meV by rising the stopping temperature from 15 to 36 K. Keywords. Thermoluminescence; semiconductors; defects. PACS Nos 71.20.Nr; 71.55.−i; 78.60.Kn. 1. Introduction. GaSe and GaS belonging to III–VI group of semiconducting compounds are effective materials to be used in optoelectronic devices in red ...

  15. Defect characterization of Ga4Se3S layered single crystals by ...

    Indian Academy of Sciences (India)

    Experimental details. Ga4Se3S polycrystals were synthesized from high-purity elements prepared in stoi- chiometric proportions.Gallium (Aldrich cat. no. 263273), selenium (Aldrich cat.no. 204307) and sulphur (Fluka cat. no. 84680) were of 99.999% purity. Ga4Se3S single crystals were grown by Bridgman method from the ...

  16. Defect characterization of Ga4Se3S layered single crystals by ...

    Indian Academy of Sciences (India)

    Author Affiliations. Isik M1 Delice S2 Gasanly N2 3. Department of Electrical and Electronics Engineering, Atilim University, 06836 Ankara, Turkey; Department of Physics, Middle East Technical University, 06800 Ankara, Turkey; Virtual International Scientific Research Centre, Baku State University, 1148 Baku, Azerbaijan ...

  17. Two-Dimensional SiS Layers with Promising Electronic and Optoelectronic Properties: Theoretical Prediction.

    Science.gov (United States)

    Yang, Ji-Hui; Zhang, Yueyu; Yin, Wan-Jian; Gong, X G; Yakobson, Boris I; Wei, Su-Huai

    2016-02-10

    Two-dimensional (2D) semiconductors can be very useful for novel electronic and optoelectronic applications because of their good material properties. However, all current 2D materials have shortcomings that limit their performance. As a result, new 2D materials are highly desirable. Using atomic transmutation and differential evolution global optimization methods, we identified two group IV-VI 2D materials, Pma2-SiS and silicene sulfide. Pma2-SiS is found to be both chemically, energetically, and thermally stable. Most importantly, Pma2-SiS has shown good electronic and optoelectronic properties, including direct bandgaps suitable for solar cells, good mobility for nanoelectronics, good flexibility of property tuning by layer control and applied strain, and good air stability as well. Therefore, Pma2-SiS is expected to be a promising 2D material in the field of 2D electronics and optoelectronics. The designing principles demonstrated in identifying these two tantalizing examples have great potential to accelerate the finding of new functional 2D materials.

  18. Defect characterization of Ga4Se3S layered single crystals by ...

    Indian Academy of Sciences (India)

    Trapping centres in undoped Ga 4 Se 3 S single crystals grown by Bridgman method were characterized for the first time by thermoluminescence (TL) measurements carried out in the low temperature range of 15−300 K. After illuminating the sample with blue light (∼470 nm) at 15 K, TL glow curve exhibited one peak ...

  19. Magnetic Au Nanoparticles on Archaeal S-Layer Ghosts as Templates

    Directory of Open Access Journals (Sweden)

    Sonja Selenska-Pobell

    2011-10-01

    Full Text Available Cell‐ghosts representing empty cells of the archaeon Sulfolobus acidocaldarius, consisting only of their highly ordered and unusually stable outermost proteinaceous surface layer (S‐layer, were used as templates for Au nanoparticles fabrication. The properties of these archaeal Au nanoparticles differ significantly from those produced earlier by us onto bacterial S‐layer sheets. The archaeal Au nanoparticles, with a size of about 2.5 nm, consist exclusively of metallic Au(0, while those produced on the bacterial S‐layer had a size of about 4 nm and represented a mixture of Au(0 and Au(III in the ratio of 40 to 60 %. The most impressive feature of the archaeal Au nanoparticles is that they are strongly paramagnetic, in contrast to the bacterial ones and also to bulk gold. SQUID magnetometry and XMCD measurements demonstrated that the archaeal Au nanoparticles possess a rather large magnetic moment of about 0.1 µB/atom. HR‐ TEM‐EDX analysis revealed that the archaeal Au nanoparticles are linked to the sulfur atoms of the thiol groups of the amino acid cysteine, characteristic only for archaeal S‐layers. This is the first study demonstrating the formation of such unusually strong magnetic Au nanoparticles on a non‐modified archaeal S‐layer.

  20. Structure of a putative trans-editing enzyme for prolyl-tRNA synthetase from Aeropyrum pernix K1 at 1.7 Å resolution

    Energy Technology Data Exchange (ETDEWEB)

    Murayama, Kazutaka; Kato-Murayama, Miyuki; Katsura, Kazushige; Uchikubo-Kamo, Tomomi; Yamaguchi-Hirafuji, Machiko; Kawazoe, Masahito; Akasaka, Ryogo; Hanawa-Suetsugu, Kyoko; Hori-Takemoto, Chie [RIKEN Genomic Sciences Center, Yokohama (Japan); Terada, Takaho [RIKEN Genomic Sciences Center, Yokohama (Japan); RIKEN Harima Institute at SPring-8, Hyogo (Japan); Shirouzu, Mikako [RIKEN Harima Institute at SPring-8, Hyogo (Japan); Yokoyama, Shigeyuki, E-mail: yokoyama@biochem.s.u-tokyo.ac.jp [RIKEN Genomic Sciences Center, Yokohama (Japan); RIKEN Harima Institute at SPring-8, Hyogo (Japan); Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Tokyo (Japan)

    2005-01-01

    The three-dimensional structure of the APE2540 protein from A. pernix K1 has been determined by the multiple anomalous dispersion method at 1.7 Å resolution. The structure includes two monomers in the asymmetric unit and shares structural similarity with the YbaK protein or cysteinyl-tRNA{sup Pro} deacylase from H. influenzae. The crystal structure of APE2540, the putative trans-editing enzyme ProX from Aeropyrum pernix K1, was determined in a high-throughput manner. The crystal belongs to the monoclinic space group P2{sub 1}, with unit-cell parameters a = 47.4, b = 58.9, c = 53.6 Å, β = 106.8°. The structure was solved by the multiwavelength anomalous dispersion method at 1.7 Å and refined to an R factor of 16.8% (R{sub free} = 20.5%). The crystal structure includes two protein molecules in the asymmetric unit. Each monomer consists of eight β-strands and seven α-helices. A structure-homology search revealed similarity between the trans-editing enzyme YbaK (or cysteinyl-tRNA{sup Pro} deacylase) from Haemophilus influenzae (HI1434; 22% sequence identity) and putative ProX proteins from Caulobacter crescentus (16%) and Agrobacterium tumefaciens (21%)

  1. Surface contact stimulates the just-in-time deployment of bacterial adhesins.

    Science.gov (United States)

    Li, Guanglai; Brown, Pamela J B; Tang, Jay X; Xu, Jing; Quardokus, Ellen M; Fuqua, Clay; Brun, Yves V

    2012-01-01

    The attachment of bacteria to surfaces provides advantages such as increasing nutrient access and resistance to environmental stress. Attachment begins with a reversible phase, often mediated by surface structures such as flagella and pili, followed by a transition to irreversible attachment, typically mediated by polysaccharides. Here we show that the interplay between pili and flagellum rotation stimulates the rapid transition between reversible and polysaccharide-mediated irreversible attachment. We found that reversible attachment of Caulobacter crescentus cells is mediated by motile cells bearing pili and that their contact with a surface results in the rapid pili-dependent arrest of flagellum rotation and concurrent stimulation of polar holdfast adhesive polysaccharide. Similar stimulation of polar adhesin production by surface contact occurs in Asticcacaulis biprosthecum and Agrobacterium tumefaciens. Therefore, single bacterial cells respond to their initial contact with surfaces by triggering just-in-time adhesin production. This mechanism restricts stable attachment to intimate surface interactions, thereby maximizing surface attachment, discouraging non-productive self-adherence, and preventing curing of the adhesive. © 2011 Blackwell Publishing Ltd.

  2. Analytical Validation of a New Enzymatic and Automatable Method for d-Xylose Measurement in Human Urine Samples

    Directory of Open Access Journals (Sweden)

    Israel Sánchez-Moreno

    2017-01-01

    Full Text Available Hypolactasia, or intestinal lactase deficiency, affects more than half of the world population. Currently, xylose quantification in urine after gaxilose oral administration for the noninvasive diagnosis of hypolactasia is performed with the hand-operated nonautomatable phloroglucinol reaction. This work demonstrates that a new enzymatic xylose quantification method, based on the activity of xylose dehydrogenase from Caulobacter crescentus, represents an excellent alternative to the manual phloroglucinol reaction. The new method is automatable and facilitates the use of the gaxilose test for hypolactasia diagnosis in the clinical practice. The analytical validation of the new technique was performed in three different autoanalyzers, using buffer or urine samples spiked with different xylose concentrations. For the comparison between the phloroglucinol and the enzymatic assays, 224 urine samples of patients to whom the gaxilose test had been prescribed were assayed by both methods. A mean bias of −16.08 mg of xylose was observed when comparing the results obtained by both techniques. After adjusting the cut-off of the enzymatic method to 19.18 mg of xylose, the Kappa coefficient was found to be 0.9531, indicating an excellent level of agreement between both analytical procedures. This new assay represents the first automatable enzymatic technique validated for xylose quantification in urine.

  3. Establishment of oxidative D-xylose metabolism in Pseudomonas putida S12.

    Science.gov (United States)

    Meijnen, Jean-Paul; de Winde, Johannes H; Ruijssenaars, Harald J

    2009-05-01

    The oxidative D-xylose catabolic pathway of Caulobacter crescentus, encoded by the xylXABCD operon, was expressed in the gram-negative bacterium Pseudomonas putida S12. This engineered transformant strain was able to grow on D-xylose as a sole carbon source with a biomass yield of 53% (based on g [dry weight] g D-xylose(-1)) and a maximum growth rate of 0.21 h(-1). Remarkably, most of the genes of the xylXABCD operon appeared to be dispensable for growth on D-xylose. Only the xylD gene, encoding D-xylonate dehydratase, proved to be essential for establishing an oxidative D-xylose catabolic pathway in P. putida S12. The growth performance on D-xylose was, however, greatly improved by coexpression of xylXA, encoding 2-keto-3-deoxy-D-xylonate dehydratase and alpha-ketoglutaric semialdehyde dehydrogenase, respectively. The endogenous periplasmic glucose dehydrogenase (Gcd) of P. putida S12 was found to play a key role in efficient oxidative D-xylose utilization. Gcd activity not only contributes to D-xylose oxidation but also prevents the intracellular accumulation of toxic catabolic intermediates which delays or even eliminates growth on D-xylose.

  4. The bacterial tubulin FtsZ requires its intrinsically disordered linker to direct robust cell wall construction.

    Science.gov (United States)

    Sundararajan, Kousik; Miguel, Amanda; Desmarais, Samantha M; Meier, Elizabeth L; Casey Huang, Kerwyn; Goley, Erin D

    2015-06-23

    The bacterial GTPase FtsZ forms a cytokinetic ring at midcell, recruits the division machinery and orchestrates membrane and peptidoglycan cell wall invagination. However, the mechanism for FtsZ regulation of peptidoglycan metabolism is unknown. The FtsZ GTPase domain is separated from its membrane-anchoring C-terminal conserved (CTC) peptide by a disordered C-terminal linker (CTL). Here we investigate CTL function in Caulobacter crescentus. Strikingly, production of FtsZ lacking the CTL (ΔCTL) is lethal: cells become filamentous, form envelope bulges and lyse, resembling treatment with β-lactam antibiotics. This phenotype is produced by FtsZ polymers bearing the CTC and a CTL shorter than 14 residues. Peptidoglycan synthesis still occurs downstream of ΔCTL; however, cells expressing ΔCTL exhibit reduced peptidoglycan crosslinking and longer glycan strands than wild type. Importantly, midcell proteins are still recruited to sites of ΔCTL assembly. We propose that FtsZ regulates peptidoglycan metabolism through a CTL-dependent mechanism that extends beyond simple protein recruitment.

  5. Large-scale chromosome folding versus genomic DNA sequences: A discrete double Fourier transform technique.

    Science.gov (United States)

    Chechetkin, V R; Lobzin, V V

    2017-08-07

    Using state-of-the-art techniques combining imaging methods and high-throughput genomic mapping tools leaded to the significant progress in detailing chromosome architecture of various organisms. However, a gap still remains between the rapidly growing structural data on the chromosome folding and the large-scale genome organization. Could a part of information on the chromosome folding be obtained directly from underlying genomic DNA sequences abundantly stored in the databanks? To answer this question, we developed an original discrete double Fourier transform (DDFT). DDFT serves for the detection of large-scale genome regularities associated with domains/units at the different levels of hierarchical chromosome folding. The method is versatile and can be applied to both genomic DNA sequences and corresponding physico-chemical parameters such as base-pairing free energy. The latter characteristic is closely related to the replication and transcription and can also be used for the assessment of temperature or supercoiling effects on the chromosome folding. We tested the method on the genome of E. coli K-12 and found good correspondence with the annotated domains/units established experimentally. As a brief illustration of further abilities of DDFT, the study of large-scale genome organization for bacteriophage PHIX174 and bacterium Caulobacter crescentus was also added. The combined experimental, modeling, and bioinformatic DDFT analysis should yield more complete knowledge on the chromosome architecture and genome organization. Copyright © 2017 Elsevier Ltd. All rights reserved.

  6. Structure of a putative trans-editing enzyme for prolyl-tRNA synthetase from Aeropyrum pernix K1 at 1.7 Å resolution

    International Nuclear Information System (INIS)

    Murayama, Kazutaka; Kato-Murayama, Miyuki; Katsura, Kazushige; Uchikubo-Kamo, Tomomi; Yamaguchi-Hirafuji, Machiko; Kawazoe, Masahito; Akasaka, Ryogo; Hanawa-Suetsugu, Kyoko; Hori-Takemoto, Chie; Terada, Takaho; Shirouzu, Mikako; Yokoyama, Shigeyuki

    2004-01-01

    The three-dimensional structure of the APE2540 protein from A. pernix K1 has been determined by the multiple anomalous dispersion method at 1.7 Å resolution. The structure includes two monomers in the asymmetric unit and shares structural similarity with the YbaK protein or cysteinyl-tRNA Pro deacylase from H. influenzae. The crystal structure of APE2540, the putative trans-editing enzyme ProX from Aeropyrum pernix K1, was determined in a high-throughput manner. The crystal belongs to the monoclinic space group P2 1 , with unit-cell parameters a = 47.4, b = 58.9, c = 53.6 Å, β = 106.8°. The structure was solved by the multiwavelength anomalous dispersion method at 1.7 Å and refined to an R factor of 16.8% (R free = 20.5%). The crystal structure includes two protein molecules in the asymmetric unit. Each monomer consists of eight β-strands and seven α-helices. A structure-homology search revealed similarity between the trans-editing enzyme YbaK (or cysteinyl-tRNA Pro deacylase) from Haemophilus influenzae (HI1434; 22% sequence identity) and putative ProX proteins from Caulobacter crescentus (16%) and Agrobacterium tumefaciens (21%)

  7. Intracellular chemical gradients: morphing principle in bacteria

    Directory of Open Access Journals (Sweden)

    Endres Robert G

    2012-09-01

    Full Text Available Abstract Advances in computational biology allow systematic investigations to ascertain whether internal chemical gradients can be maintained in bacteria – an open question at the resolution limit of fluorescence microscopy. While it was previously believed that the small bacterial cell size and fast diffusion in the cytoplasm effectively remove any such gradient, a new computational study published in BMC Biophysics supports the emerging view that gradients can exist. The study arose from the recent observation that phosphorylated CtrA forms a gradient prior to cell division in Caulobacter crescentus, a bacterium known for its complicated cell cycle. Tropini et al. (2012 postulate that such gradients can provide an internal chemical compass, directing protein localization, cell division and cell development. More specifically, they describe biochemical and physical constraints on the formation of such gradients and explore a number of existing bacterial cell morphologies. These chemical gradients may limit in vitro analyses, and may ensure timing control and robustness to fluctuations during critical stages in cell development.

  8. A novel roseobacter phage possesses features of podoviruses, siphoviruses, prophages and gene transfer agents

    Science.gov (United States)

    Zhan, Yuanchao; Huang, Sijun; Voget, Sonja; Simon, Meinhard; Chen, Feng

    2016-07-01

    Bacteria in the Roseobacter lineage have been studied extensively due to their significant biogeochemical roles in the marine ecosystem. However, our knowledge on bacteriophage which infects the Roseobacter clade is still very limited. Here, we report a new bacteriophage, phage DSS3Φ8, which infects marine roseobacter Ruegeria pomeroyi DSS-3. DSS3Φ8 is a lytic siphovirus. Genomic analysis showed that DSS3Φ8 is most closely related to a group of siphoviruses, CbK-like phages, which infect freshwater bacterium Caulobacter crescentus. DSS3Φ8 contains a smaller capsid and has a reduced genome size (146 kb) compared to the CbK-like phages (205-279 kb). DSS3Φ8 contains the DNA polymerase gene which is closely related to T7-like podoviruses. DSS3Φ8 also contains the integrase and repressor genes, indicating its potential to involve in lysogenic cycle. In addition, four GTA (gene transfer agent) genes were identified in the DSS3Φ8 genome. Genomic analysis suggests that DSS3Φ8 is a highly mosaic phage that inherits the genetic features from siphoviruses, podoviruses, prophages and GTAs. This is the first report of CbK-like phages infecting marine bacteria. We believe phage isolation is still a powerful tool that can lead to discovery of new phages and help interpret the overwhelming unknown sequences in the viral metagenomics.

  9. β-Helical architecture of cytoskeletal bactofilin filaments revealed by solid-state NMR

    Science.gov (United States)

    Vasa, Suresh; Lin, Lin; Shi, Chaowei; Habenstein, Birgit; Riedel, Dietmar; Kühn, Juliane; Thanbichler, Martin; Lange, Adam

    2015-01-01

    Bactofilins are a widespread class of bacterial filament-forming proteins, which serve as cytoskeletal scaffolds in various cellular pathways. They are characterized by a conserved architecture, featuring a central conserved domain (DUF583) that is flanked by variable terminal regions. Here, we present a detailed investigation of bactofilin filaments from Caulobacter crescentus by high-resolution solid-state NMR spectroscopy. De novo sequential resonance assignments were obtained for residues Ala39 to Phe137, spanning the conserved DUF583 domain. Analysis of the secondary chemical shifts shows that this core region adopts predominantly β-sheet secondary structure. Mutational studies of conserved hydrophobic residues located in the identified β-strand segments suggest that bactofilin folding and polymerization is mediated by an extensive and redundant network of hydrophobic interactions, consistent with the high intrinsic stability of bactofilin polymers. Transmission electron microscopy revealed a propensity of bactofilin to form filament bundles as well as sheet-like, 2D crystalline assemblies, which may represent the supramolecular arrangement of bactofilin in the native context. Based on the diffraction pattern of these 2D crystalline assemblies, scanning transmission electron microscopy measurements of the mass per length of BacA filaments, and the distribution of β-strand segments identified by solid-state NMR, we propose that the DUF583 domain adopts a β-helical architecture, in which 18 β-strand segments are arranged in six consecutive windings of a β-helix. PMID:25550503

  10. Active motility in bimodular bacterial aggregates

    Science.gov (United States)

    Zeng, Yu; Liu, Bin

    2017-11-01

    Dispersal capability is essential for microorganisms to achieve long-distance translocation, thus crucial for their abundance in various environments. In general, active dispersals are attributed to the movements of self-powered planktonic cells, while sessile cells that live a colonial life often disperse passively through flow entrainments. Here, we report another means of active dispersal employed by aggregates of sessile cells. The spherical rosette colonies of the bacterium Caulobacter crescentus are aggregates of sessile stalked cells, of which a small proportion undergo cell division, grow active flagella and effect whole-rosette motility. We show that these rosettes actively disperse both in bulk water and near the solid-liquid interface. In particular, the proximity of a self-powered rosette to the solid surface promotes a rolling movement, leading to its persistent transportation along the solid boundary. The active dispersal of these rosettes demonstrated a novel mode of colonial transportation that is based on the division of labor between sessile and motile cells. The authors thank the support of National Science Foundation CREST: Center for Cellular and Biomolecular Machines at UC Merced (NSF-HRD-1547848).

  11. Genome Partitioner: A web tool for multi-level partitioning of large-scale DNA constructs for synthetic biology applications.

    Directory of Open Access Journals (Sweden)

    Matthias Christen

    Full Text Available Recent advances in lower-cost DNA synthesis techniques have enabled new innovations in the field of synthetic biology. Still, efficient design and higher-order assembly of genome-scale DNA constructs remains a labor-intensive process. Given the complexity, computer assisted design tools that fragment large DNA sequences into fabricable DNA blocks are needed to pave the way towards streamlined assembly of biological systems. Here, we present the Genome Partitioner software implemented as a web-based interface that permits multi-level partitioning of genome-scale DNA designs. Without the need for specialized computing skills, biologists can submit their DNA designs to a fully automated pipeline that generates the optimal retrosynthetic route for higher-order DNA assembly. To test the algorithm, we partitioned a 783 kb Caulobacter crescentus genome design. We validated the partitioning strategy by assembling a 20 kb test segment encompassing a difficult to synthesize DNA sequence. Successful assembly from 1 kb subblocks into the 20 kb segment highlights the effectiveness of the Genome Partitioner for reducing synthesis costs and timelines for higher-order DNA assembly. The Genome Partitioner is broadly applicable to translate DNA designs into ready to order sequences that can be assembled with standardized protocols, thus offering new opportunities to harness the diversity of microbial genomes for synthetic biology applications. The Genome Partitioner web tool can be accessed at https://christenlab.ethz.ch/GenomePartitioner.

  12. Experimental evolution of aging in a bacterium

    Directory of Open Access Journals (Sweden)

    Stearns Stephen C

    2007-07-01

    Full Text Available Abstract Background Aging refers to a decline in reproduction and survival with increasing age. According to evolutionary theory, aging evolves because selection late in life is weak and mutations exist whose deleterious effects manifest only late in life. Whether the assumptions behind this theory are fulfilled in all organisms, and whether all organisms age, has not been clear. We tested the generality of this theory by experimental evolution with Caulobacter crescentus, a bacterium whose asymmetric division allows mother and daughter to be distinguished. Results We evolved three populations for 2000 generations in the laboratory under conditions where selection was strong early in life, but very weak later in life. All populations evolved faster growth rates, mostly by decreasing the age at first division. Evolutionary changes in aging were inconsistent. The predominant response was the unexpected evolution of slower aging, revealing the limits of theoretical predictions if mutations have unanticipated phenotypic effects. However, we also observed the spread of a mutation causing earlier aging of mothers whose negative effect was reset in the daughters. Conclusion Our results confirm that late-acting deleterious mutations do occur in bacteria and that they can invade populations when selection late in life is weak. They suggest that very few organisms – perhaps none- can avoid the accumulation of such mutations over evolutionary time, and thus that aging is probably a fundamental property of all cellular organisms.

  13. Aquatic bacteria elongate and wobble their bodies for flagellar performance

    Science.gov (United States)

    Liu, Bin; Valenzuela, Joanna; Chopra, Pooja

    2017-11-01

    Bacteria are endowed with well-regulated sizes and shapes. A bacillus has a rod-like cell body, achieving swimming motility by rotating a single flagellum or multiple flagella. Along with other shapes, this elongated cell is often viewed as a payload, and its movements are regarded as passive responses to its flagellar propulsion. Here, we simultaneously measured the morphology and movement of individual free-swimming bacteria using an automated tracking microscope and 3D reconstruction techniques. These cells were found to consistently precess, based on reconstructions of the apparent wobbling movements viewed from a microscope. Through a hydrodynamic model that incorporates such precessing cell bodies and rod-like geometries, we found that there is a critical cell size below which wobbling movement is beneficial for flagellar performance. This critical cell size is consistent with the cellular morphologies of Caulobacter crescentus and Escherichia coli, as examples of single- and multi-flagellated species that are known for wobbling movements in aquatic environments. We also showed that the moderate cell sizes of these species could be attributed to a compromise between dispersal speed and power consumption. The authors thank the support of NSF-CREST: Center for Cellular and Biomolecular Machines at UC Merced (NSF-HRD-1547848).

  14. Architecture and inherent robustness of a bacterial cell-cycle control system.

    Science.gov (United States)

    Shen, Xiling; Collier, Justine; Dill, David; Shapiro, Lucy; Horowitz, Mark; McAdams, Harley H

    2008-08-12

    A closed-loop control system drives progression of the coupled stalked and swarmer cell cycles of the bacterium Caulobacter crescentus in a near-mechanical step-like fashion. The cell-cycle control has a cyclical genetic circuit composed of four regulatory proteins with tight coupling to processive chromosome replication and cell division subsystems. We report a hybrid simulation of the coupled cell-cycle control system, including asymmetric cell division and responses to external starvation signals, that replicates mRNA and protein concentration patterns and is consistent with observed mutant phenotypes. An asynchronous sequential digital circuit model equivalent to the validated simulation model was created. Formal model-checking analysis of the digital circuit showed that the cell-cycle control is robust to intrinsic stochastic variations in reaction rates and nutrient supply, and that it reliably stops and restarts to accommodate nutrient starvation. Model checking also showed that mechanisms involving methylation-state changes in regulatory promoter regions during DNA replication increase the robustness of the cell-cycle control. The hybrid cell-cycle simulation implementation is inherently extensible and provides a promising approach for development of whole-cell behavioral models that can replicate the observed functionality of the cell and its responses to changing environmental conditions.

  15. Response of single bacterial cells to stress gives rise to complex history dependence at the population level

    Science.gov (United States)

    Mathis, Roland; Ackermann, Martin

    2016-01-01

    Most bacteria live in ever-changing environments where periods of stress are common. One fundamental question is whether individual bacterial cells have an increased tolerance to stress if they recently have been exposed to lower levels of the same stressor. To address this question, we worked with the bacterium Caulobacter crescentus and asked whether exposure to a moderate concentration of sodium chloride would affect survival during later exposure to a higher concentration. We found that the effects measured at the population level depended in a surprising and complex way on the time interval between the two exposure events: The effect of the first exposure on survival of the second exposure was positive for some time intervals but negative for others. We hypothesized that the complex pattern of history dependence at the population level was a consequence of the responses of individual cells to sodium chloride that we observed: (i) exposure to moderate concentrations of sodium chloride caused delays in cell division and led to cell-cycle synchronization, and (ii) whether a bacterium would survive subsequent exposure to higher concentrations was dependent on the cell-cycle state. Using computational modeling, we demonstrated that indeed the combination of these two effects could explain the complex patterns of history dependence observed at the population level. Our insight into how the behavior of single cells scales up to processes at the population level provides a perspective on how organisms operate in dynamic environments with fluctuating stress exposure. PMID:26960998

  16. The presence of two S-layer-protein-encoding genes is conserved among species related to Lactobacillus acidophilus

    NARCIS (Netherlands)

    Boot, H.J.; Kolen, C.P.A.M.; Pot, B.; Kersters, K.; Pouwels, P.H.

    1996-01-01

    Previously we have shown that the type strain of Lactobacillus acidophilus possesses two S-protein-encoding genes, one of which is silent, on a chromosomal segment of 6 kb. The S-protein-encoding gene in the expression site can be exchanged for the silent S-protein-encoding gene by inversion of this

  17. Small angle X-ray scattering and transmission electron microscopy study of the Lactobacillus brevis S-layer protein

    Energy Technology Data Exchange (ETDEWEB)

    Jaeaeskelaeinen, Pentti [Department of Biomedical Engineering and Computational Science, PO Box 2200, FI-02015 Aalto University School of Science and Technology (Finland); Engelhardt, Peter [Haartman Institute, Department of Pathology, PO Box 21, FIN-00014 University of Helsinki (Finland); Hynoenen, Ulla; Palva, Airi [Department of Basic Veterinary Sciences, Division of Microbiology, FIN-00014 University of Helsinki (Finland); Torkkeli, Mika; Serimaa, Ritva, E-mail: ritva.serimaa@helsinki.f [Department of Physics, POB 64, 00014 University of Helsinki (Finland)

    2010-10-01

    The structure of self-assembly domain containing recombinant truncation mutants of Lactobacillus brevis surface layer protein SlpA in aqueous solution was studied using small-angle X-ray scattering and transmission electron microscopy. The proteins were found out to interact with each other forming stable globular oligomers of about 10 monomers. The maximum diameter of the oligomers varied between 75 A and 435 A.

  18. Fast and easy protocol for the purification of recombinant S-layer protein for synthetic biology applications

    KAUST Repository

    Norville, Julie E.

    2011-06-17

    A goal of synthetic biology is to make biological systems easier to engineer. One of the aims is to design, with nanometer-scale precision, biomaterials with well-defined properties. The surface-layer protein SbpA forms 2D arrays naturally on the cell surface of Lysinibacillus sphaericus, but also as the purified protein in solution upon the addition of divalent cations. The high propensity of SbpA to form crystalline arrays, which can be simply controlled by divalent cations, and the possibility to genetically alter the protein, make SbpA an attractive molecule for synthetic biology. To be a useful tool, however, it is important that a simple protocol can be used to produce recombinant wild-type and modified SbpA in large quantities and in a biologically active form. The present study addresses this requirement by introducing a mild and non-denaturing purification protocol to produce milligram quantities of recombinant, active SbpA.

  19. Rapid Communication Fast and easy protocol for the purification of recombinant S-layer protein for synthetic biology applications

    Science.gov (United States)

    Norville, Julie E; Kelly, Deborah F; Knight, Thomas F; Belcher, Angela M; Walz, Thomas

    2015-01-01

    A goal of synthetic biology is to make biological systems easier to engineer. One of the aims is to design – with nanometer-scale precision – biomaterials with well-defined properties. The surface layer protein SbpA forms two-dimensional (2D) arrays naturally on the cell surface of Lysinibacillus sphaericus but also as purified protein in solution upon addition of divalent cations. Its high propensity to form crystalline arrays, the simple way by which its crystallization can be controlled by divalent cations and the possibility to genetically alter the protein make SbpA an attractive molecule for synthetic biology. To be a useful tool, however, it is important that a simple protocol can be used to produce recombinant wild-type as well as modified SbpA in large quantities and in a biologically active form. The present study addresses this requirement by introducing a mild and non-denaturing purification protocol to produce milligram quantities of recombinant, active SbpA. PMID:21681963

  20. Small angle X-ray scattering and transmission electron microscopy study of the Lactobacillus brevis S-layer protein

    Science.gov (United States)

    Jääskeläinen, Pentti; Engelhardt, Peter; Hynönen, Ulla; Torkkeli, Mika; Palva, Airi; Serimaa, Ritva

    2010-10-01

    The structure of self-assembly domain containing recombinant truncation mutants of Lactobacillus brevis surface layer protein SlpA in aqueous solution was studied using small-angle X-ray scattering and transmission electron microscopy. The proteins were found out to interact with each other forming stable globular oligomers of about 10 monomers. The maximum diameter of the oligomers varied between 75 Å and 435 Å.

  1. Impact of surface wettability on S-layer recrystallization: a real-time characterization by QCM-D.

    Science.gov (United States)

    Iturri, Jagoba; Vianna, Ana C; Moreno-Cencerrado, Alberto; Pum, Dietmar; Sleytr, Uwe B; Toca-Herrera, José Luis

    2017-01-01

    Quartz crystal microbalance with dissipation monitoring (QCM-D) has been employed to study the assembly and recrystallization kinetics of isolated SbpA bacterial surface proteins onto silicon dioxide substrates of different surface wettability. Surface modification by UV/ozone oxidation or by vapor deposition of 1 H ,1 H ,2 H ,2 H -perfluorododecyltrichlorosilane yielded hydrophilic or hydrophobic samples, respectively. Time evolution of frequency and dissipation factors, either individually or combined as the so-called Df plots, showed a much faster formation of crystalline coatings for hydrophobic samples, characterized by a phase-transition peak at around the 70% of the total mass adsorbed. This behavior has been proven to mimic, both in terms of kinetics and film assembly steps, the recrystallization taking place on an underlying secondary cell-wall polymer (SCWP) as found in bacteria. Complementary atomic force microscopy (AFM) experiments corroborate these findings and reveal the impact on the final structure achieved.

  2. Impact of surface wettability on S-layer recrystallization: a real-time characterization by QCM-D

    Directory of Open Access Journals (Sweden)

    Jagoba Iturri

    2017-01-01

    Full Text Available Quartz crystal microbalance with dissipation monitoring (QCM-D has been employed to study the assembly and recrystallization kinetics of isolated SbpA bacterial surface proteins onto silicon dioxide substrates of different surface wettability. Surface modification by UV/ozone oxidation or by vapor deposition of 1H,1H,2H,2H-perfluorododecyltrichlorosilane yielded hydrophilic or hydrophobic samples, respectively. Time evolution of frequency and dissipation factors, either individually or combined as the so-called Df plots, showed a much faster formation of crystalline coatings for hydrophobic samples, characterized by a phase-transition peak at around the 70% of the total mass adsorbed. This behavior has been proven to mimic, both in terms of kinetics and film assembly steps, the recrystallization taking place on an underlying secondary cell-wall polymer (SCWP as found in bacteria. Complementary atomic force microscopy (AFM experiments corroborate these findings and reveal the impact on the final structure achieved.

  3. Loss of PodJ in Agrobacterium tumefaciens Leads to Ectopic Polar Growth, Branching, and Reduced Cell Division.

    Science.gov (United States)

    Anderson-Furgeson, James C; Zupan, John R; Grangeon, Romain; Zambryski, Patricia C

    2016-07-01

    Agrobacterium tumefaciens is a rod-shaped Gram-negative bacterium that elongates by unipolar addition of new cell envelope material. Approaching cell division, the growth pole transitions to a nongrowing old pole, and the division site creates new growth poles in sibling cells. The A. tumefaciens homolog of the Caulobacter crescentus polar organizing protein PopZ localizes specifically to growth poles. In contrast, the A. tumefaciens homolog of the C. crescentus polar organelle development protein PodJ localizes to the old pole early in the cell cycle and accumulates at the growth pole as the cell cycle proceeds. FtsA and FtsZ also localize to the growth pole for most of the cell cycle prior to Z-ring formation. To further characterize the function of polar localizing proteins, we created a deletion of A. tumefaciens podJ (podJAt). ΔpodJAt cells display ectopic growth poles (branching), growth poles that fail to transition to an old pole, and elongated cells that fail to divide. In ΔpodJAt cells, A. tumefaciens PopZ-green fluorescent protein (PopZAt-GFP) persists at nontransitioning growth poles postdivision and also localizes to ectopic growth poles, as expected for a growth-pole-specific factor. Even though GFP-PodJAt does not localize to the midcell in the wild type, deletion of podJAt impacts localization, stability, and function of Z-rings as assayed by localization of FtsA-GFP and FtsZ-GFP. Z-ring defects are further evidenced by minicell production. Together, these data indicate that PodJAt is a critical factor for polar growth and that ΔpodJAt cells display a cell division phenotype, likely because the growth pole cannot transition to an old pole. How rod-shaped prokaryotes develop and maintain shape is complicated by the fact that at least two distinct species-specific growth modes exist: uniform sidewall insertion of cell envelope material, characterized in model organisms such as Escherichia coli, and unipolar growth, which occurs in several

  4. Loss of PopZ At activity in Agrobacterium tumefaciens by Deletion or Depletion Leads to Multiple Growth Poles, Minicells, and Growth Defects.

    Science.gov (United States)

    Grangeon, Romain; Zupan, John; Jeon, Yeonji; Zambryski, Patricia C

    2017-11-14

    Agrobacterium tumefaciens grows by addition of peptidoglycan (PG) at one pole of the bacterium. During the cell cycle, the cell needs to maintain two different developmental programs, one at the growth pole and another at the inert old pole. Proteins involved in this process are not yet well characterized. To further characterize the role of pole-organizing protein A. tumefaciens PopZ (PopZ At ), we created deletions of the five PopZ At domains and assayed their localization. In addition, we created a popZ At deletion strain (Δ popZ At ) that exhibited growth and cell division defects with ectopic growth poles and minicells, but the strain is unstable. To overcome the genetic instability, we created an inducible PopZ At strain by replacing the native ribosome binding site with a riboswitch. Cultivated in a medium without the inducer theophylline, the cells look like Δ popZ At cells, with a branching and minicell phenotype. Adding theophylline restores the wild-type (WT) cell shape. Localization experiments in the depleted strain showed that the domain enriched in proline, aspartate, and glutamate likely functions in growth pole targeting. Helical domains H3 and H4 together also mediate polar localization, but only in the presence of the WT protein, suggesting that the H3 and H4 domains multimerize with WT PopZ At , to stabilize growth pole accumulation of PopZ At IMPORTANCE Agrobacterium tumefaciens is a rod-shaped bacterium that grows by addition of PG at only one pole. The factors involved in maintaining cell asymmetry during the cell cycle with an inert old pole and a growing new pole are not well understood. Here we investigate the role of PopZ At , a homologue of Caulobacter crescentus PopZ (PopZ Cc ), a protein essential in many aspects of pole identity in C. crescentus We report that the loss of PopZ At leads to the appearance of branching cells, minicells, and overall growth defects. As many plant and animal pathogens also employ polar growth

  5. In Silico Discovery and In Vitro Validation of Catechol-Containing Sulfonohydrazide Compounds as Potent Inhibitor/span>s of the Diguanylate Cyclase PleD.

    Science.gov (United States)

    Fernicola, Silvia; Paiardini, Alessandro; Giardina, Giorgio; Rampioni, Giordano; Leoni, Livia; Cutruzzolà, Francesca; Rinaldo, Serena

    2016-01-01

    Biofilm formation is responsible for increased antibiotic tolerance in pathogenic bacteria. Cyclic di-GMP (c-di-GMP) is a widely used second-messenger signal that plays a key role in bacterial biofilm formation. c-di-GMP is synthesized by diguanylate cyclases (DGCs), a conserved class of enzymes absent in mammals and hence considered attractive molecular targets for the development of antibiofilm agents. Here, the results of a virtual screening approach aimed at identifying small-molecule inhibitors of the DGC PleD from Caulobacter crescentus are described. A three-dimensional (3D) pharmacophore model, derived from the mode of binding of GTP to the active site of PleD, was exploited to screen the ZINC database of compounds. Seven virtual hits were tested in vitro for their ability to inhibit the activity of purified PleD by using circular dichroism spectroscopy. Two drug-like molecules with a catechol moiety and a sulfonohydrazide scaffold were shown to competitively inhibit PleD at the low-micromolar range (50% inhibitory concentration [IC50] of ∼11 μM). Their predicted binding mode highlighted key structural features presumably responsible for the efficient inhibition of PleD by both hits. These molecules represent the most potent in vitro inhibitors of PleD identified so far and could therefore result in useful leads for the development of novel classes of antimicrobials able to hamper biofilm formation. Biofilm-mediated infections are difficult to eradicate, posing a threatening health issue worldwide. The capability of bacteria to form biofilms is almost universally stimulated by the second messenger c-di-GMP. This evidence has boosted research in the last decade for the development of new antibiofilm strategies interfering with c-di-GMP metabolism. Here, two potent inhibitor/span>s of c-di-GMP synthesis have been identified in silico and characterized in vitro by using the well-characterized DGC enzyme PleD from C. crescentus as a structural template and

  6. Toxin inhibition in i>C. crescentus VapBC1 is mediated by a flexible pseudo-palindromic protein motif and modulated by DNA binding

    DEFF Research Database (Denmark)

    Bendtsen, Kirstine Louise; Xu, Kehan; Luckmann, Majbritt

    2017-01-01

    architectural rearrangement of conserved TA interactions in which C-terminal extended structures of the antitoxin VapB1 swap positions to interlock the complex in the DNA-bound state. We further show that a pseudo-palindromic protein sequence in the antitoxin is responsible for this interaction and required...

  7. The Ctp type IVb pilus locus of Agrobacterium tumefaciens directs formation of the common pili and contributes to reversible surface attachment.

    Science.gov (United States)

    Wang, Yi; Haitjema, Charles H; Fuqua, Clay

    2014-08-15

    Agrobacterium tumefaciens can adhere to plant tissues and abiotic surfaces and forms biofilms. Cell surface appendages called pili play an important role in adhesion and biofilm formation in diverse bacterial systems. The A. tumefaciens C58 genome sequence revealed the presence of the ctpABCDEFGHI genes (cluster of type IV pili; Atu0216 to Atu0224), homologous to tad-type pilus systems from several bacteria, including Aggregatibacter actinomycetemcomitans and Caulobacter crescentus. These systems fall into the type IVb pilus group, which can function in bacterial adhesion. Transmission electron microscopy of A. tumefaciens revealed the presence of filaments, significantly thinner than flagella and often bundled, associated with cell surfaces and shed into the external milieu. In-frame deletion mutations of all of the ctp genes, with the exception of ctpF, resulted in nonpiliated derivatives. Mutations in ctpA (a pilin homologue), ctpB, and ctpG decreased early attachment and biofilm formation. The adherence of the ctpA mutant could be restored by ectopic expression of the paralogous pilA gene. The ΔctpA ΔpilA double pilin mutant displayed a diminished biovolume and lower biofilm height than the wild type under flowing conditions. Surprisingly, however, the ctpCD, ctpE, ctpF, ctpH, and ctpI mutants formed normal biofilms and showed enhanced reversible attachment. In-frame deletion of the ctpA pilin gene in the ctpCD, ctpE, ctpF, ctpH, and ctpI mutants caused the same attachment-deficient phenotype as the ctpA single mutant. Collectively, these findings indicate that the ctp locus is involved in pilus assembly and that nonpiliated mutants, which retain the CtpA pilin, are proficient in attachment and adherence. Copyright © 2014, American Society for Microbiology. All Rights Reserved.

  8. Absence of the Polar Organizing Protein PopZ Results in Reduced and Asymmetric Cell Division in Agrobacterium tumefaciens.

    Science.gov (United States)

    Howell, Matthew; Aliashkevich, Alena; Salisbury, Anne K; Cava, Felipe; Bowman, Grant R; Brown, Pamela J B

    2017-09-01

    Agrobacterium tumefaciens is a rod-shaped bacterium that grows by polar insertion of new peptidoglycan during cell elongation. As the cell cycle progresses, peptidoglycan synthesis at the pole ceases prior to insertion of new peptidoglycan at midcell to enable cell division. The A. tumefaciens homolog of the Caulobacter crescentus polar organelle development protein PopZ has been identified as a growth pole marker and a candidate polar growth-promoting factor. Here, we characterize the function of PopZ in cell growth and division of A. tumefaciens Consistent with previous observations, we observe that PopZ localizes specifically to the growth pole in wild-type cells. Despite the striking localization pattern of PopZ, we find the absence of the protein does not impair polar elongation or cause major changes in the peptidoglycan composition. Instead, we observe an atypical cell length distribution, including minicells, elongated cells, and cells with ectopic poles. Most minicells lack DNA, suggesting a defect in chromosome segregation. Furthermore, the canonical cell division proteins FtsZ and FtsA are misplaced, leading to asymmetric sites of cell constriction. Together, these data suggest that PopZ plays an important role in the regulation of chromosome segregation and cell division. IMPORTANCE A. tumefaciens is a bacterial plant pathogen and a natural genetic engineer. However, very little is known about the spatial and temporal regulation of cell wall biogenesis that leads to polar growth in this bacterium. Understanding the molecular basis of A. tumefaciens growth may allow for the development of innovations to prevent disease or to promote growth during biotechnology applications. Finally, since many closely related plant and animal pathogens exhibit polar growth, discoveries in A. tumefaciens may be broadly applicable for devising antimicrobial strategies. Copyright © 2017 American Society for Microbiology.

  9. ParABS system in chromosome partitioning in the bacterium Myxococcus xanthus.

    Directory of Open Access Journals (Sweden)

    Antonio A Iniesta

    Full Text Available Chromosome segregation is an essential cellular function in eukaryotic and prokaryotic cells. The ParABS system is a fundamental player for a mitosis-like process in chromosome partitioning in many bacterial species. This work shows that the social bacterium Myxococcus xanthus also uses the ParABS system for chromosome segregation. Its large prokaryotic genome of 9.1 Mb contains 22 parS sequences near the origin of replication, and it is shown here that M. xanthus ParB binds preferentially to a consensus parS sequence in vitro. ParB and ParA are essential for cell viability in M. xanthus as in Caulobacter crescentus, but unlike in many other bacteria. Absence of ParB results in anucleate cells, chromosome segregation defects and loss of viability. Analysis of ParA subcellular localization shows that it clusters at the poles in all cells, and in some, in the DNA-free cell division plane between two chromosomal DNA masses. This ParA localization pattern depends on ParB but not on FtsZ. ParB inhibits the nonspecific interaction of ParA with DNA, and ParA colocalizes with chromosomal DNA only when ParB is depleted. The subcellular localization of ParB suggests a single ParB-parS complex localized at the edge of the nucleoid, next to a polar ParA cluster, with a second ParB-parS complex migrating after the replication of parS takes place to the opposite nucleoid edge, next to the other polar ParA cluster.

  10. Model-based deconvolution of cell cycle time-series data reveals gene expression details at high resolution.

    Directory of Open Access Journals (Sweden)

    Dan Siegal-Gaskins

    2009-08-01

    Full Text Available In both prokaryotic and eukaryotic cells, gene expression is regulated across the cell cycle to ensure "just-in-time" assembly of select cellular structures and molecular machines. However, present in all time-series gene expression measurements is variability that arises from both systematic error in the cell synchrony process and variance in the timing of cell division at the level of the single cell. Thus, gene or protein expression data collected from a population of synchronized cells is an inaccurate measure of what occurs in the average single-cell across a cell cycle. Here, we present a general computational method to extract "single-cell"-like information from population-level time-series expression data. This method removes the effects of 1 variance in growth rate and 2 variance in the physiological and developmental state of the cell. Moreover, this method represents an advance in the deconvolution of molecular expression data in its flexibility, minimal assumptions, and the use of a cross-validation analysis to determine the appropriate level of regularization. Applying our deconvolution algorithm to cell cycle gene expression data from the dimorphic bacterium Caulobacter crescentus, we recovered critical features of cell cycle regulation in essential genes, including ctrA and ftsZ, that were obscured in population-based measurements. In doing so, we highlight the problem with using population data alone to decipher cellular regulatory mechanisms and demonstrate how our deconvolution algorithm can be applied to produce a more realistic picture of temporal regulation in a cell.

  11. Chemistry with an Artificial Primer of Polyhydroxybutyrate Synthase Suggests a Mechanism for Chain Termination

    Science.gov (United States)

    2015-01-01

    Polyhydroxybutyrate (PHB) synthases (PhaCs) catalyze the conversion of 3-(R)-hydroxybutyryl CoA (HBCoA) to PHB, which is deposited as granules in the cytoplasm of microorganisms. The class I PhaC from Caulobacter crescentus (PhaCCc) is a highly soluble protein with a turnover number of 75 s–1 and no lag phase in coenzyme A (CoA) release. Studies with [1-14C]HBCoA and PhaCCc monitored by sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS–PAGE) and autoradiography reveal that the rate of elongation is much faster than the rate of initiation. Priming with the artificial primer [3H]sTCoA and monitoring for CoA release reveal a single CoA/PhaC, suggesting that the protein is uniformly loaded and that the elongation process could be studied. Reaction of sT-PhaCCc with [1-14C]HBCoA revealed that priming with sTCoA increased the uniformity of elongation, allowing distinct polymerization species to be observed by SDS–PAGE and autoradiography. However, in the absence of HBCoA, [3H]sT-PhaC unexpectedly generates [3H]sDCoA with a rate constant of 0.017 s–1. We propose that the [3H]sDCoA forms via attack of CoA on the oxoester of the [3H]sT-PhaC chain, leaving the synthase attached to a single HB unit. Comparison of the relative rate constants of thiolysis by CoA and elongation by PhaCCc, and the size of the PHB polymer generated in vivo, suggests a mechanism for chain termination and reinitiation. PMID:25741756

  12. Global analysis of double-strand break processing reveals in vivo properties of the helicase-nuclease complex AddAB.

    Science.gov (United States)

    Badrinarayanan, Anjana; Le, Tung B K; Spille, Jan-Hendrik; Cisse, Ibrahim I; Laub, Michael T

    2017-05-01

    In bacteria, double-strand break (DSB) repair via homologous recombination is thought to be initiated through the bi-directional degradation and resection of DNA ends by a helicase-nuclease complex such as AddAB. The activity of AddAB has been well-studied in vitro, with translocation speeds between 400-2000 bp/s on linear DNA suggesting that a large section of DNA around a break site is processed for repair. However, the translocation rate and activity of AddAB in vivo is not known, and how AddAB is regulated to prevent excessive DNA degradation around a break site is unclear. To examine the functions and mechanistic regulation of AddAB inside bacterial cells, we developed a next-generation sequencing-based approach to assay DNA processing after a site-specific DSB was introduced on the chromosome of Caulobacter crescentus. Using this assay we determined the in vivo rates of DSB processing by AddAB and found that putative chi sites attenuate processing in a RecA-dependent manner. This RecA-mediated regulation of AddAB prevents the excessive loss of DNA around a break site, limiting the effects of DSB processing on transcription. In sum, our results, taken together with prior studies, support a mechanism for regulating AddAB that couples two key events of DSB repair-the attenuation of DNA-end processing and the initiation of homology search by RecA-thereby helping to ensure that genomic integrity is maintained during DSB repair.

  13. Quantification of ploidy in proteobacteria revealed the existence of monoploid, (mero-oligoploid and polyploid species.

    Directory of Open Access Journals (Sweden)

    Vito Pecoraro

    Full Text Available Bacteria are generally assumed to be monoploid (haploid. This assumption is mainly based on generalization of the results obtained with the most intensely studied model bacterium, Escherichia coli (a gamma-proteobacterium, which is monoploid during very slow growth. However, several species of proteobacteria are oligo- or polyploid, respectively. To get a better overview of the distribution of ploidy levels, genome copy numbers were quantified in four species of three different groups of proteobacteria. A recently developed Real Time PCR approach, which had been used to determine the ploidy levels of halophilic archaea, was optimized for the quantification of genome copy numbers of bacteria. Slow-growing (doubling time 103 minutes and fast-growing (doubling time 25 minutes E. coli cultures were used as a positive control. The copy numbers of the origin and terminus region of the chromosome were determined and the results were in excellent agreement with published data. The approach was also used to determine the ploidy levels of Caulobacter crescentus (an alpha-proteobacterium and Wolinella succinogenes (an epsilon-proteobacterium, both of which are monoploid. In contrast, Pseudomonas putida (a gamma-proteobacterium contains 20 genome copies and is thus polyploid. A survey of the proteobacteria with experimentally-determined genome copy numbers revealed that only three to four of 11 species are monoploid and thus monoploidy is not typical for proteobacteria. The ploidy level is not conserved within the groups of proteobacteria, and there are no obvious correlations between the ploidy levels with other parameters like genome size, optimal growth temperature or mode of life.

  14. The S-layer protein of Lactobacillus acidophilus ATCC 4356 : identification and characterisation of domains responsible for S-protein assembly and cell wall binding

    NARCIS (Netherlands)

    Smit, E.; Oling, F.; Demel, R.; Martinez, B.; Pouwels, P.H.

    2001-01-01

    Lactobacillus acidophilus, like many other bacteria, harbors a surface layer consisting of a protein (SA-protein) of 43 kDa. SA-protein could be readily extracted and crystallized in vitro into large crystalline patches on lipid monolayers with a net negative charge but not on lipids with a net

  15. Structural and functional analysis of the S-layer protein crystallisation domain of Lactobacillus acidophilus ATCC 4356 : evidence for protein : protein interaction of two subdomains

    NARCIS (Netherlands)

    Smit, E.; Jager, D.; Martinez, B.; Tielen, F.J.; Pouwels, P.H.

    2002-01-01

    The structure of the crystallisation domain, SAN, of the S A-protein of Lactobacillus acidophilus ATCC 4356 was analysed by insertion and deletion mutagenesis, and by proteolytic treatment. Mutant S A-protein synthesised in Escherichia coli with 7-13 amino acid insertions near the N terminus or

  16. n-Heptyl xanthate adsorption on a ZnS layer synthesized on germanium: an in situ attenuated total reflection IR study.

    Science.gov (United States)

    Fredriksson, Andreas; Larsson, Margareta L; Holmgren, Allan

    2005-06-01

    Adsorption of n-heptyl xanthate on synthesized zinc sulfide was followed in situ by monitoring the methylene absorption band at 2925 cm(-1). The zinc sulfide surface used in the adsorption experiments was synthesized on a germanium internal reflection element using the chemical bath deposition method. Characterization of the adsorbent surface was performed by X-ray photoelectron spectroscopy. The time needed to reach adsorption equilibrium varied with the initial concentration of the aqueous potassium heptyl xanthate solution. The amount of adsorbed xanthate ions increased with the concentration of the solution within the range studied (10 microM-50 mM). The experimental data are reasonably well described by the Langmuir adsorption isotherm. Polarized infrared attenuated total reflection (ATR) was used to determine the average orientation of the heptyl chains by measuring the absorbance of the infrared beam polarized perpendicularly and parallely to the plane of incidence. Measured absorbances were corrected for contribution from heptyl xanthate in bulk solution.

  17. The S-layer protein of Lactobacillus acidophilus ATCC 4356 : Identification and characterisation of domains responsible for S-protein assembly and cell wall binding

    NARCIS (Netherlands)

    Smit, E; Oling, F; Demel, R; Martinez, B; Pouwels, PH

    2001-01-01

    Lactobacillus acidophilus, like many other bacteria, harbors a surface layer consisting of a protein (S-A-protein) of 43 kDa. S-A-protein could be readily extracted and crystallized in vitro into large crystalline patches on lipid monolayers with a net negative charge but not on lipids with a net

  18. Phylogenomics and signature proteins for the alpha Proteobacteria and its main groups

    Directory of Open Access Journals (Sweden)

    Mok Amy

    2007-11-01

    Full Text Available Abstract Background Alpha proteobacteria are one of the largest and most extensively studied groups within bacteria. However, for these bacteria as a whole and for all of its major subgroups (viz. Rhizobiales, Rhodobacterales, Rhodospirillales, Rickettsiales, Sphingomonadales and Caulobacterales, very few or no distinctive molecular or biochemical characteristics are known. Results We have carried out comprehensive phylogenomic analyses by means of Blastp and PSI-Blast searches on the open reading frames in the genomes of several α-proteobacteria (viz. Bradyrhizobium japonicum, Brucella suis, Caulobacter crescentus, Gluconobacter oxydans, Mesorhizobium loti, Nitrobacter winogradskyi, Novosphingobium aromaticivorans, Rhodobacter sphaeroides 2.4.1, Silicibacter sp. TM1040, Rhodospirillum rubrum and Wolbachia (Drosophila endosymbiont. These studies have identified several proteins that are distinctive characteristics of all α-proteobacteria, as well as numerous proteins that are unique repertoires of all of its main orders (viz. Rhizobiales, Rhodobacterales, Rhodospirillales, Rickettsiales, Sphingomonadales and Caulobacterales and many families (viz. Rickettsiaceae, Anaplasmataceae, Rhodospirillaceae, Acetobacteraceae, Bradyrhiozobiaceae, Brucellaceae and Bartonellaceae. Many other proteins that are present at different phylogenetic depths in α-proteobacteria provide important information regarding their evolution. The evolutionary relationships among α-proteobacteria as deduced from these studies are in excellent agreement with their branching pattern in the phylogenetic trees and character compatibility cliques based on concatenated sequences for many conserved proteins. These studies provide evidence that the major groups within α-proteobacteria have diverged in the following order: (Rickettsiales(Rhodospirillales (Sphingomonadales (Rhodobacterales (Caulobacterales-Parvularculales (Rhizobiales. We also describe two conserved inserts in DNA

  19. Phylogenomics and signature proteins for the alpha Proteobacteria and its main groups

    Science.gov (United States)

    Gupta, Radhey S; Mok, Amy

    2007-01-01

    Background Alpha proteobacteria are one of the largest and most extensively studied groups within bacteria. However, for these bacteria as a whole and for all of its major subgroups (viz. Rhizobiales, Rhodobacterales, Rhodospirillales, Rickettsiales, Sphingomonadales and Caulobacterales), very few or no distinctive molecular or biochemical characteristics are known. Results We have carried out comprehensive phylogenomic analyses by means of Blastp and PSI-Blast searches on the open reading frames in the genomes of several α-proteobacteria (viz. Bradyrhizobium japonicum, Brucella suis, Caulobacter crescentus, Gluconobacter oxydans, Mesorhizobium loti, Nitrobacter winogradskyi, Novosphingobium aromaticivorans, Rhodobacter sphaeroides 2.4.1, Silicibacter sp. TM1040, Rhodospirillum rubrum and Wolbachia (Drosophila) endosymbiont). These studies have identified several proteins that are distinctive characteristics of all α-proteobacteria, as well as numerous proteins that are unique repertoires of all of its main orders (viz. Rhizobiales, Rhodobacterales, Rhodospirillales, Rickettsiales, Sphingomonadales and Caulobacterales) and many families (viz. Rickettsiaceae, Anaplasmataceae, Rhodospirillaceae, Acetobacteraceae, Bradyrhiozobiaceae, Brucellaceae and Bartonellaceae). Many other proteins that are present at different phylogenetic depths in α-proteobacteria provide important information regarding their evolution. The evolutionary relationships among α-proteobacteria as deduced from these studies are in excellent agreement with their branching pattern in the phylogenetic trees and character compatibility cliques based on concatenated sequences for many conserved proteins. These studies provide evidence that the major groups within α-proteobacteria have diverged in the following order: (Rickettsiales(Rhodospirillales (Sphingomonadales (Rhodobacterales (Caulobacterales-Parvularculales (Rhizobiales)))))). We also describe two conserved inserts in DNA Gyrase B and RNA

  20. The gdhB gene of Pseudomonas aeruginosa encodes an arginine-inducible NAD(+)-dependent glutamate dehydrogenase which is subject to allosteric regulation.

    Science.gov (United States)

    Lu, C D; Abdelal, A T

    2001-01-01

    The NAD(+)-dependent glutamate dehydrogenase (NAD-GDH) from Pseudomonas aeruginosa PAO1 was purified, and its amino-terminal amino acid sequence was determined. This sequence information was used in identifying and cloning the encoding gdhB gene and its flanking regions. The molecular mass predicted from the derived sequence for the encoded NAD-GDH was 182.6 kDa, in close agreement with that determined from sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the purified enzyme (180 kDa). Cross-linking studies established that the native NAD-GDH is a tetramer of equal subunits. Comparison of the derived amino acid sequence of NAD-GDH from P. aeruginosa with the GenBank database showed the highest homology with hypothetical polypeptides from Pseudomonas putida, Mycobacterium tuberculosis, Rickettsia prowazakii, Legionella pneumophila, Vibrio cholerae, Shewanella putrefaciens, Sinorhizobium meliloti, and Caulobacter crescentus. A moderate degree of homology, primarily in the central domain, was observed with the smaller tetrameric NAD-GDH (protomeric mass of 110 kDa) from Saccharomyces cerevisiae or Neurospora crassa. Comparison with the yet smaller hexameric GDH (protomeric mass of 48 to 55 kDa) of other prokaryotes yielded a low degree of homology that was limited to residues important for binding of substrates and for catalytic function. NAD-GDH was induced 27-fold by exogenous arginine and only 3-fold by exogenous glutamate. Primer extension experiments established that transcription of gdhB is initiated from an arginine-inducible promoter and that this induction is dependent on the arginine regulatory protein, ArgR, a member of the AraC/XyIS family of regulatory proteins. NAD-GDH was purified to homogeneity from a recombinant strain of P. aeruginosa and characterized. The glutamate saturation curve was sigmoid, indicating positive cooperativity in the binding of glutamate. NAD-GDH activity was subject to allosteric control by arginine and citrate, which

  1. [Transgenic bioinsecticides inimical to parasites, but imical to environment].

    Science.gov (United States)

    Kucińska, Jolanta; Lonc, Elzbieta; Rydzanicz, Katarzyna

    2003-01-01

    Culex and Anopheles, and Bti--mostly to Culex, Aedes and some Simmulidae. Gram-negative bacteria (Asticcacaulis excentricus, Caulobacter crescentus and Ancylobacter aquaticus) turned out also to be effective delta-endotoxin producers. They grow on simple media and do not contain proteases which could degrade Cry proteins. In some cases, 100% mosquito larvae mortality was observed as a result of an exposure to transgenic microorganisms containing Bti genes. However, transgenic techniques are still not very popular in the world, despite their efficacy in biological control of insects. The transgenic organism construction is expensive and time-consuming. Genetic engineering is still raising a lot of anxieties and doubts concerning inappropriate use of modified organisms. On the other hand, this technology could solve many problems associated with vectors of important diseases, which are still unapproachable to contemporary medicine.

  2. In situ characterization of aluminum-containing mineral-microorganism aqueous suspensions using scanning transmission X-ray microscopy.

    Science.gov (United States)

    Yoon, Tae Hyun; Johnson, Stephen B; Benzerara, Karim; Doyle, Colin S; Tyliszczak, Tolek; Shuh, David K; Brown, Gordon E

    2004-11-23

    In situ characterization of colloidal particles under hydrous conditions is one of the key requirements for understanding their state of aggregation and impact on the transport of pollutants in aqueous environments. Scanning transmission X-ray microscopy (STXM) is one of the few techniques that can satisfy this need by providing element- and chemical-state-specific 2-D maps at a spatial resolution better than 50 nm using soft X-rays from synchrotron radiation wiggler or undulator sources tuned to the absorption edges of different elements. X-ray absorption near-edge structure (XANES) spectra can also be collected simultaneously at a similar spatial resolution and can provide phase identification in many cases. In this study, we report STXM images and XANES spectroscopy measurements at or above the Al K-edge (E = 1559.6 eV) of various Al-containing minerals and synthetic oxides [alpha-Al2O3 (corundum), gamma-Al2O3, gamma-AlOOH (boehmite), alpha-Al(OH)3 (bayerite), KAl2(AlSi3O10)(OH)2 (muscovite), (Al,Mg)8(Si4O10)4(OH)8.nH2O (montmorillonite), and Mg6Al2(OH)16CO3.4H2O (hydrotalcite)] and demonstrate the capability of this spectromicroscopic tool to identify different Al-containing mineral colloids in multiphase mixtures in aqueous solution. We also demonstrate that STXM imaging at or above the C K-edge (E = 284.2 eV) and Al K-edge can provide unique information on the interactions between bacteria and Al-containing nanoparticles in aqueous suspensions. STXM images of a mixture of Caulobacter crescentus and montmorillonite and corundum particles just above the C and Al K-edges show that the mineral particles and bacteria are closely associated in aggregates, which is likely due to the binding of bacteria to clay and corundum particles by extracellular polysaccharides.

  3. Synthetic strategies for controlling inter- and intramolecular interactions: Applications in single-molecule fluorescence imaging, bioluminescence imaging, and palladium catalysis

    Science.gov (United States)

    Conley, Nicholas R.

    proximity of the Cy3 and Cy5 fluorophores, behaves as an optical photoswitch in the presence of a thiol reagent. This unique property was employed to achieve sub-diffraction-limited imaging of the stalks of Caulobacter crescentus cells with 30-nm resolution using STORM (stochastic optical reconstruction microscopy). Lastly, the synthesis of the first selenium analogue of firefly luciferin is described, and this analogue is shown to be a competent substrate for firefly luciferase (fLuc). Remarkably, it exhibits red-shifted bioluminescence emission relative to the native sulfur analogue. The in vivo performance of the selenium and sulfur analogues in imaging are compared by tail-vein injection into nude mice bearing subcutaneous tumor xenografts of a human breast cancer cell line that was stably transduced to express fLuc. Part II of this thesis begins by addressing design considerations in the development of palladium catalysts that effect oxidative transformations under mild conditions (i.e., 1 atm air, room temperature) using molecular oxygen as the terminal oxidant. A newly synthesized cationic palladium complex, [(2,9-dimethylphenanthroline)Pd(OAc)]2[OTf]2, is shown to catalyze aerobic alcohol oxidation under such conditions with an unprecedented initial turnover frequency, but the presence of partially reduced oxygen species results in competitive ligand oxidation with concomitant decrease in catalyst activity. To remedy this, oxidatively resistant ligands, which are essential for the development of next-generation, high-turnover-frequency palladium catalysts that utilize oxygen as a terminal oxidant, have been prepared and effectively employed. In addition, the first general palladium-catalyzed route to the carbonylation of diols is reported. In this system, carbon monoxide (1 atm) serves the carbonyl source, (2,9-dimethylphenanthroline)Pd(OAc) 2 acts as the catalyst, and N-chlorosuccinimide and iodosobenzene are the oxidants for 1,2- and 1,3-diols, respectively. This

  4. The architecture and conservation pattern of whole-cell control circuitry.

    Science.gov (United States)

    McAdams, Harley H; Shapiro, Lucy

    2011-05-27

    The control circuitry that directs and paces Caulobacter cell cycle progression involves the entire cell operating as an integrated system. This control circuitry monitors the environment and the internal state of the cell, including the cell topology, as it orchestrates orderly activation of cell cycle subsystems and Caulobacter's asymmetric cell division. The proteins of the Caulobacter cell cycle control system and its internal organization are co-conserved across many alphaproteobacteria species, but there are great differences in the regulatory apparatus' functionality and peripheral connectivity to other cellular subsystems from species to species. This pattern is similar to that observed for the "kernels" of the regulatory networks that regulate development of metazoan body plans. The Caulobacter cell cycle control system has been exquisitely optimized as a total system for robust operation in the face of internal stochastic noise and environmental uncertainty. When sufficient details accumulate, as for Caulobacter cell cycle regulation, the system design has been found to be eminently rational and indeed consistent with good design practices for human-designed asynchronous control systems. Copyright © 2011 Elsevier Ltd. All rights reserved.

  5. Bacterial signaling and motility: Sure bets

    Energy Technology Data Exchange (ETDEWEB)

    Zhulin, Igor B [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL)

    2008-01-01

    cells or swarms propagate and move outward like hunting wolf packs in search of additional macromolecules or prey. Upon starvation, cells aggregate at discrete foci to form mounds and then macroscopic fruiting bodies, each with hundreds of thousands of cells. The rod-shaped cells in the fruiting bodies eventually morph into spherical spores that are metabolically inactive and partially resistant to desiccation and temperature. When nutrients become available, spores can germinate and reenter the vegetative cell cycle. Two talks highlighted in this meeting review will tackle the mysteries of the gliding motility of M. xanthus in greater detail. In addition to M. xanthus, Caulobacter crescentus has extensively been investigated as a bacterial model of cell differentiation and development.

  6. Twenty-One Genome Sequences from Pseudomonas Species and 19 Genome Sequences from Diverse Bacteria Isolated from the Rhizosphere and Endosphere of Populus deltoides

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Steven D [ORNL; Utturkar, Sagar M [ORNL; Klingeman, Dawn Marie [ORNL; Johnson, Courtney M [ORNL; Martin, Stanton [ORNL; Land, Miriam L [ORNL; Lu, Tse-Yuan [ORNL; Schadt, Christopher Warren [ORNL; Doktycz, Mitchel John [ORNL; Pelletier, Dale A [ORNL

    2012-01-01

    To aid in the investigation of the Populus deltoides microbiome we generated draft genome sequences for twenty one Pseudomonas and twenty one other diverse bacteria isolated from Populus deltoides roots. Genome sequences for isolates similar to Acidovorax, Bradyrhizobium, Brevibacillus, Burkholderia, Caulobacter, Chryseobacterium, Flavobacterium, Herbaspirillum, Novosphingobium, Pantoea, Phyllobacterium, Polaromonas, Rhizobium, Sphingobium and Variovorax were generated.

  7. [Technical support in the testing of microoganisms for their ability to accumulate strontium and cesium from aqueous solutions]. Final reports, Task order No. 2

    Energy Technology Data Exchange (ETDEWEB)

    1987-06-15

    This report describes the binding of cesium and strontium ions from aqueous solution in a variety of microorganisms. Data is provided on the absorption by Ashbya gossyppi, Chlorella pyrenoidosa, Candida sp. Ml13, Saccharomyces cerevisiae, Scenedesmus obliqus, Streptococcus mutans, Anabaena flosaquae, Escherichia coli, Streptomyces viridochromogenes, Chlamydomonas reinhardtii, Rhizopus oryzae, Bacillus megaterium, Micrococcus luteus, Zoogloea ramigera, Coelastrum proboscideum, Pseudomonas aeruginosa, Citrobacter freundii, Paecilomyces marquandi, and Caulobacter fusiformis.

  8. A geometrical model for DNA organization in bacteria.

    Directory of Open Access Journals (Sweden)

    Mathias Buenemann

    Full Text Available Recent experimental studies have revealed that bacteria, such as C. crescentus, show a remarkable spatial ordering of their chromosome. A strong linear correlation has been found between the position of genes on the chromosomal map and their spatial position in the cellular volume. We show that this correlation can be explained by a purely geometrical model. Namely, self-avoidance of DNA, specific positioning of one or few DNA loci (such as origin or terminus together with the action of DNA compaction proteins (that organize the chromosome into topological domains are sufficient to get a linear arrangement of the chromosome along the cell axis. We develop a Monte-Carlo method that allows us to test our model numerically and to analyze the dependence of the spatial ordering on various physiologically relevant parameters. We show that the proposed geometrical ordering mechanism is robust and universal (i.e. does not depend on specific bacterial details. The geometrical mechanism should work in all bacteria that have compacted chromosomes with spatially fixed regions. We use our model to make specific and experimentally testable predictions about the spatial arrangement of the chromosome in mutants of C. crescentus and the growth-stage dependent ordering in E. coli.

  9. Preservation of Archaeal Surface Layer Structure During Mineralization

    Science.gov (United States)

    Kish, Adrienne; Miot, Jennyfer; Lombard, Carine; Guigner, Jean-Michel; Bernard, Sylvain; Zirah, Séverine; Guyot, François

    2016-05-01

    Proteinaceous surface layers (S-layers) are highly ordered, crystalline structures commonly found in prokaryotic cell envelopes that augment their structural stability and modify interactions with metals in the environment. While mineral formation associated with S-layers has previously been noted, the mechanisms were unconstrained. Using Sulfolobus acidocaldarius a hyperthermophilic archaeon native to metal-enriched environments and possessing a cell envelope composed only of a S-layer and a lipid cell membrane, we describe a passive process of iron phosphate nucleation and growth within the S-layer of cells and cell-free S-layer “ghosts” during incubation in a Fe-rich medium, independently of metabolic activity. This process followed five steps: (1) initial formation of mineral patches associated with S-layer; (2) patch expansion; (3) patch connection; (4) formation of a continuous mineral encrusted layer at the cell surface; (5) early stages of S-layer fossilization via growth of the extracellular mineralized layer and the mineralization of cytosolic face of the cell membrane. At more advanced stages of encrustation, encrusted outer membrane vesicles are formed, likely in an attempt to remove damaged S-layer proteins. The S-layer structure remains strikingly well preserved even upon the final step of encrustation, offering potential biosignatures to be looked for in the fossil record.

  10. Preservation of Archaeal Surface Layer Structure During Mineralization

    Science.gov (United States)

    Kish, Adrienne; Miot, Jennyfer; Lombard, Carine; Guigner, Jean-Michel; Bernard, Sylvain; Zirah, Séverine; Guyot, François

    2016-01-01

    Proteinaceous surface layers (S-layers) are highly ordered, crystalline structures commonly found in prokaryotic cell envelopes that augment their structural stability and modify interactions with metals in the environment. While mineral formation associated with S-layers has previously been noted, the mechanisms were unconstrained. Using Sulfolobus acidocaldarius a hyperthermophilic archaeon native to metal-enriched environments and possessing a cell envelope composed only of a S-layer and a lipid cell membrane, we describe a passive process of iron phosphate nucleation and growth within the S-layer of cells and cell-free S-layer “ghosts” during incubation in a Fe-rich medium, independently of metabolic activity. This process followed five steps: (1) initial formation of mineral patches associated with S-layer; (2) patch expansion; (3) patch connection; (4) formation of a continuous mineral encrusted layer at the cell surface; (5) early stages of S-layer fossilization via growth of the extracellular mineralized layer and the mineralization of cytosolic face of the cell membrane. At more advanced stages of encrustation, encrusted outer membrane vesicles are formed, likely in an attempt to remove damaged S-layer proteins. The S-layer structure remains strikingly well preserved even upon the final step of encrustation, offering potential biosignatures to be looked for in the fossil record. PMID:27221593

  11. Small-Angle X-Ray Scattering for Imaging of Surface Layers on Intact Bacteria in the Native Environment

    Science.gov (United States)

    Sekot, Gerhard; Schuster, David; Messner, Paul; Pum, Dietmar

    2013-01-01

    Crystalline cell surface layers (S-layers) represent a natural two-dimensional (2D) protein self-assembly system with nanometer-scale periodicity that decorate many prokaryotic cells. Here, we analyze the S-layer on intact bacterial cells of the Gram-positive organism Geobacillus stearothermophilus ATCC 12980 and the Gram-negative organism Aquaspirillum serpens MW5 by small-angle X-ray scattering (SAXS) and relate it to the structure obtained by transmission electron microscopy (TEM) after platinum/carbon shadowing. By measuring the scattering pattern of X rays obtained from a suspension of bacterial cells, integral information on structural elements such as the thickness and lattice parameters of the S-layers on intact, hydrated cells can be obtained nondestructively. In contrast, TEM of whole mounts is used to analyze the S-layer lattice type and parameters as well as the physical structure in a nonaqueous environment and local information on the structure is delivered. Application of SAXS to S-layer research on intact bacteria is a challenging task, as the scattering volume of the generally thin (3- to 30-nm) bacterial S-layers is low in comparison to the scattering volume of the bacterium itself. For enhancement of the scattering contrast of the S-layer in SAXS measurement, either silicification (treatment with tetraethyl orthosilicate) is used, or the difference between SAXS signals from an S-layer-deficient mutant and the corresponding S-layer-carrying bacterium is used for determination of the scattering signal. The good agreement of the SAXS and TEM data shows that S-layers on the bacterial cell surface are remarkably stable. PMID:23504021

  12. AcEST: DK948189 [AcEST

    Lifescience Database Archive (English)

    Full Text Available . 194 3e-48 tr|B4WDU8|B4WDU8_9CAUL Porphyromonas-type peptidyl-arginine deim... 193 1e-47 tr|A7HS82|A7HS82_P...K Agmatine deiminase OS=Caulobacter sp. (st... 184 3e-45 tr|Q4J052|Q4J052_AZOVI Porphyromonas-type peptidyl-arginine...Q1IBF2|Q1IBF2_PSEE4 Putative Porphyromonas-type peptidyl-argi... 180 9e-44 tr|Q1QYB3|Q1QYB3_CHRSD Porphyromonas-type peptidyl-arginin...HESH Agmatine deiminase OS=Shewanella sedimini... 179 2e-43 tr|Q4EUQ1|Q4EUQ1_LISMO Peptidyl-arginine... deiminase-like protein ... 179 2e-43 tr|Q4EK87|Q4EK87_LISMO Peptidyl-arginine deiminase-

  13. Surface protein composition of Aeromonas hydrophila strains virulent for fish: identification of a surface array protein

    Energy Technology Data Exchange (ETDEWEB)

    Dooley, J.S.G.; Trust, T.J.

    1988-02-01

    The surface protein composition of members of a serogroup of Aeromonas hydrophila was examined. Immunoblotting with antiserum raised against formalinized whole cells of A. hydrophila TF7 showed a 52K S-layer protein to be the major surface protein antigen, and impermeant Sulfo-NHS-Biotin cell surface labeling showed that the 52K S-layer protein was the only protein accessible to the Sulfo-NHS-Biotin label and effectively masked underlying outer membrane (OM) proteins. In its native surface conformation the 52K S-layer protein was only weakly reactive with a lactoperoxidase /sup 125/I surface iodination procedure. A UV-induced rough lipopolysaccharide (LPS) mutant of TF7 was found to produce an intact S layer, but a deep rough LPS mutant was unable to maintain an array on the cell surface and excreted the S-layer protein into the growth medium, indicating that a minimum LPS oligosaccharide size required for A. hydrophila S-layer anchoring. The native S layer was permeable to /sup 125/I in the lactoperoxidase radiolabeling procedure, and two major OM proteins of molecular weights 30,000 and 48,000 were iodinated. The 48K species was a peptidoglycan-associated, transmembrane protein which exhibited heat-modifiable SDS solubilization behavior characteristic of a porin protein. A 50K major peptidoglycan-associated OM protein which was not radiolabeled exhibited similar SDS heat modification characteristics and possibly represents a second porin protein.

  14. Surface-layer lattices as patterning element for multimeric extremozymes.

    Science.gov (United States)

    Ferner-Ortner-Bleckmann, Judith; Gelbmann, Nicola; Tesarz, Manfred; Egelseer, Eva M; Sleytr, Uwe B

    2013-11-25

    A promising new approach for the production of biocatalysts comprises the use of surface-layer (S-layer) lattices that present functional multimeric enzymes on their surface, thereby guaranteeing most accurate spatial distribution and orientation, as well as maximal effectiveness and stability of these enzymes. For proof of concept, a tetrameric and a trimeric extremozyme are chosen for the construction of S-layer/extremozyme fusion proteins. By using a flexible peptide linker, either one monomer of the tetrameric xylose isomerase XylA from the thermophilic Thermoanaerobacterium strain JW/SL-YS 489 or, in another approach, one monomer of the trimeric carbonic anhydrase from the methanogenic archaeon Methanosarcina thermophila are genetically linked to one monomer of the S-layer protein SbpA of Lysinibacillus sphaericus CCM 2177. After isolation and purification, the self-assembly properties of both S-layer fusion proteins as well as the specific activity of the fused enzymes are confirmed, thus indicating that the S-layer protein moiety does not influence the nature of the multimeric enzymes and vice versa. By recrystallization of the S-layer/extremozyme fusion proteins on solid supports, the active enzyme multimers are exposed on the surface of the square S-layer lattice with 13.1 nm spacing. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Surface protein composition of Aeromonas hydrophila strains virulent for fish: identification of a surface array protein

    International Nuclear Information System (INIS)

    Dooley, J.S.G.; Trust, T.J.

    1988-01-01

    The surface protein composition of members of a serogroup of Aeromonas hydrophila was examined. Immunoblotting with antiserum raised against formalinized whole cells of A. hydrophila TF7 showed a 52K S-layer protein to be the major surface protein antigen, and impermeant Sulfo-NHS-Biotin cell surface labeling showed that the 52K S-layer protein was the only protein accessible to the Sulfo-NHS-Biotin label and effectively masked underlying outer membrane (OM) proteins. In its native surface conformation the 52K S-layer protein was only weakly reactive with a lactoperoxidase 125 I surface iodination procedure. A UV-induced rough lipopolysaccharide (LPS) mutant of TF7 was found to produce an intact S layer, but a deep rough LPS mutant was unable to maintain an array on the cell surface and excreted the S-layer protein into the growth medium, indicating that a minimum LPS oligosaccharide size required for A. hydrophila S-layer anchoring. The native S layer was permeable to 125 I in the lactoperoxidase radiolabeling procedure, and two major OM proteins of molecular weights 30,000 and 48,000 were iodinated. The 48K species was a peptidoglycan-associated, transmembrane protein which exhibited heat-modifiable SDS solubilization behavior characteristic of a porin protein. A 50K major peptidoglycan-associated OM protein which was not radiolabeled exhibited similar SDS heat modification characteristics and possibly represents a second porin protein

  16. Search for Spin Filtering By Electron Tunneling Through Ferromagnetic EuS Barriers in Pbs

    Science.gov (United States)

    Figielski, T.; Morawski, A.; Wosinski, T.; Wrotek, S.; Makosa, A.; Lusakowska, E.; Story, T.; Sipatov, A. Yu.; Szczerbakow, A.; Grasza, K.; hide

    2002-01-01

    Perpendicular transport through single- and double-barrier heterostructures consisting of ferromagnetic EuS layers embedded into PbS matrix was investigated. Manifestations of both resonant tunneling and spin filtering through EuS barrier have been observed.

  17. Preparation and analysis of CdS-Cu/sub 2/S solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Mahdjoubi, L.; Derdouri, M.; Benmalek, M.

    1982-03-01

    Preliminary studies of CdS-Cu/sub 2/S solar cells prepared by the wet process were carried out. As the quality of the CdS layers has a marked influence on the performance of the final solar cell, our first concern was a study of the reproducibility of these layers. This was achieved through the characterization of Au-CdS Schottky diodes. Some physical and chemical properties of the CdS layers were also investigated.

  18. Surface (glyco-)proteins: primary structure and crystallization under microgravity conditions

    Science.gov (United States)

    Claus, H.; Akca, E.; Schultz, N.; Karbach, G.; Schlott, B.; Debaerdemaeker, T.; De Clercq, J.-P.; König, H.

    2001-08-01

    The Archaea comprise microorganisms that live under environmental extremes, like high temperature, low pH value or high salt concentration. Their cells are often covered by a single layer of (glyco)protein subunits (S-layer) in hexagonal arrangement. In order to get further hints about the molecular mechanisms of protein stabilization we compared the primary and secondary structures of archaeal S-layer (glyco)proteins. We found an increase of charged amino acids in the S-layer proteins of the extreme thermophilic species compared to their mesophilic counterparts. Our data and those of other authors suggest that ionic interactions, e.g., salt bridges seem to be played a major role in protein stabilization at high temperatures. Despite the differences in the growth optima and the predominance of some amino acids the primary structures of S-layers revealed also a significant degree of identity between phylogenetically related archaea. These obervations indicate that protein sequences of S-layers have been conserved during the evolution from extremely thermophilic to mesophilic life. To support these findings the three-dimensional structure of the S-layer proteins has to be elucidated. Recently, we described the first successful crystallization of an extreme thermophilic surface(glyco)protein under microgravity conditions.

  19. Investigating the Effect of Growth Phase on the Surface-Layer Associated Proteome of Lactobacillus acidophilus Using Quantitative Proteomics

    Directory of Open Access Journals (Sweden)

    Courtney Klotz

    2017-11-01

    Full Text Available Bacterial surface-layers (S-layers are semi-porous crystalline arrays that self-assemble to form the outermost layer of some cell envelopes. S-layers have been shown to act as scaffolding structures for the display of auxiliary proteins externally. These S-layer associated proteins have recently gained attention in probiotics due to their direct physical contact with the intestinal mucosa and potential role in cell proliferation, adhesion, and immunomodulation. A number of studies have attempted to catalog the S-layer associated proteome of Lactobacillus acidophilus NCFM under a single condition. However, due to the versatility of the cell surface, we chose to employ a multiplexing-based approach with the intention of accurately contrasting multiple conditions. In this study, a previously described lithium chloride isolation protocol was used to release proteins bound to the L. acidophilus S-layer during logarithmic and early stationary growth phases. Protein quantification values were obtained via TMT (tandem mass tag labeling combined with a triple-stage mass spectrometry (MS3 method. Results showed significant growth stage-dependent alterations to the surface-associated proteome while simultaneously highlighting the sensitivity and reproducibility of the technology. Thus, this study establishes a framework for quantifying condition-dependent changes to cell surface proteins that can easily be applied to other S-layer forming bacteria.

  20. Surface proteins from Lactobacillus kefir antagonize in vitro cytotoxic effect of Clostridium difficile toxins.

    Science.gov (United States)

    Carasi, Paula; Trejo, Fernando M; Pérez, Pablo F; De Antoni, Graciela L; Serradell, María de los Angeles

    2012-02-01

    In this work, the ability of S-layer proteins from kefir-isolated Lactobacillus kefir strains to antagonize the cytophatic effects of toxins from Clostridium difficile (TcdA and TcdB) on eukaryotic cells in vitro was tested by cell detachment assay. S-layer proteins from eight different L. kefir strains were able to inhibit the damage induced by C. difficile spent culture supernatant to Vero cells. Besides, same protective effect was observed by F-actin network staining. S-layer proteins from aggregating L. kefir strains (CIDCA 83115, 8321, 8345 and 8348) showed a higher inhibitory ability than those belonging to non-aggregating ones (CIDCA 83111, 83113, JCM 5818 and ATCC 8007), suggesting that differences in the structure could be related to the ability to antagonize the effect of clostridial toxins. Similar results were obtained using purified TcdA and TcdB. Protective effect was not affected by proteases inhibitors or heat treatment, thus indicating that proteolytic activity is not involved. Only preincubation with specific anti-S-layer antibodies significantly reduced the inhibitory effect of S-layer proteins, suggesting that this could be attributed to a direct interaction between clostridial toxins and L. kefir S-layer protein. Interestingly, the interaction of toxins with S-layer carrying bacteria was observed by dot blot and fluorescence microscopy with specific anti-TcdA or anti-TcdB antibodies, although L. kefir cells did not show protective effects. We hypothesize that the interaction between clostridial toxins and soluble S-layer molecules is different from the interaction with S-layer on the surface of the bacteria thus leading a different ability to antagonize cytotoxic effect. This is the first report showing the ability of S-layer proteins from kefir lactobacilli to antagonize biological effects of bacterial toxins. These results encourage further research on the role of bacterial surface molecules to the probiotic properties of L. kefir and could

  1. Exceptional preservation of Mn-oxidizing microbes in cave stromatolites (El Soplao, Spain)

    Science.gov (United States)

    Lozano, Rafael P.; Rossi, Carlos

    2012-05-01

    Many ferromanganese stromatolites of El Soplao Cave (N Spain) are characterized for the exceptional preservation and high diversity of microbial fossils, probably representing the best example of microbial preservation described in ferromanganese deposits so far. The El Soplao stromatolites are mainly formed by polymetallic Mn-rich oxides with subordinate and variable amounts of detrital material, and consist of both dendritic and laminar microfacies. In both microfacies, microbial forms are abundant in the relatively pure Mn-oxide rich material, whereas they are scarce in areas with significant detrital material. Microbial forms are observed either in cross section, completely embedded in the Mn-oxide-rich matrix, or in three dimensions lining the walls of pores. Based on their morphology, we have separated the most abundant microbial forms into six main morphotypes and six additional submorphotypes, most of which can be assigned to bacteria. Most morphotypes consist of coccoid, coccobacilus, or filamentous forms. Therefore they are not diagnostic of any particular bacterial group. However, the ovoid cells of morphotype B show cylindrical polar protuberances typical of prosthecate alpha-Proteobacteria. On the basis of characteristic morphological features, three submorphotypes of morphotype B can be assigned to three alpha-Proteobacteria genera: Hyphomicrobium, Pedomicrobium, and Caulobacter. This ascription is supported by the well known Mn-oxidizing behavior of both Pedomicrobium and Caulobacter, and by the common presence of Hyphomicrobium in ferromanganese deposits elsewhere. The excellent microbial preservation is partly related to the origin of the ferromanganese oxides, i.e. extracellular precipitation induced by microbial metabolism. Other factors contributing to the good microbial preservation are the relatively low degree of diagenetic alteration, and the relatively high accretion rates of stromatolites compared to other ferromanganese deposits. The

  2. Au-Interaction of Slp1 Polymers and Monolayer from Lysinibacillus sphaericus JG-B53 - QCM-D, ICP-MS and AFM as Tools for Biomolecule-metal Studies.

    Science.gov (United States)

    Suhr, Matthias; Raff, Johannes; Pollmann, Katrin

    2016-01-19

    In this publication the gold sorption behavior of surface layer (S-layer) proteins (Slp1) of Lysinibacillus sphaericus JG-B53 is described. These biomolecules arrange in paracrystalline two-dimensional arrays on surfaces, bind metals, and are thus interesting for several biotechnical applications, such as biosorptive materials for the removal or recovery of different elements from the environment and industrial processes. The deposition of Au(0) nanoparticles on S-layers, either by S-layer directed synthesis or adsorption of nanoparticles, opens new possibilities for diverse sensory applications. Although numerous studies have described the biosorptive properties of S-layers, a deeper understanding of protein-protein and protein-metal interaction still remains challenging. In the following study, inductively coupled mass spectrometry (ICP-MS) was used for the detection of metal sorption by suspended S-layers. This was correlated to measurements of quartz crystal microbalance with dissipation monitoring (QCM-D), which allows the online detection of proteinaceous monolayer formation and metal deposition, and thus, a more detailed understanding on metal binding. The ICP-MS results indicated that the binding of Au(III) to the suspended S-layer polymers is pH dependent. The maximum binding of Au(III) was obtained at pH 4.0. The QCM-D investigations enabled the detection of Au(III) sorption as well as the deposition of Au(0)-NPs in real-time during the in situ experiments. Further, this method allowed studying the influence of metal binding on the protein lattice stability of Slp1. Structural properties and protein layer stability could be visualized directly after QCM-D experiment using atomic force microscopy (AFM). In conclusion, the combination of these different methods provides a deeper understanding of metal binding by bacterial S-layer proteins in suspension or as monolayers on either bacterial cells or recrystallized surfaces.

  3. Wafer-scale production of vertical SnS multilayers for high-performing photoelectric devices.

    Science.gov (United States)

    Patel, Malkeshkumar; Kim, Hong-Sik; Kim, Joondong

    2017-10-26

    This study achieved wafer-scale, high quality tin monosulfide (SnS) layers. By using a solid-state reaction, the vertically aligned SnS layers spontaneously grew with sulphur reduction from the sputtered SnS 2 particles without any post processes. The quality of the SnS vertical layers was observed by high resolution transmission electron microscopy, which confirmed an interlayer space of 0.56 nm for a perfect match to the theoretical value. The phase purity of SnS was confirmed by Raman spectroscopy. The intrinsic energy band gap value (1.6 eV) of SnS is attractive for photoelectric devices. To form a heterojunction, the vertical SnS layers were grown on a n-type Si substrate. Due to the nanoscale size and vertical standing features of the SnS layers, a significantly low reflection (cell, the device provides a higher open circuit voltage (>300 mV). For photodetection, the response speed is faster than 15 μs for near infrared wavelength photons, which is a 1000 times improvement over the horizontally shaped device. The vertically standing SnS layers show high photoreactive performance, which confirms that the functional design of 2D materials is an effective route to achieve enhanced photoelectric devices, such as photodetectors and solar cells.

  4. Cwp84, a Clostridium difficile cysteine protease, exhibits conformational flexibility in the absence of its propeptide

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, William J. [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Roberts, April K.; Shone, Clifford C. [Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Acharya, K. Ravi, E-mail: bsskra@bath.ac.uk [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)

    2015-02-19

    Two structures of Cwp84, a cysteine protease from the S-layer of C. difficile, are presented after propeptide cleavage. They reveal the movement of three loops, two in the active-site groove and one on the surface of the lectin-like domain, exposing a hydrophobic pocket. In recent decades, the global healthcare problems caused by Clostridium difficile have increased at an alarming rate. A greater understanding of this antibiotic-resistant bacterium, particularly with respect to how it interacts with the host, is required for the development of novel strategies for fighting C. difficile infections. The surface layer (S-layer) of C. difficile is likely to be of significant importance to host–pathogen interactions. The mature S-layer is formed by a proteinaceous array consisting of multiple copies of a high-molecular-weight and a low-molecular-weight S-layer protein. These components result from the cleavage of SlpA by Cwp84, a cysteine protease. The structure of a truncated Cwp84 active-site mutant has recently been reported and the key features have been identified, providing the first structural insights into the role of Cwp84 in the formation of the S-layer. Here, two structures of Cwp84 after propeptide cleavage are presented and the three conformational changes that are observed are discussed. These changes result in a reconfiguration of the active site and exposure of the hydrophobic pocket.

  5. Indigenous bacteria may interfere with the biocontrol of plant diseases

    Science.gov (United States)

    Someya, Nobutaka; Akutsu, Katsumi

    2009-06-01

    Prodigiosin is a reddish antibiotic pigment that plays an important role in the biocontrol of plant diseases by the bacterium Serratia marcescens. However, its activity is unstable under agricultural conditions; further, it can be degraded by various environmental factors. To examine the effect of epiphytic microbes on the stability of prodigiosin used for biological control processes, we collected a total of 1,280 bacterial isolates from the phylloplane of cyclamen and tomato plants. Approximately 72% of the bacterial strains isolated from the cyclamen plants and 66% of those isolated from the tomato plants grew on minimal agar medium containing 100 μg ml-1 prodigiosin. Certain isolates obtained from both plant species exhibited prodigiosin-degrading activity. We compared the 16S rRNA gene sequences derived from the isolates with sequences in a database. The comparison revealed that the sequences determined for the prodigiosin-degrading isolates were homologous to those of the genera Pseudomonas, Caulobacter, Rhizobium, Sphingomonas, Janthinobacterium, Novosphingobium, and Rathayibacter. These results indicate that indigenous epiphytic microorganisms may interfere with the interaction between plant pathogens and biocontrol agents by degrading the antibiotics produced by the agents.

  6. Pyrosequencing-Based Assessment of the Microbial Community Structure of Pastoruri Glacier Area (Huascarán National Park, Perú), a Natural Extreme Acidic Environment.

    Science.gov (United States)

    González-Toril, Elena; Santofimia, Esther; Blanco, Yolanda; López-Pamo, Enrique; Gómez, Manuel J; Bobadilla, Miguel; Cruz, Rolando; Palomino, Edwin Julio; Aguilera, Ángeles

    2015-11-01

    The exposure of fresh sulfide-rich lithologies by the retracement of the Nevado Pastoruri glacier (Central Andes, Perú) is increasing the presence of heavy metals in the water as well as decreasing the pH, producing an acid rock drainage (ARD) process in the area. We describe the microbial communities of an extreme ARD site in Huascarán National Park as well as their correlation with the water physicochemistry. Microbial biodiversity was analyzed by FLX 454 sequencing of the 16S rRNA gene. The suggested geomicrobiological model of the area distinguishes three different zones. The proglacial zone is located in the upper part of the valley, where the ARD process is not evident yet. Most of the OTUs detected in this area were related to sequences associated with cold environments (i.e., psychrotolerant species of Cyanobacteria or Bacteroidetes). After the proglacial area, an ARD-influenced zone appeared, characterized by the presence of phylotypes related to acidophiles (Acidiphilium) as well as other species related to acidic and cold environments (i.e., acidophilic species of Chloroflexi, Clostridium and Verrumicrobia). Sulfur- and iron-oxidizing acidophilic bacteria (Acidithiobacillus) were also identified. The post-ARD area was characterized by the presence of OTUs related to microorganisms detected in soils, permafrost, high mountain environments, and deglaciation areas (Sphingomonadales, Caulobacter or Comamonadaceae).

  7. Efficacy of various chemical disinfectants on biofilms formed in spacecraft potable water system components.

    Science.gov (United States)

    Wong, Wing C; Dudinsky, Lynn A; Garcia, Veronica M; Ott, Charlie M; Castro, Victoria A

    2010-07-01

    As the provision of potable water is critical for successful habitation of the International Space Station (ISS), life support systems were installed in December 2008 to recycle both humidity from the atmosphere and urine to conserve available water in the Station. In-flight pre-consumption testing from the dispensing needle at the Potable Water Dispenser (PWD) indicated that bacterial concentrations exceeded the current ISS specifications of 50 colony-forming units (CFU) ml(-1). Subsequent investigations revealed that a corrugated stainless steel flex hose upstream of the dispensing needle in the PWD was filled with nonsterile water and left at room temperature for more than 1 month before launch. To simulate biofilm formation that was suspected in the flight system, sterile flex hoses were seeded with a consortium of bacterial isolates previously recovered from other ISS water systems, including Ralstonia pickettii, Burkholderia multivorans, Caulobacter vibrioides, and Cupriavidus pauculus. After incubation for 5 days, the hoses were challenged with various chemical disinfectants including hydrogen peroxide (H2O2), colloidal silver, and buffered pH solutions to determine the ability of the disinfectants to decrease and maintain bacterial concentrations below ISS specifications. The disinfection efficacy over time was measured by collecting daily heterotrophic plate counts after exposure to the disinfectants. A single flush with either 6% H2O2 solution or a mixture of 3% H2O2 and 400 ppb colloidal silver effectively reduced the bacterial concentrations to <1 CFU ml(-1) for a period of up to 3 months.

  8. Bacterial endophytic communities in the grapevine depend on pest management.

    Directory of Open Access Journals (Sweden)

    Andrea Campisano

    Full Text Available Microbial plant endophytes are receiving ever-increasing attention as a result of compelling evidence regarding functional interaction with the host plant. Microbial communities in plants were recently reported to be influenced by numerous environmental and anthropogenic factors, including soil and pest management. In this study we used automated ribosomal intergenic spacer analysis (ARISA fingerprinting and pyrosequencing of 16S rDNA to assess the effect of organic production and integrated pest management (IPM on bacterial endophytic communities in two widespread grapevines cultivars (Merlot and Chardonnay. High levels of the dominant Ralstonia, Burkholderia and Pseudomonas genera were detected in all the samples We found differences in the composition of endophytic communities in grapevines cultivated using organic production and IPM. Operational taxonomic units (OTUs assigned to the Mesorhizobium, Caulobacter and Staphylococcus genera were relatively more abundant in plants from organic vineyards, while Ralstonia, Burkholderia and Stenotrophomonas were more abundant in grapevines from IPM vineyards. Minor differences in bacterial endophytic communities were also found in the grapevines of the two cultivars.

  9. Bacterial endophytic communities in the grapevine depend on pest management.

    Science.gov (United States)

    Campisano, Andrea; Antonielli, Livio; Pancher, Michael; Yousaf, Sohail; Pindo, Massimo; Pertot, Ilaria

    2014-01-01

    Microbial plant endophytes are receiving ever-increasing attention as a result of compelling evidence regarding functional interaction with the host plant. Microbial communities in plants were recently reported to be influenced by numerous environmental and anthropogenic factors, including soil and pest management. In this study we used automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and pyrosequencing of 16S rDNA to assess the effect of organic production and integrated pest management (IPM) on bacterial endophytic communities in two widespread grapevines cultivars (Merlot and Chardonnay). High levels of the dominant Ralstonia, Burkholderia and Pseudomonas genera were detected in all the samples We found differences in the composition of endophytic communities in grapevines cultivated using organic production and IPM. Operational taxonomic units (OTUs) assigned to the Mesorhizobium, Caulobacter and Staphylococcus genera were relatively more abundant in plants from organic vineyards, while Ralstonia, Burkholderia and Stenotrophomonas were more abundant in grapevines from IPM vineyards. Minor differences in bacterial endophytic communities were also found in the grapevines of the two cultivars.

  10. Microbial nitrogen cycling in Arctic snowpacks

    International Nuclear Information System (INIS)

    Larose, Catherine; Vogel, Timothy M; Dommergue, Aurélien

    2013-01-01

    Arctic snowpacks are often considered as chemical reactors for a variety of chemicals deposited through wet and dry events, but are overlooked as potential sites for microbial metabolism of reactive nitrogen species. The fate of deposited species is critical since warming leads to the transfer of contaminants to snowmelt-fed ecosystems. Here, we examined the role of microorganisms and the potential pathways involved in nitrogen cycling in the snow. Next generation sequencing data were used to follow functional gene abundances and a 16S rRNA (ribosomal ribonucleic acid) gene microarray was used to follow shifts in microbial community structure during a two-month spring-time field study at a high Arctic site, Svalbard, Norway (79° N). We showed that despite the low temperatures and limited water supply, microbial communities inhabiting the snow cover demonstrated dynamic shifts in their functional potential to follow several different pathways of the nitrogen cycle. In addition, microbial specific phylogenetic probes tracked different nitrogen species over time. For example, probes for Roseomonas tracked nitrate concentrations closely and probes for Caulobacter tracked ammonium concentrations after a delay of one week. Nitrogen cycling was also shown to be a dominant process at the base of the snowpack. (letter)

  11. Bacterial Endophytic Communities in the Grapevine Depend on Pest Management

    Science.gov (United States)

    Campisano, Andrea; Antonielli, Livio; Pancher, Michael; Yousaf, Sohail; Pindo, Massimo; Pertot, Ilaria

    2014-01-01

    Microbial plant endophytes are receiving ever-increasing attention as a result of compelling evidence regarding functional interaction with the host plant. Microbial communities in plants were recently reported to be influenced by numerous environmental and anthropogenic factors, including soil and pest management. In this study we used automated ribosomal intergenic spacer analysis (ARISA) fingerprinting and pyrosequencing of 16S rDNA to assess the effect of organic production and integrated pest management (IPM) on bacterial endophytic communities in two widespread grapevines cultivars (Merlot and Chardonnay). High levels of the dominant Ralstonia, Burkholderia and Pseudomonas genera were detected in all the samples We found differences in the composition of endophytic communities in grapevines cultivated using organic production and IPM. Operational taxonomic units (OTUs) assigned to the Mesorhizobium, Caulobacter and Staphylococcus genera were relatively more abundant in plants from organic vineyards, while Ralstonia, Burkholderia and Stenotrophomonas were more abundant in grapevines from IPM vineyards. Minor differences in bacterial endophytic communities were also found in the grapevines of the two cultivars. PMID:25387008

  12. Crude oil treatment leads to shift of bacterial communities in soils from the deep active layer and upper permafrost along the China-Russia Crude Oil Pipeline route.

    Science.gov (United States)

    Yang, Sizhong; Wen, Xi; Zhao, Liang; Shi, Yulan; Jin, Huijun

    2014-01-01

    The buried China-Russia Crude Oil Pipeline (CRCOP) across the permafrost-associated cold ecosystem in northeastern China carries a risk of contamination to the deep active layers and upper permafrost in case of accidental rupture of the embedded pipeline or migration of oil spills. As many soil microbes are capable of degrading petroleum, knowledge about the intrinsic degraders and the microbial dynamics in the deep subsurface could extend our understanding of the application of in-situ bioremediation. In this study, an experiment was conducted to investigate the bacterial communities in response to simulated contamination to deep soil samples by using 454 pyrosequencing amplicons. The result showed that bacterial diversity was reduced after 8-weeks contamination. A shift in bacterial community composition was apparent in crude oil-amended soils with Proteobacteria (esp. α-subdivision) being the dominant phylum, together with Actinobacteria and Firmicutes. The contamination led to enrichment of indigenous bacterial taxa like Novosphingobium, Sphingobium, Caulobacter, Phenylobacterium, Alicylobacillus and Arthrobacter, which are generally capable of degrading polycyclic aromatic hydrocarbons (PAHs). The community shift highlighted the resilience of PAH degraders and their potential for in-situ degradation of crude oil under favorable conditions in the deep soils.

  13. Mucosal Immunogenicity of Genetically Modified Lactobacillus acidophilus Expressing an HIV-1 Epitope within the Surface Layer Protein.

    Directory of Open Access Journals (Sweden)

    Akinobu Kajikawa

    Full Text Available Surface layer proteins of probiotic lactobacilli are theoretically efficient epitope-displaying scaffolds for oral vaccine delivery due to their high expression levels and surface localization. In this study, we constructed genetically modified Lactobacillus acidophilus strains expressing the membrane proximal external region (MPER from human immunodeficiency virus type 1 (HIV-1 within the context of the major S-layer protein, SlpA. Intragastric immunization of mice with the recombinants induced MPER-specific and S-layer protein-specific antibodies in serum and mucosal secretions. Moreover, analysis of systemic SlpA-specific cytokines revealed that the responses appeared to be Th1 and Th17 dominant. These findings demonstrated the potential use of the Lactobacillus S-layer protein for development of oral vaccines targeting specific peptides.

  14. Mucosal Immunogenicity of Genetically Modified Lactobacillus acidophilus Expressing an HIV-1 Epitope within the Surface Layer Protein

    Science.gov (United States)

    Kajikawa, Akinobu; Zhang, Lin; LaVoy, Alora; Bumgardner, Sara; Klaenhammer, Todd R.; Dean, Gregg A.

    2015-01-01

    Surface layer proteins of probiotic lactobacilli are theoretically efficient epitope-displaying scaffolds for oral vaccine delivery due to their high expression levels and surface localization. In this study, we constructed genetically modified Lactobacillus acidophilus strains expressing the membrane proximal external region (MPER) from human immunodeficiency virus type 1 (HIV-1) within the context of the major S-layer protein, SlpA. Intragastric immunization of mice with the recombinants induced MPER-specific and S-layer protein-specific antibodies in serum and mucosal secretions. Moreover, analysis of systemic SlpA-specific cytokines revealed that the responses appeared to be Th1 and Th17 dominant. These findings demonstrated the potential use of the Lactobacillus S-layer protein for development of oral vaccines targeting specific peptides. PMID:26509697

  15. Three-dimensional structure of the surface layer protein of Aquaspirilium serpens VHA determined by electron crystallography

    Energy Technology Data Exchange (ETDEWEB)

    Dickson, M.R.; Downing, K.H.; Wu, W.H.; Glaeser, R.M.

    1986-09-01

    The three-dimensional structure of the protein which forms the S layer of Aquaspirilium serpens strain VHA has been determined by electron microscopy. Structures have been reconstructed to a resolution of about 1.6 nm for single-layered specimens and about 4 nm for two-layered specimens. The structure, which has hexagonal symmetry, consists of a core in the shape of a cup, with six projections arising from the rim of the cup to join adjacent subunits at the threefold symmetry axes. The model is consistent with edge views of the S layer which have been obtained in this and other work. It is now clear from this work and from three-dimensional reconstructions of other bacterial S layers that a wide diversity exists in the morphology of surface layers.

  16. Three-dimensional structure of the surface layer protein of Aquaspirillum serpens VHA determined by electron crystallography.

    Science.gov (United States)

    Dickson, M R; Downing, K H; Wu, W H; Glaeser, R M

    1986-09-01

    The three-dimensional structure of the protein which forms the S layer of Aquaspirillum serpens strain VHA has been determined by electron microscopy. Structures have been reconstructed to a resolution of about 1.6 nm for single-layered specimens and about 4 nm for two-layered specimens. The structure, which has hexagonal symmetry, consists of a core in the shape of a cup, with six projections arising from the rim of the cup to join adjacent subunits at the threefold symmetry axes. The model is consistent with edge views of the S layer which have been obtained in this and other work. It is now clear from this work and from three-dimensional reconstructions of other bacterial S layers that a wide diversity exists in the morphology of surface layers.

  17. The structure and assembly of surface layer proteins : a combined approach of in silico and experimental methods

    International Nuclear Information System (INIS)

    Horejs, C.

    2011-01-01

    Self-assembly of matter is one of nature's most sophisticated strategies to organize molecules on a large scale and to create order from disorder. Surface (S-)layer proteins self-assemble in a highly reproducible and robust fashion in order to form crystalline layers that completely cover and protect prokaryotic cells. Long conserved during evolution, S-layers constitute a unique model system to study the molecular mechanisms of functional self-assembly, while additionally, they provide a basic matrix for the specific construction of ordered nanostructures. Due to their intrinsic capabilities to self-assemble into two-dimensional crystals, the elucidation of the three-dimensional structure of single S-layer proteins demands an approach beyond conventional structure determination methods. In this work, computer simulations were combined with experimental techniques in order to study the structure and intra- and intermolecular potentials guiding the proteins to self-assemble into lattices with different symmetries. Molecular dynamics, Monte Carlo methods, small-angle X-ray scattering involving a new theoretical description, and AFM-based single-molecule force spectroscopy yield new insights into the three-dimensional structure of S-layer proteins, the location, type and distribution of amino acids in S-layer lattices, the molecular mechanisms behind the self-assembly process, the mechanical stability and adaptive structural conformations that S-layer proteins are able to establish. In silico studies - embedded in an adequate experimental and theoretical scaffold - offer the possibility to calculate structural and thermodynamic features of proteins, while this work demonstrates the growing impact of such theoretical techniques in the fascinating field of biophysics at the nano-scale. (author) [de

  18. Investigation of electronic quality of electrodeposited cadmium sulphide layers from thiourea precursor for use in large area electronics

    Energy Technology Data Exchange (ETDEWEB)

    Ojo, A.A., E-mail: chartell2006@yahoo.com; Dharmadasa, I.M.

    2016-09-01

    CdS layers used in thin film solar cells and other electronic devices are usually grown by wet chemical methods using CdCl{sub 2} as the Cadmium source and either Na{sub 2}S{sub 2}O{sub 3}, NH{sub 4}S{sub 2}O{sub 3} or NH{sub 2}CSNH{sub 2} as Sulphur sources. Obviously, one of the sulphur precursors should produce more suitable CdS layers required to give the highest performing devices. This can only be achieved by comprehensive experimental work on growth and characterisation of CdS layers from the above mentioned sulphur sources. This paper presents the results observed on CdS layers grown by electrodepositing using two electrode configuration and thiourea as the sulphur precursor. X-ray diffraction (XRD), Raman spectroscopy, optical absorption, scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and photoelectrochemical (PEC) cell methods have been used to characterise the material properties. In order to test and study the electronic device quality of the layers, ohmic and rectifying contacts were fabricated on the electroplated layers. Schottky barriers, formed on the layers were also compared with previously reported work on Chemical Bath Deposited CBD-CdS layers and bulk single crystals of CdS. Comparatively, Schottky diodes fabricated on electroplated CdS layers using two-electrode system and thiourea precursor exhibit excellent electronic properties suitable for electronic devices such as thin film solar panels and large area display devices. - Highlights: • Precipitate-free electrodeposition of CdS is achievable using Thiourea precursor. • Electrodeposition of CdS using 2-electrode configuration. • The electrodeposited CdS shows excellent electronic properties. • Exploration of the effect of heat treatment temperature and heat treatment duration.

  19. Preparation and analysis of CdS-Cu/sub 2/S solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Mahdjoubi, L.; Derdouri, M.; Benmalek, M.

    1982-03-01

    Preliminary studies of CdS-Cu/sub 2/S solar cells prepared by the wet process were carried out. As the quality of the CdS layers has a marked influence on the performance of the final solar cell, the first concern of this study was the reproducibility of these layers. This was achieved through the characterization of Au-CdS Schottky diodes. Some physical and chemical properties of the CdS layers were also investigated. The first results obtained on these cells are discussed. 9 refs.

  20. Preparation and analysis of CdS-Cu/sub 2/S solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Mahdjoubi, L.; Derdouri, M.; Benmalek, M.

    1982-03-01

    Preliminary studies of CdS-Cu/sub 2/S solar cells prepared by the wet process were carried out. As the quality of the CdS layers has a marked influence on the performance of the final solar cell, our first concern was a study of the reproducibility of these layers. This was achieved through the characterization of Au-CdS Schottky diodes. Some physical and chemical properties of the CdS layers were also investigated. The first results obtained on these cells are encouraging but more work needs to be done.

  1. AUTHOR INDEX

    Indian Academy of Sciences (India)

    see Kaplan A. 343. Badr A M. Crystal growth, electrical and photophys- ical properties of Tl2S layered single crys- tals. 871. Bali Raj. Bianchi Type V magnetized string dust cosmological models with Petrov-type de- generate. 787. Banerjee Souri see Amruth B R. 637. Bannur Vishnu M. Formulation of statistical mechanics ...

  2. Role of lactobacillus cell surface hydrophobicity as probed by AFM in adhesion to surfaces at low and high ionic strength

    NARCIS (Netherlands)

    Vadillo Rodriguez, Virginia; Busscher, Hendrik; van der Mei, Henderina; Norde, Willem; de Vries, Jacob

    2005-01-01

    The S-layer present at the outermost cell surface of some lactobacillus species is known to convey hydrophobicity to the lactobacillus cell surface. Yet, it is commonly found that adhesion of lactobacilli to solid substrata does not proceed according to expectations based on cell surface

  3. Role of lactobacillus cell surface hydrophobicity as probed by AMF in adhesion to surfaces at low and high ionic strength

    NARCIS (Netherlands)

    Vadillo-Rodriguez, V.; Busscher, H.J.; Meij, van der H.C.; Vries, de J.; Norde, W.

    2005-01-01

    The S-layer present at the outermost cell surface of some lactobacillus species is known to convey hydrophobicity to the lactobacillus cell surface. Yet, it is commonly found that adhesion of lactobacilli to solid substrata does not proceed according to expectations based on cell surface

  4. Identification of genes involved in the biosynthesis and attachment of Methanococcus voltae N-linked glycans: insight into N-linked glycosylation pathways in Archaea.

    Science.gov (United States)

    Chaban, Bonnie; Voisin, Sebastien; Kelly, John; Logan, Susan M; Jarrell, Ken F

    2006-07-01

    N-linked glycosylation is recognized as an important post-translational modification across all three domains of life. However, the understanding of the genetic pathways for the assembly and attachment of N-linked glycans in eukaryotic and bacterial systems far outweighs the knowledge of comparable processes in Archaea. The recent characterization of a novel trisaccharide [beta-ManpNAcA6Thr-(1-4)-beta-GlcpNAc3NAcA-(1-3)-beta-GlcpNAc]N-linked to asparagine residues in Methanococcus voltae flagellin and S-layer proteins affords new opportunities to investigate N-linked glycosylation pathways in Archaea. In this contribution, the insertional inactivation of several candidate genes within the M. voltae genome and their resulting effects on flagellin and S-layer glycosylation are reported. Two of the candidate genes were shown to have effects on flagellin and S-layer protein molecular mass and N-linked glycan structure. Further examination revealed inactivation of either of these two genes also had effects on flagella assembly. These genes, designated agl (archaeal glycosylation) genes, include a glycosyl transferase (aglA) involved in the attachment of the terminal sugar to the glycan and an STT3 oligosaccharyl transferase homologue (aglB) involved in the transfer of the complete glycan to the flagellin and S-layer proteins. These findings document the first experimental evidence for genes involved in any glycosylation process within the domain Archaea.

  5. Crystal growth, electrical and photophysical properties of Tl2S ...

    Indian Academy of Sciences (India)

    The electrical conductivity measurements were extended to elucidate the temper- ature dependence of the Hall coefficient for Tl2S layered single crystals and to determine important physical parameters. Also the scattering mechanism for the charge carriers was elucidated and discussed in this section. In this experiment.

  6. Research Article Special Issue

    African Journals Online (AJOL)

    2016-05-15

    May 15, 2016 ... Layers of this type of solar cell are: 1-TCO made of ZnO (zinc oxide) 2- CdS layer gate. (cadmium sulphate) with impurities of n 3-CIGS absorber layer with the impurity of p, 4- 5 glass substrate molybdenum layer made of soda. Reduced thickness of the absorbent layer makes the back connection to be ...

  7. Expression of cbsA encoding the collagen-binding S-protein of Lactobacillus crispatus JCM5810 in Lactobacillus casei ATCC 393T

    NARCIS (Netherlands)

    Martínez, B.; Sillanpää, J.; Smit, E.; Korhonen, T.K.; Pouwels, P.H.

    2000-01-01

    The cbsA gene encoding the collagen-binding S-layer protein of Lactobacillus crispatus JCM5810 was expressed in L. casei ATCC 393T. The S-protein was not retained on the surface of the recombinant bacteria but was secreted into the medium. By translational fusion of CbsA to the cell wall sorting

  8. Effect of Lactobacillus brevis ATCC 8287 as a feeding supplement on the performance and immune function of piglets

    Science.gov (United States)

    Lactobacillus brevis ATCC 8287, a surface (S-layer) strain, possesses a variety of functional properties that make it both a potential probiotic and a good vaccine vector candidate. With this in mind, our aim was to study the survival of L. brevis in the porcine gut and investigate the effect of th...

  9. The interior configuration of planet Mercury constrained by moment of inertia and planetary contraction

    NARCIS (Netherlands)

    Knibbe, J.S.; van Westrenen, W.

    2015-01-01

    This paper presents an analysis of present-day interior configuration models for Mercury considering cores of Fe-S or Fe-Si alloy, the latter possibly covered by a solid FeS layer, in light of the improved limit of planetary contraction of 7 km derived from MErcury Surface, Space ENvironment,

  10. Dielectric and photo-dielectric properties of TlGaSeS crystals

    Indian Academy of Sciences (India)

    Administrator

    A F QASRAWIa,b,*, SAMAH F ABU-ZAIDa, SALAM A GHANAMEHa and N M GASANLYc. aDepartment of Physics, Arab-American University, Jenin, West Bank, Palestine .... dance to Maxwell–Wagner model (Wagner 1973), a di- electric medium is assumed to be composed of conducting crystallites (TlGaSeS layers) ...

  11. Supramolecular polymers

    National Research Council Canada - National Science Library

    Ciferri, A

    2000-01-01

    ... to the new class of self-assembled polymers that undergo reversible growth by the formation of noncovalent bonds. This class (Part II) is wider than expected: not only mainchain assemblies of hydrogen-bonded repeating units, but also planar organization of S-layer proteins, micellar and related three-dimensional structures of blo...

  12. Immunity of Surface Layer Protein of Aeromonas ‎hydrophila in Rabbits

    Directory of Open Access Journals (Sweden)

    Lobna Adil Al-Noori

    2017-11-01

    Full Text Available In this study the Surface layer (S-layer protein was extracted from Aeromonas hydrophila bacteria ,the humoral immune response that induced by S-layer protein only or as adjuvant was investigated  by using 16 males New Zealand rabbits and divided into four groups, each group contained four rabbits, the first group was immunized with  S-layer protein only, the second group was immunized with heated killed antigen(HKAof Sallmonella typhi only, the third group was immunized with mixed antigens (S-layer+ HKA,while the fourth group considered as control group and immunized with normal saline. The HKA of S. typhi  was used to evaluate the efficiency of S-layer protein as adjuvant. After the immunization period, the humoral immune response was investigated by several tests include, tube agglutination test and passive agglutination test that used to detect the antibody titer. Biuret method was used to determine the total protein concentration in serum  samples and total protein concentration of secretory immunoglobulin that extracted form appendix samples. In addition the Radical Immunodiffution (RID  method was used to detect the concentration level of the IgG in serum samples. Moreover the concentration level of the CD4 in the serum samples was determined by enzyme linked immunosorbent assay (ELISA method .In all these tests the result revealed, both of S-layer protein only , HKA of only and mixed antigens(S-layer+ HKA were given significantly increased in comparison with control group at P<0.05. The result showed that the  concentration level of IgG with mean values (2365.5 , 3505 and 2916 mg/dl respectively  while the control group with mean value (1662mg/dl. In addition the concentration  level of CD4 molecule with mean values (9.37, 11.77 and 17.36 ng/ml respectively while the control group with mean value (6.91 ng/ml .The results showed that these three types of antigens induced the humoral immune response

  13. Homologs of the Rml Enzymes from Salmonella enterica Are Responsible for dTDP-β-l-Rhamnose Biosynthesis in the Gram-Positive Thermophile Aneurinibacillus thermoaerophilus DSM 10155

    Science.gov (United States)

    Graninger, Michael; Kneidinger, Bernd; Bruno, Katharina; Scheberl, Andrea; Messner, Paul

    2002-01-01

    The glycan chains of the surface layer (S-layer) glycoprotein from the gram-positive, thermophilic bacterium Aneurinibacillus (formerly Bacillus) thermoaerophilus strain DSM 10155 are composed of l-rhamnose- and d-glycero-d-manno-heptose-containing disaccharide repeating units which are linked to the S-layer polypeptide via core structures that have variable lengths and novel O-glycosidic linkages. In this work we investigated the enzymes involved in the biosynthesis of thymidine diphospho-l-rhamnose (dTDP-l-rhamnose) and their specific properties. Comparable to lipopolysaccharide O-antigen biosynthesis in gram-negative bacteria, dTDP-l-rhamnose is synthesized in a four-step reaction sequence from dTTP and glucose 1-phosphate by the enzymes glucose-1-phosphate thymidylyltransferase (RmlA), dTDP-d-glucose 4,6-dehydratase (RmlB), dTDP-4-dehydrorhamnose 3,5-epimerase (RmlC), and dTDP-4-dehydrorhamnose reductase (RmlD). The rhamnose biosynthesis operon from A. thermoaerophilus DSM 10155 was sequenced, and the genes were overexpressed in Escherichia coli. Compared to purified enterobacterial Rml enzymes, the enzymes from the gram-positive strain show remarkably increased thermostability, a property which is particularly interesting for high-throughput screening and enzymatic synthesis. The closely related strain A. thermoaerophilus L420-91T produces d-rhamnose- and 3-acetamido-3,6-dideoxy-d-galactose-containing S-layer glycan chains. Comparison of the enzyme activity patterns in A. thermoaerophilus strains DSM 10155 and L420-91T for l-rhamnose and d-rhamnose biosynthesis indicated that the enzymes are differentially expressed during S-layer glycan biosynthesis and that A. thermoaerophilus L420-91T is not able to synthesize dTDP-l-rhamnose. These findings confirm that in each strain the enzymes act specifically on S-layer glycoprotein glycan formation. PMID:12147463

  14. Evaluation of microbial diversity in the pilot-scale beer brewing process by culture-dependent and culture-independent method.

    Science.gov (United States)

    Takahashi, M; Kita, Y; Kusaka, K; Mizuno, A; Goto-Yamamoto, N

    2015-02-01

    In the brewing industry, microbial management is very important for stabilizing the quality of the product. We investigated the detailed microbial community of beer during fermentation and maturation, to manage beer microbiology in more detail. We brewed a beer (all-malt) and two beerlike beverages (half- and low-malt) in pilot-scale fermentation and investigated the microbial community of them using a next-generation sequencer (454 GS FLX titanium), quantitative PCR, flow cytometry and a culture-dependent method. From 28 to 88 genera of bacteria and from 9 to 38 genera of eukaryotic micro-organisms were detected in each sample. Almost all micro-organisms died out during the boiling process. However, bacteria belonging to the genera Acidovorax, Bacillus, Brevundimonas, Caulobacter, Chryseobacterium, Methylobacterium, Paenibacillus, Polaromonas, Pseudomonas, Ralstonia, Sphingomonas, Stenotrophomonas, Tepidimonas and Tissierella were detected at the early and middle stage of fermentation, even though their cell densities were low (below approx. 10(3) cells ml(-1) ) and they were not almost detected at the end of fermentation. We revealed that the microbial community of beer during fermentation and maturation is very diverse and several bacteria possibly survive during fermentation. In this study, we revealed the detailed microbial communities of beer using next-generation sequencing. Some of the micro-organisms detected in this study were found in beer brewing process for the first time. Additionally, the possibility of growth of several bacteria at the early and middle stage of fermentation was suggested. © 2014 The Society for Applied Microbiology.

  15. Efficacy of Various Chemical Disinfectants on Biofilms Formed in Spacecraft Potable Water System Component

    Science.gov (United States)

    Wong, Willy; Garcia, Veronica; Castro, Victoria; Ott, Mark; Duane

    2009-01-01

    As the provision of potable water is critical for successful habitation of the International Space Station (ISS), life support systems were installed in December 2008 to recycle both humidity from the atmosphere and urine to conserve available water in the vehicle. Pre-consumption testing from the dispensing needle at the Potable Water Dispenser (PWD) indicated that bacterial concentrations exceeded the current ISS specifications of 50 colony forming units (CFU) per ml. Subsequent investigations revealed that a corrugated stainless steel flex hose upstream of the dispensing needle in the PWD was filled with non-sterile water and left at room temperature for over one month before launch. To simulate biofilm formation that was suspected in the flight system, sterile flex hoses were seeded with a consortium of bacterial isolates previously recovered from other ISS water systems, which included Ralstonia pickettii, Burkholderia multivorans, Caulobacter vibrioides., and Cupriavidus pauculus. After 5 days of incubation, these hoses were challenged with various chemical disinfectants including hydrogen peroxide, colloidal silver, and buffered pH solutions to determine the ability of the disinfectants to decrease and maintain bacterial concentrations below ISS specifications. Disinfection efficacy over time was measured by collecting daily heterotrophic plate counts following exposure to the disinfectants. A single flush with either 6% hydrogen peroxide solution or a mixture of 3% hydrogen peroxide and 400 ppb colloidal silver effectively reduced the bacterial concentrations to less than 1 CFU/ml for a period of up to 2 months. Testing results indicated that hydrogen peroxide and mixtures of hydrogen peroxide and colloidal silver have tremendous potential as alternative disinfectants for ISS water systems.

  16. DGGE detection and screening of lignocellulolytic bacteria from the termite gut of Coptotermes formosanus

    Directory of Open Access Journals (Sweden)

    Mathew, G.M.

    2011-01-01

    Full Text Available Aims: Termites thrive in terrestrial ecosystems and play an important role in the bio-recycling of lignocellulose. The objective of this study is to isolate and detect bacteria from the termite gut of Coptotermes formosanus and to screen their various enzyme activities by qualitative methods. In addition, this study was aimed to isolate lignin and furfural tolerant strains for various industrial bioprocesses.Methodology and Results: In this study, 50 worker termites of Coptotermes formosanus were collected from dead trees, from a forest in Taichung, Taiwan in June 2008 and the composition of the microbial flora from the termite guts was analyzed by DGGE analysis. The results proved that anaerobic and facultatively anaerobic bacteria consisting of Acinetobacter, Bacteroides thetaiotaomicron, Escherichia coli, and Caulobacter readily existed in the guts of termites. Although the majority of these gut symbionts have not yet been cultivated or identified, some related bacteria were isolated. Two isolates 1-8 and 2-2 of Genus Bacillus, exhibited endocellulase, protease, lipase, amylase, peroxidase and lignin peroxidase activity. Under aerobic conditions, the growth density of isolate 1-8 cultured in 1000 ppm lignin containing MSM medium was two-folds higher than cultured in MSM medium without lignin. Furthermore, the isolate 1-8 was tolerant to 20 mM furfural supplemented in the MSM medium. HPLC analysis confirmed Bacillus isolate 1-8 could degrade up to 15 mM furfural.Conclusion, significance and impact of study: Hind gut bacteria from C. formosanus were detected by culture independent DGGE method. Also, Bacillus isolates 1-8 and 2-2 obtained by culture dependent methods could withstand higher concentration of furfural and as well as lignin. These isolates may be co-cultured with ethanologenic bacteria and be used as an industrial biocatalyst for biofuel production.

  17. Actinorhizal Alder Phytostabilization Alters Microbial Community Dynamics in Gold Mine Waste Rock from Northern Quebec: A Greenhouse Study.

    Directory of Open Access Journals (Sweden)

    Katrina L Callender

    Full Text Available Phytotechnologies are rapidly replacing conventional ex-situ remediation techniques as they have the added benefit of restoring aesthetic value, important in the reclamation of mine sites. Alders are pioneer species that can tolerate and proliferate in nutrient-poor, contaminated environments, largely due to symbiotic root associations with the N2-fixing bacteria, Frankia and ectomycorrhizal (ECM fungi. In this study, we investigated the growth of two Frankia-inoculated (actinorhizal alder species, A. crispa and A. glutinosa, in gold mine waste rock from northern Quebec. Alder species had similar survival rates and positively impacted soil quality and physico-chemical properties in similar ways, restoring soil pH to neutrality and reducing extractable metals up to two-fold, while not hyperaccumulating them into above-ground plant biomass. A. glutinosa outperformed A. crispa in terms of growth, as estimated by the seedling volume index (SVI, and root length. Pyrosequencing of the bacterial 16S rRNA gene for bacteria and the ribosomal internal transcribed spacer (ITS region for fungi provided a comprehensive, direct characterization of microbial communities in gold mine waste rock and fine tailings. Plant- and treatment-specific shifts in soil microbial community compositions were observed in planted mine residues. Shannon diversity and the abundance of microbes involved in key ecosystem processes such as contaminant degradation (Sphingomonas, Sphingobium and Pseudomonas, metal sequestration (Brevundimonas and Caulobacter and N2-fixation (Azotobacter, Mesorhizobium, Rhizobium and Pseudomonas increased over time, i.e., as plants established in mine waste rock. Acetate mineralization and most probable number (MPN assays showed that revegetation positively stimulated both bulk and rhizosphere communities, increasing microbial density (biomass increase of 2 orders of magnitude and mineralization (five-fold. Genomic techniques proved useful in

  18. Stored Canine Whole Blood Units: What is the Real Risk of Bacterial Contamination?

    Science.gov (United States)

    Miglio, A; Stefanetti, V; Antognoni, M T; Cappelli, K; Capomaccio, S; Coletti, M; Passamonti, F

    2016-11-01

    Bacterial contamination of whole blood (WB) units can result in transfusion-transmitted infection, but the extent of the risk has not been established and may be underestimated in veterinary medicine. To detect, quantify, and identify bacterial microorganisms in 49 canine WB units during their shelf life. Forty-nine healthy adult dogs. Forty-nine WB units were included in the study. Immediately after collection, 8 sterile samples from the tube segment line of each unit were aseptically collected and tested for bacterial contamination on days 0, 1, 7, 14, 21, 28, 35, and 42 of storage. A qPCR assay was performed on days 0, 21, and 35 to identify and quantify any bacterial DNA. On bacterial culture, 47/49 blood units were negative at all time points tested, 1 unit was positive for Enterococcus spp. on days 0 and 1, and 1 was positive for Escherichia coli on day 35. On qPCR assay, 26 of 49 blood units were positive on at least 1 time point and the bacterial loads of the sequences detected (Propionobacterium spp., Corynebacterium spp., Caulobacter spp., Pseudomonas spp., Enterococcus spp., Serratia spp., and Leucobacter spp.) were <80 genome equivalents (GE)/μL. Most of the organisms detected were common bacteria, not usually implicated in septic transfusion reactions. The very low number of GE detected constitutes an acceptable risk of bacterial contamination, indicating that WB units have a good sanitary shelf life during commercial storage. Copyright © 2016 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

  19. Anterior foregut microbiota of the glassy-winged sharpshooter explored using deep 16S rRNA gene sequencing from individual insects.

    Directory of Open Access Journals (Sweden)

    Elizabeth E Rogers

    Full Text Available The glassy-winged sharpshooter (GWSS is an invasive insect species that transmits Xylella fastidiosa, the bacterium causing Pierce's disease of grapevine and other leaf scorch diseases. X. fastidiosa has been shown to colonize the anterior foregut (cibarium and precibarium of sharpshooters, where it may interact with other naturally-occurring bacterial species. To evaluate such interactions, a comprehensive list of bacterial species associated with the sharpshooter cibarium and precibarium is needed. Here, a survey of microbiota associated with the GWSS anterior foregut was conducted. Ninety-six individual GWSS, 24 from each of 4 locations (Bakersfield, CA; Ojai, CA; Quincy, FL; and a laboratory colony, were characterized for bacteria in dissected sharpshooter cibaria and precibaria by amplification and sequencing of a portion of the 16S rRNA gene using Illumina MiSeq technology. An average of approximately 150,000 sequence reads were obtained per insect. The most common genus detected was Wolbachia; sequencing of the Wolbachia ftsZ gene placed this strain in supergroup B, one of two Wolbachia supergroups most commonly associated with arthropods. X. fastidiosa was detected in all 96 individuals examined. By multilocus sequence typing, both X. fastidiosa subspecies fastidiosa and subspecies sandyi were present in GWSS from California and the colony; only subspecies fastidiosa was detected in GWSS from Florida. In addition to Wolbachia and X. fastidiosa, 23 other bacterial genera were detected at or above an average incidence of 0.1%; these included plant-associated microbes (Methylobacterium, Sphingomonas, Agrobacterium, and Ralstonia and soil- or water-associated microbes (Anoxybacillus, Novosphingobium, Caulobacter, and Luteimonas. Sequences belonging to species of the family Enterobacteriaceae also were detected but it was not possible to assign these to individual genera. Many of these species likely interact with X. fastidiosa in the

  20. Autochthonous bioaugmentation with environmental samples rich in hydrocarbonoclastic bacteria for bench-scale bioremediation of oily seawater and desert soil.

    Science.gov (United States)

    Ali, Nedaa; Dashti, Narjes; Salamah, Samar; Al-Awadhi, Husain; Sorkhoh, Naser; Radwan, Samir

    2016-05-01

    Oil-contaminated seawater and desert soil batches were bioaugmented with suspensions of pea (Pisum sativum) rhizosphere and soil with long history of oil pollution. Oil consumption was measured by gas-liquid chromatography. Hydrocarbonoclastic bacteria in the bioremediation batches were counted using a mineral medium with oil vapor as a sole carbon source and characterized by their 16S ribosomal RNA (rRNA)-gene sequences. Most of the oil was consumed during the first 2-4 months, and the oil-removal rate decreased or ceased thereafter due to nutrient and oxygen depletion. Supplying the batches with NaNO3 (nitrogen fertilization) at a late phase of bioremediation resulted in reenhanced oil consumption and bacterial growth. In the seawater batches bioaugmented with rhizospheric suspension, the autochthonous rhizospheric bacterial species Microbacterium oxidans and Rhodococcus spp. were established and contributed to oil-removal. The rhizosphere-bioaugmented soil batches selectively favored Arthrobacter nitroguajacolicus, Caulobacter segnis, and Ensifer adherens. In seawater batches bioaugmented with long-contaminated soil, the predominant oil-removing bacterium was the marine species Marinobacter hydrocarbonoclasticus. In soil batches on the other hand, the autochthonous inhabitants of the long-contaminated soil, Pseudomonas and Massilia species were established and contributed to oil removal. It was concluded that the use of rhizospheric bacteria for inoculating seawater and desert soil and of bacteria in long-contaminated soil for inoculating desert soil follows the concept of "autochthonous bioaugmentation." Inoculating seawater with bacteria in long-contaminated soil, on the other hand, merits the designation "allochthonous bioaugmentation."

  1. Protein O-glucosylation in Lactobacillus buchneri.

    Science.gov (United States)

    Anzengruber, Julia; Pabst, Martin; Neumann, Laura; Sekot, Gerhard; Heinl, Stefan; Grabherr, Reingard; Altmann, Friedrich; Messner, Paul; Schäffer, Christina

    2014-02-01

    Based on the previous demonstration of surface (S-) layer protein glycosylation in Lactobacillus buchneri 41021/251 and because of general advantages of lactic acid bacteria for applied research, protein glycosylation in this bacterial species was investigated in detail. The cell surface of L. buchneri CD034 is completely covered with an oblique 2D crystalline array (lattice parameters, a = 5.9 nm; b = 6.2 nm; γ ~ 77°) formed by self-assembly of the S-layer protein SlpB. Biochemical and mass spectrometric analyses revealed that SlpB is the most abundant protein and that it is O-glycosylated at four serine residues within the sequence S(152)-A-S(154)-S(155)-A-S(157) with, on average, seven Glc(α1-6) residues, each. Subcellular fractionation of strain CD034 indicated a sequential order of SlpB export and glucosylation as evidenced by lack of glucosylation of cytosolic SlpB. Protein glycosylation analysis was extended to strain L. buchneri NRRL B-30929 where an analogous glucosylation scenario could be detected, with the S-layer glycoprotein SlpN containing an O-glycosylation motif identical to that of SlpB. This corroborates previous data on S-layer protein glucosylation of strain 41021/251 and let us propose a species-wide S-layer protein O-glucosylation in L. buchneri targeted at the sequence motif S-A-S-S-A-S. Search of the L. buchneri genomes for the said glucosylation motif revealed one further ORF, encoding the putative glycosyl-hydrolase LbGH25B and LbGH25N in L. buchneri CD034 and NRRL B-30929, respectively, for which we have indications of a glycosylation comparable to that of the S-layer proteins. These findings demonstrate the presence of a distinct protein O-glucosylation system in Gram-positive and beneficial microbes.

  2. [Biological properties of Lactobacillus surface proteins].

    Science.gov (United States)

    Buda, Barbara; Dylus, Ewa; Górska-Frączek, Sabina; Brzozowska, Ewa; Gamian, Andrzej

    2013-04-04

    Lactobacillus, a genus of Gram-positive bacteria, includes many strains of probiotic microflora. Probiotics, by definition, are living microorganisms that exert beneficial effects on the host organism. The morphology and physiology of the Lactobacillus bacterial genus are described. The structure of the cell wall of Gram-positive bacteria is discussed. The surface S-layer of Lactobacillus composed of proteins (SLP) with low molecular mass is presented. Cell surface proteins participating in the regulation of growth and survival of the intestinal epithelium cells are characterized. The influence of stress factors such as increased temperature, pH, and enzymes of gastric and pancreatic juice on SLP expression is described. The ability of binding of heavy metal ions by S-layer proteins is discussed. The characteristics of these structures, including the ability to adhere to epithelial cells, and the inhibition of invasion of pathogenic microflora of type Shigella, Salmonella, Escherichia coli and Clostridium and their toxins, are presented. 

  3. Characterization of CdS thin films electrodeposited by an alternating current electrolysis method

    International Nuclear Information System (INIS)

    Fatas, E.; Herrasti, P.; Arjona, F.; Camarero, E.G.

    1986-01-01

    Conventional electrochemical methods of making CdS films are anodic oxidation of cadmium in a solution containing sulfide ions, and cathodic reduction from solutions containing soluble metal and sulfur compounds. In this paper a method is presented in which a CdS layer is deposited by a.c. electrolysis. The substrate is a glass plate covered by a layer of tin oxide. The electrolyte is an aqueous solution containing cadmium sulphate, ammonium sulphate, sodium thiosulphate, sodium chloride and glycerol. The applied a.c. voltages correspond to symmetrical and asymmetrical rectangular waves. During the electrolysis two electrodes are alternately connected to positive and negative potentials. As a result, Cd/sup 2+/ and S/sup 2-/ particles deposit at each electrode by turns, which results in the formation of a CdS layer

  4. Comparison of dayside current layers in Venus' ionosphere and earth's equatorial electrojet

    Science.gov (United States)

    Cole, Keith D.

    1993-01-01

    The major physical aspects of the equatorial electrojet of Earth and the dayside ionospheric current layers of Venus are compared, viz., the electric current intensity and total current, roles of electric field, pressure and gravity, diffusion time scales, and the Bernouille effect. The largest potential differences, of the order of 10 volts, horizontally across the dayside ionosphere of Venus, have important implications for possible dynamo action in the Venus ionosphere and the application of an electric field from the lower atmosphere or from the solar wind. An upper limit to the horizontal scale of vertical magnetic fields in the Venus ionosphere is estimated thereby for the first time. New upper limits on the velocity in, and thickness of, a possible S layer at Venus are presented. If an S layer exists, it is only for extreme conditions of the solar wind. A mechanism for formation of magnetic ropes in the Venus ionosphere is also proposed.

  5. On the Mysterious Propulsion of Synechococcus

    Science.gov (United States)

    Ehlers, Kurt; Oster, George

    2012-01-01

    We propose a model for the self-propulsion of the marine bacterium Synechococcus utilizing a continuous looped helical track analogous to that found in Myxobacteria [1]. In our model cargo-carrying protein motors, driven by proton-motive force, move along a continuous looped helical track. The movement of the cargo creates surface distortions in the form of small amplitude traveling ridges along the S-layer above the helical track. The resulting fluid motion adjacent to the helical ribbon provides the propulsive thrust. A variation on the helical rotor model of [1] allows the motors to be anchored to the peptidoglycan layer, where they drive rotation of the track creating traveling helical waves along the S-layer. We derive expressions relating the swimming speed to the amplitude, wavelength, and velocity of the surface waves induced by the helical rotor, and show that they fall in reasonable ranges to explain the velocity and rotation rate of swimming Synechococcus. PMID:22567124

  6. Investigation of metal sorption behavior of Slp1 from Lysinibacillus sphaericus JG-B53: a combined study using QCM-D, ICP-MS and AFM.

    Science.gov (United States)

    Suhr, Matthias; Unger, Nancy; Viacava, Karen E; Günther, Tobias J; Raff, Johannes; Pollmann, Katrin

    2014-12-01

    Surface layer proteins (S-layer) of Lysinibacillus sphaericus JG-B53 are biological compounds with several bio-based technical applications such as biosorptive materials for metal removal or rare metals recovery from the environment. Despite their well-described applications, a deeper understanding of their metal sorption behavior still remains challenging. The metal sorption ability of Au(3+), Pd(2+), Pt(2+) and Eu(3+) was investigated by ICP-MS, AFM and QCM-D which enables the sorption detection in real-time during in situ experiments. Results indicate a high binding of Pd, followed by Au, Eu and Pt to the proteins. The comparison between different methods allowed a deeper understanding of the metal sorption of isolated S-layer either frees in liquid, adsorbed forming a protein layer or as the bacteria surface.

  7. Exo- and surface proteomes of the probiotic bacterium Lactobacillus acidophilus NCFM

    DEFF Research Database (Denmark)

    Celebioglu, Hasan Ufuk; Svensson, Birte

    2017-01-01

    Lactobacillus acidophilus NCFM is a well-known probiotic bacterium extensively studied for its beneficial health effects. Exoproteome (proteins exported into culture medium) and surface proteome (proteins attached to S-layer) of this probiotic were identified by using 2DE followed by MALDI TOF MS......-classically secreted proteins. Identification of exo- and surface proteomes contributes describing potential protein-mediated probiotic-host interactions....

  8. Molecular beam epitaxial growth and structural characterization of ZnS on (001) GaAs

    Science.gov (United States)

    Benz, R. G., II; Huang, P. C.; Stock, S. R.; Summers, C. J.

    1988-01-01

    The effect of surface nucleation processes on the quality of ZnS layers grown on (001) GaAs substrates by molecular beam epitaxy is reported. Reflection high energy electron diffraction indicated that nucleation at high temperatures produced more planar surfaces than nucleation at low temperatures, but the crystalline quality as assessed by X-ray double crystal diffractometry is relatively independent of nucleation temperature. A critical factor in layer quality was the initial roughness of the GaAs surfaces.

  9. Operational Manning Considerations for Spartan Scout and Sea Fox Unmanned Surface Vehicles (USV)

    Science.gov (United States)

    2006-09-01

    library information resources on the topic. • An analysis of LCS manpower requirements concerning USV’s. • A qualitative analysis of U.S. Navy standards...mission areas are assigned: AAW AMW ASU ASW CCC C2W FSO INT MIW MOB MOS NCO STW P P P P P P S S S...USVs. The replacement of the Navy standard RHIB with a USV will enhance a ship’s layered defense architecture and provide the resource sponsor a

  10. Fabrication and electrical characterization of PbS-EuS ferromagnetic semiconductor microstructures

    International Nuclear Information System (INIS)

    Wrotek, S.; Morawski, A.; Tkaczyk, Z.

    2004-01-01

    Current-voltage characteristics and temperature dependence of differential conductance were studied in lithographically patterned (lateral dimensions from 10x10 μm 2 to 100x100 μm 3 ) ferromagnetic EuS-PbS-EuS microstructures. Below the ferromagnetic transmission temperature a 4% decrease in the structure conductance was observed for mutual antiferromagnetic orientation of magnetization vectors of ferromagnetic EuS layers. (author)

  11. Strategies for Competition Beyond Open Architecture (OA): Acquisition at the Edge of Chaos

    Science.gov (United States)

    2014-11-08

    well-defined open standards and platforms, such as Internet Protocol Version 4 ( IPV4 ) and associated Internet transport and application layer...protocols. Especially, IPV4 became emergent as the waist (i.e., the passing tube) of the layered hourglass business/technical architecture, as shown in...that IPV4 will stay forever. Evolutionary force has and will continue to evolve the Internet’s layered hourglass architecture. Figure 7. An

  12. Efficient multimedia data storage in cloud environment

    OpenAIRE

    Deshpande, Prachi; Sharma, S. C.; Peddoju, Sateesh K.; Abraham, Ajith

    2015-01-01

    With the rapid adoption of social media, people are more habituated to utilize the images and video for expressing themselves. Future communication will replace the conventional means of social interaction with the video or images. This, in turn, requires huge data storage and processing power. This paper reports a compression/decompression module for image and video sequences for the cloud computing environment. The reported mechanism acts as a submodule of IaaS layer of the clou...

  13. Influence of different geological structures on stress–strain state of hard rock mass

    Science.gov (United States)

    Kuznetzov, NN; Fedotova, YuV

    2018-03-01

    The results of numerical simulation of stress–strain state in a hard rock mass area with the complex geological structures are presented. The variants of the stress value change are considered depending on the boundary conditions and physical properties of the model blocks. Furthermore, the possibility of in-situ stress formation under the influence of energy coming from the deeper Earth’s layers is demonstrated in terms of the Khibiny Massif.

  14. An optimized efficient dual junction InGaN/CIGS solar cell: A numerical simulation

    Science.gov (United States)

    Farhadi, Bita; Naseri, Mosayeb

    2016-08-01

    The photovoltaic performance of an efficient double junction InGaN/CIGS solar cell including a CdS antireflector top cover layer is studied using Silvaco ATLAS software. In this study, to gain a desired structure, the different design parameters, including the CIGS various band gaps, the doping concentration and the thickness of CdS layer are optimized. The simulation indicates that under current matching condition, an optimum efficiency of 40.42% is achieved.

  15. Activity of lysozyme on Lactobacillus hilgardii strains isolated from Port wine.

    Science.gov (United States)

    Dias, Rita; Vilas-Boas, Eduardo; Campos, Francisco M; Hogg, Tim; Couto, José António

    2015-08-01

    This work evaluated the effect of lysozyme on lactobacilli isolated from Port wine. Bacterial growth experiments were conducted in MRS/TJ medium and inactivation studies were performed in phosphate buffer (KH2PO4), distilled water and wine supplemented with different concentrations of lysozyme. The response of bacteria to lysozyme was found to be highly strain dependent. Some strains of Lactobacillus hilgardii together with Lactobacillus collinoides and Lactobacillus fructivorans were found to be resistant to concentrations of lysozyme as high as 2000 mg/L. It was observed that among the L. hilgardii taxon the resistant strains possess an S-layer coat. Apparently, the strains of L. collinoides and L. fructivorans studied are also S-layer producers as suggested by the total protein profile obtained by SDS-PAGE. Thus, the hypothetical protective role of the S-layer against the action of lysozyme was investigated. From the various treatments used to remove the protein from the surface of the cells, the one employing LiCl (5 M) was the most effective. LiCl pre-treated cells exposed to lysozyme (2000 mg/L) in KH2PO4 buffer maintained its resistance. However, when cells were suspended in distilled water an increased sensitivity to lysozyme was observed. Moreover, it was found that the addition of ethanol (20% v/v) to the suspension medium (distilled water) triggered a strong inactivation effect especially on cells previously treated with LiCl (reduction of >6 CFU log cycles). The results suggest that the S-layer exerts a protective effect against lysozyme and that the cell suspension medium influences the bacteriolysis efficiency. It was also noted that ethanol enhances the inactivation effect of lysozyme. Copyright © 2015 Elsevier Ltd. All rights reserved.

  16. Luminescence properties of blue-red emitting multilayer coated single structure ZnS/MnS/ZnS nanocomposites.

    Science.gov (United States)

    Viswanath, R; Bhojya Naik, H S; Yashavanth Kumar, G S; Prashanth Kumar, P N; Harish, K N; Prabhakara, M C

    2014-05-05

    Uncoated ZnS, MnS and ZnS/MnS/ZnS nanocomposites were successfully synthesized by chemical co-precipitation method in air atmosphere by varying the thicknesses of MnS layer. Characterization techniques such as X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), UV-visible absorption and photoluminescence (PL) spectroscopy were used to characterize the novel ZnS/MnS/ZnS nanocomposites. The obtained particles were highly crystalline and monodispersed with an average particles size of 4.5-6.5 nm. The room temperature photoluminescence (PL) study of ZnS/MnS/ZnS nanocomposites showed an enhanced intensity with different concentration of manganese acetate. The presences of MnS layer in the nanocomposite have tuned the PL emission in the IR region. Addition of manganese acetate (0.1-0.4 M) in the nanocomposite showed a distinct PL emission peak centered at 740 nm i.e. in the red region with significant red shift. The PL emission of ZnS and MnS were tuned in the nonvisible IR region. It is shown that the variation in thickness of MnS layer leads to an enhanced photoluminescence intensity/efficiency of ZnS/MnS/ZnS nanocomposites. Copyright © 2014 Elsevier B.V. All rights reserved.

  17. [Construction and analysis of a monitoring system with remote real-time multiple physiological parameters based on cloud computing].

    Science.gov (United States)

    Zhu, Lingyun; Li, Lianjie; Meng, Chunyan

    2014-12-01

    There have been problems in the existing multiple physiological parameter real-time monitoring system, such as insufficient server capacity for physiological data storage and analysis so that data consistency can not be guaranteed, poor performance in real-time, and other issues caused by the growing scale of data. We therefore pro posed a new solution which was with multiple physiological parameters and could calculate clustered background data storage and processing based on cloud computing. Through our studies, a batch processing for longitudinal analysis of patients' historical data was introduced. The process included the resource virtualization of IaaS layer for cloud platform, the construction of real-time computing platform of PaaS layer, the reception and analysis of data stream of SaaS layer, and the bottleneck problem of multi-parameter data transmission, etc. The results were to achieve in real-time physiological information transmission, storage and analysis of a large amount of data. The simulation test results showed that the remote multiple physiological parameter monitoring system based on cloud platform had obvious advantages in processing time and load balancing over the traditional server model. This architecture solved the problems including long turnaround time, poor performance of real-time analysis, lack of extensibility and other issues, which exist in the traditional remote medical services. Technical support was provided in order to facilitate a "wearable wireless sensor plus mobile wireless transmission plus cloud computing service" mode moving towards home health monitoring for multiple physiological parameter wireless monitoring.

  18. The structure of the cysteine protease and lectin-like domains of Cwp84, a surface layer-associated protein from Clostridium difficile

    Energy Technology Data Exchange (ETDEWEB)

    Bradshaw, William J. [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Kirby, Jonathan M. [Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Thiyagarajan, Nethaji [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Chambers, Christopher J.; Davies, Abigail H. [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom); Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Roberts, April K.; Shone, Clifford C. [Public Health England, Porton Down, Salisbury SP4 0JG (United Kingdom); Acharya, K. Ravi, E-mail: bsskra@bath.ac.uk [University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)

    2014-07-01

    The crystal structure of Cwp84, an S-layer protein from Clostridium difficile is presented for the first time. The cathepsin L-like fold of cysteine protease domain, a newly observed ‘lectin-like’ domain and several other features are described. Clostridium difficile is a major problem as an aetiological agent for antibiotic-associated diarrhoea. The mechanism by which the bacterium colonizes the gut during infection is poorly understood, but undoubtedly involves a myriad of components present on the bacterial surface. The mechanism of C. difficile surface-layer (S-layer) biogenesis is also largely unknown but involves the post-translational cleavage of a single polypeptide (surface-layer protein A; SlpA) into low- and high-molecular-weight subunits by Cwp84, a surface-located cysteine protease. Here, the first crystal structure of the surface protein Cwp84 is described at 1.4 Å resolution and the key structural components are identified. The truncated Cwp84 active-site mutant (amino-acid residues 33–497; C116A) exhibits three regions: a cleavable propeptide and a cysteine protease domain which exhibits a cathepsin L-like fold followed by a newly identified putative carbohydrate-binding domain with a bound calcium ion, which is referred to here as a lectin-like domain. This study thus provides the first structural insights into Cwp84 and a strong base to elucidate its role in the C. difficile S-layer maturation mechanism.

  19. Functional Identification and Structure Determination of Two Novel Prolidases from cog1228 in the Amidohydrolase Superfamily

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, Dao Feng; Patskovsky, Yury; Xu, Chengfu; Fedorov, Alexander A.; Fedorov, Elena V.; Sisco, Abby A.; Sauder, J. Michael; Burley, Stephen K.; Almo, Steven C.; Raushel, Frank M. (Einstein); (TAM); (Lilly)

    2010-12-07

    Two uncharacterized enzymes from the amidohydrolase superfamily belonging to cog1228 were cloned, expressed, and purified to homogeneity. The two proteins, Sgx9260c (gi|44242006) and Sgx9260b (gi|44479596), were derived from environmental DNA samples originating from the Sargasso Sea. The catalytic function and substrate profiles for Sgx9260c and Sgx9260b were determined using a comprehensive library of dipeptides and N-acyl derivative of L-amino acids. Sgx9260c catalyzes the hydrolysis of Gly-L-Pro, L-Ala-L-Pro, and N-acyl derivatives of L-Pro. The best substrate identified to date is N-acetyl-L-Pro with a value of k{sub cat}/K{sub m} of 3 x 10{sup 5} M{sup -1} s{sup -1}. Sgx9260b catalyzes the hydrolysis of L-hydrophobic L-Pro dipeptides and N-acyl derivatives of L-Pro. The best substrate identified to date is N-propionyl-L-Pro with a value of k{sub cat}/K{sub m} of 1 x 10{sup 5} M{sup -1} s{sup -1}. Three-dimensional structures of both proteins were determined by X-ray diffraction methods (PDB codes 3MKV and 3FEQ). These proteins fold as distorted ({beta}/{alpha})8-barrels with two divalent cations in the active site. The structure of Sgx9260c was also determined as a complex with the N-methylphosphonate derivative of L-Pro (PDB code 3N2C). In this structure the phosphonate moiety bridges the binuclear metal center, and one oxygen atom interacts with His-140. The {alpha}-carboxylate of the inhibitor interacts with Tyr-231. The proline side chain occupies a small substrate binding cavity formed by residues contributed from the loop that follows {beta}-strand 7 within the ({beta}/{alpha})8-barrel. A total of 38 other proteins from cog1228 are predicted to have the same substrate profile based on conservation of the substrate binding residues. The structure of an evolutionarily related protein, Cc2672 from Caulobacter crecentus, was determined as a complex with the N-methylphosphonate derivative of L-arginine (PDB code 3MTW).

  20. Health-promoting properties exhibited by Lactobacillus helveticus strains.

    Science.gov (United States)

    Skrzypczak, Katarzyna; Gustaw, Waldemar; Waśko, Adam

    2015-01-01

    Many strains belonging to lactobacilli exert a variety of beneficial health effects in humans and some of the bacteria are regarded as probiotic microorganisms. Adherence and capabilities of colonization by Lactobacillus strains of the intestinal tract is a prerequisite for probiotic strains to exhibit desired functional properties. The analysis conducted here aimed at screening strains of Lactobacillus helveticus possessing a health-promoting potential. The molecular analysis performed, revealed the presence of a slpA gene encoding the surface S-layer protein SlpA (contributing to the immunostimulatory activity of L. helveticus M 92 probiotic strain) in all B734, DSM, T80, and T105 strains. The product of gene amplification was also identified in a Bifidobacterium animalis ssp. lactis BB12 probiotic strain. SDS-PAGE of a surface protein extract demonstrated the presence of a protein with a mass of about 50 kDa in all strains, which refers to the mass of the S-layer proteins. These results are confirmed by observations carried with transmission electron microscopy, where a clearly visible S-layer was registered in all the strains analyzed. The in vitro study results obtained indicate that the strongest adhesion capacity to epithelial cells (HT-29) was demonstrated by L. helveticus B734, while coaggregation with pathogens was highly diverse among the tested strains. The percentage degree of coaggregation was increasing with the incubation time. After 5 h of incubation, the strongest ability to coaggregate with Escherichia coli was expressed by T104. The T80 strain demonstrated a significant ability to co-aggregate with Staphylococcus aureus, while DSM with Bacillus subtilis. For B734, the highest values of co-aggregation coefficient was noted in samples with Salmonella. The capability of autoaggregation, antibiotic susceptibility, resistance to increasing salt concentrations, and strain survival in simulated small intestinal juice were also analyzed.

  1. Studies of CdS/CdTe interface: Comparison of CdS films deposited by close space sublimation and chemical bath deposition techniques

    International Nuclear Information System (INIS)

    Han, Jun-feng; Fu, Gan-hua; Krishnakumar, V.; Schimper, Hermann-Josef; Liao, Cheng; Jaegermann, Wolfram; Besland, M.P.

    2015-01-01

    The CdS layers were deposited by two different methods, close space sublimation (CSS) and chemical bath deposition (CBD) technique. The CdS/CdTe interface properties were investigated by transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed a large CSS-CdS grain size in the range of 70-80 nm. The interface between CSS-CdS and CdTe were clear and sharp, indicating an abrupt hetero-junction. On the other hand, CBD-CdS layer had much smaller grain size in the 5-10 nm range. The interface between CBD-CdS and CdTe was not as clear as CSS-CdS. With the stepwise coverage of CdTe layer, the XPS core levels of Cd 3d and S 2p in CSS-CdS had a sudden shift to lower binding energies, while those core levels shifted gradually in CBD-CdS. In addition, XPS depth profile analyses indicated a strong diffusion in the interface between CBD-CdS and CdTe. The solar cells prepared using CSS-CdS yielded better device performance than the CBD-CdS layer. The relationships between the solar cell performances and properties of CdS/CdTe interfaces were discussed. - Highlights: • Studies of CdS deposited by close space sublimation and chemical bath deposition • An observation of CdS/CdTe interface by transmission electron microscope • A careful investigation of CdS/CdTe interface by X ray photoelectron spectra • An easier diffusion at the chemical bath deposition CdS and CdTe interface

  2. Aquatic Nutrient Simulation Modules (NSMs) Developed for Hydrologic and Hydraulic Models

    Science.gov (United States)

    2016-02-01

    sediment SO4 in layers 1 and 2 can be written as = dt dSOh 11 4 (5.55a) 12 01 1 2 ,21 2 ,2 2 )()(5.0 STH K fvfv K DO L phpshdhdsh SsH TT + + H2S...layer 1, (5.61a) 12 01 1 2 ,21 2 ,2 2 )()(5.0 STH K fvfv K DO L phpshdhdsh SsH TT + − H2S oxidation in layer 1 (CSODH2S), ( )12122212 STHfSTHf phph

  3. Non-exponential resistive switching in Ag2S memristors: a key to nanometer-scale non-volatile memory devices.

    Science.gov (United States)

    Gubicza, Agnes; Csontos, Miklós; Halbritter, András; Mihály, György

    2015-03-14

    The dynamics of resistive switchings in nanometer-scale metallic junctions formed between an inert metallic tip and an Ag film covered by a thin Ag2S layer are investigated. Our thorough experimental analysis and numerical simulations revealed that the resistance change upon a switching bias voltage pulse exhibits a strongly non-exponential behaviour yielding markedly different response times at different bias levels. Our results demonstrate the merits of Ag2S nanojunctions as nanometer-scale non-volatile memory cells with stable switching ratios, high endurance as well as fast response to write/erase, and an outstanding stability against read operations at technologically optimal bias and current levels.

  4. A morphological study of the sulfurisation of digenite to covellite using reflected polarised light microscopy

    DEFF Research Database (Denmark)

    Rask Møller Frøkiær, Heidi; Warner, Terence E.

    2017-01-01

    A series of copper rods were reacted with sulfur vapour in evacuated glass ampoules at ∼445 °C. Product materials were characterised by powder X-ray diffraction and reflected polarised light microscopy. Copper sulfurised rapidly to digenite, γ-Cu2-xS, under these conditions, whereas the subsequent...... − besides being a p-type metal − is ionically conducting at 445 °C, although considerably less so than digenite. We infer that the growth of platy covellite crystals and their radial alignment in the primary CuS layer are a consequence of copper ion mobility being restricted to the basal plane...

  5. Expression of cbsA Encoding the Collagen-Binding S-Protein of Lactobacillus crispatus JCM5810 in Lactobacillus casei ATCC 393T

    OpenAIRE

    Martínez, Beatriz; Sillanpää, Jouko; Smit, Egbert; Korhonen, Timo K.; Pouwels, Peter H.

    2000-01-01

    The cbsA gene encoding the collagen-binding S-layer protein of Lactobacillus crispatus JCM5810 was expressed in L. casei ATCC 393T. The S-protein was not retained on the surface of the recombinant bacteria but was secreted into the medium. By translational fusion of CbsA to the cell wall sorting signal of the proteinase, PrtP, of L. casei, CbsA was presented at the surface, rendering the transformants able to bind to immobilized collagens.

  6. CdS thin films obtained by thermal treatment of cadmium(II) complex precursor deposited by MAPLE technique

    International Nuclear Information System (INIS)

    Rotaru, Andrei; Mietlarek-Kropidlowska, Anna; Constantinescu, Catalin; Scarisoreanu, Nicu; Dumitru, Marius; Strankowski, Michal; Rotaru, Petre; Ion, Valentin; Vasiliu, Cristina; Becker, Barbara; Dinescu, Maria

    2009-01-01

    Thin films of [Cd{SSi(O-Bu t ) 3 }(S 2 CNEt 2 )] 2 , precursor for semiconducting CdS layers, were deposited on silicon substrates by Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique. Structural analysis of the obtained films by Fourier transform infrared spectroscopy (FTIR) confirmed the viability of the procedure. After the deposition of the coordination complex, the layers are manufactured by appropriate thermal treatment of the system (thin film and substrate), according to the thermal analysis of the compound. Surface morphology of the thin films was investigated by atomic force microscopy (AFM) and spectroscopic-ellipsometry (SE) measurements.

  7. Smart SOA platforms in cloud computing architectures

    CERN Document Server

    Exposito , Ernesto

    2014-01-01

    This book is intended to introduce the principles of the Event-Driven and Service-Oriented Architecture (SOA 2.0) and its role in the new interconnected world based on the cloud computing architecture paradigm. In this new context, the concept of "service" is widely applied to the hardware and software resources available in the new generation of the Internet. The authors focus on how current and future SOA technologies provide the basis for the smart management of the service model provided by the Platform as a Service (PaaS) layer.

  8. Improve the performance of CZTSSe solar cells by applying a SnS BSF layer

    Science.gov (United States)

    Omrani, Mir Kazem; Minbashi, Mehran; Memarian, Nafiseh; Kim, Dae-Hwan

    2018-03-01

    In this study, the CZTSSe (Cu2ZnSn(S,Se)4) solar cells, with Al/ZnO:Al/ZnO (i)/CdS/CZTSSe/Mo structure, have been simulated. The simulation results have been compared and validated with real experimental results. Next, suggestions for improving the performance of CZTSSe solar cell have been provided. A SnS layer has been used as back surface field (BSF) layer. Different physical parameters of SnS layer are investigated, and the optimum values are selected. It has been found that by inserting a BSF layer with optimum parameters, the efficiency of CZTSSe solar cell increases from 12.3% to 17.25% due to enhancement of both short-circuit current density (Jsc) and open circuit voltage (Voc). For this optimized cell structure, the maximum Jsc = 37.37 mA/cm2, Voc = 0.605 V, and fill factor = 76.28% are obtained under 1.5 AM illumination.

  9. Solar-driven hydrogen evolution using a CuInS2/CdS/ZnO heterostructure nanowire array as an efficient photoanode.

    Science.gov (United States)

    Choi, Youngwoo; Beak, Minki; Yong, Kijung

    2014-08-07

    Photoanodes prepared using CuInS2/CdS/ZnO nanowires were fabricated by a solution-based process for constructing a photo-driven hydrogen generation system. For efficient light harvesting and photoexcited charge collection, ZnO nanowire (NW) photoanode arrays were co-sensitized with CdS and CuInS2 (CIS). A CdS layer was deposited on the ZnO NW via successive ion layer adsorption and reaction (SILAR), and the CIS layer was prepared by depositing a molecular precursor solution onto the CdS/ZnO NW. The generated anodic photocurrent was increased with the subsequent deposition of the CIS and CdS layers. Ultraviolet photoelectron spectroscopy analysis revealed cascade type-II band alignments for the CIS/CdS/ZnO NW photoanodes, which enabled efficient electron collection. Our heterostructure photoelectrode has generated a greatly improved photocurrent density of 13.8 mA cm(-2) at 0.3 V vs. SCE under 1 sun illumination.

  10. Uncovering the role of the ZnS treatment in the performance of quantum dot sensitized solar cells.

    Science.gov (United States)

    Guijarro, Néstor; Campiña, José M; Shen, Qing; Toyoda, Taro; Lana-Villarreal, Teresa; Gómez, Roberto

    2011-07-07

    Among the third-generation photovoltaic devices, much attention is being paid to the so-called Quantum Dot sensitized Solar Cells (QDSCs). The currently poor performance of QDSCs seems to be efficiently patched by the ZnS treatment, increasing the output parameters of the devices, albeit its function remains rather unclear. Here new insights into the role of the ZnS layer on the QDSC performance are provided, revealing simultaneously the most active recombination pathways. Optical and AFM characterization confirms that the ZnS deposit covers, at least partially, both the TiO(2) nanoparticles and the QDs (CdSe). Photoanodes submitted to the ZnS treatment before and/or after the introduction of colloidal CdSe QDs were studied by electrochemical impedance spectroscopy, cyclic voltammetry and photocurrent experiments. The corresponding results prove that the passivation of the CdSe QDs rather than the blockage of the TiO(2) surface is the main factor leading to the efficiency improvement. In addition, a study of the ultrafast carrier dynamics by means of the Lens-Free Heterodyne Detection Transient Grating technique indicates that the ZnS shell also increases the rate of electron transfer. The dual role of the ZnS layer should be kept in mind in the quest for new modifiers for enhancing the performance of QDSCs. This journal is © the Owner Societies 2011

  11. Studying the superconductor-ferromagnet proximity effect with polarised neutron reflectometry

    Science.gov (United States)

    Satchell, Nathan; Cooper, Joshaniel; Kinane, Christy; Witt, James; Burnell, Gavin; Langridge, Sean

    At the interface between a superconductor (S) and ferromagnet (F), an inhomogeneity can convert singlet Cooper pairs into the (spin aligned) long ranged triplet component (LRTC). The manipulation of the LRTC forms the basis of the emerging field of super-spintronics. Several theoretical works predict modification to the local magnetic state inside the S layer with the inclusion of triplet Cooper pairs, however there are now several experimental observations which disagree on both the magnitude and direction of this induced moment (see for example and). Here we report on measurements of the proximity effect using polarised neutron reflectometry, a technique sensitive to changes in the total magnetisation of a S-F heterostructure. Our results suggest that a `smoking gun' direct signature of the LRTC is below the sensitivity of our technique, we are able to study the inverse effect namely a modification to the ferromagnetism by proximity to singlet superconductivity. These observations are supported by XMCD measurements showing changes to the Fe and Co below the S layer Tc.

  12. Comparative study of water and ammonia rinsing processes of potassium fluoride-treated Cu(In,Ga)Se2 thin film solar cells

    Science.gov (United States)

    Khatri, Ishwor; Shudo, Kosuke; Matsuura, Junpei; Sugiyama, Mutsumi; Nakada, Tokio

    2017-08-01

    In this work, potassium fluoride (KF)-treated Cu(In,Ga)Se2 (CIGS) thin films were rinsed in ammonia and water solutions before buffer layer (CdS) deposition and the effects of rinsing on photovoltaic properties were investigated. X-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS) measurements revealed that sodium atoms out-diffused at the surface region during KF deposition. Water and ammonia rinsing processes of KF-treated CIGS thin films reduced alkali metals from the surface. However, sodium at the Cu-depleted surface layer remained at a high concentration, suggesting the occupation of Cu vacancies with sodium atoms. On the other hand, ammonia rinsing removed the Cu-poor region from the surfaces of KF-treated CIGS thin films affecting the growth (or nucleation) of the CdS layer. The surface coverage of the CdS layer deposited on the ammonia-rinsed KF-treated CIGS thin film was inferior to than that of water-rinsed samples, resulting in the poor cell performance due to an increased interface recombination.

  13. Haloferax volcanii N-glycosylation: delineating the pathway of dTDP-rhamnose biosynthesis.

    Directory of Open Access Journals (Sweden)

    Lina Kaminski

    Full Text Available In the halophilic archaea Haloferax volcanii, the surface (S-layer glycoprotein can be modified by two distinct N-linked glycans. The tetrasaccharide attached to S-layer glycoprotein Asn-498 comprises a sulfated hexose, two hexoses and a rhamnose. While Agl11-14 have been implicated in the appearance of the terminal rhamnose subunit, the precise roles of these proteins have yet to be defined. Accordingly, a series of in vitro assays conducted with purified Agl11-Agl14 showed these proteins to catalyze the stepwise conversion of glucose-1-phosphate to dTDP-rhamnose, the final sugar of the tetrasaccharide glycan. Specifically, Agl11 is a glucose-1-phosphate thymidylyltransferase, Agl12 is a dTDP-glucose-4,6-dehydratase and Agl13 is a dTDP-4-dehydro-6-deoxy-glucose-3,5-epimerase, while Agl14 is a dTDP-4-dehydrorhamnose reductase. Archaea thus synthesize nucleotide-activated rhamnose by a pathway similar to that employed by Bacteria and distinct from that used by Eukarya and viruses. Moreover, a bioinformatics screen identified homologues of agl11-14 clustered in other archaeal genomes, often as part of an extended gene cluster also containing aglB, encoding the archaeal oligosaccharyltransferase. This points to rhamnose as being a component of N-linked glycans in Archaea other than Hfx. volcanii.

  14. Temperature- and excitation intensity-dependent photoluminescence in TlInSeS single crystals

    CERN Document Server

    Gasanly, N M; Yuksek, N S

    2002-01-01

    Photoluminescence (PL) spectra of TlInSeS layered single crystals were investigated in the wavelength region 460-800 nm and in the temperature range 10-65 K. We observed one wide PL band centred at 584 nm (2.122 eV) at T=10 K and an excitation intensity of 7.5 W cm sup - sup 2. We have also studied the variation of the PL intensity versus excitation laser intensity in the range from 0.023 to 7.5 W cm sup - sup 2. The red shift of this band with increasing temperature and blue shift with increasing laser excitation intensity was observed. The PL was found to be due to radiative transitions from the moderately deep donor level located at 0.243 eV below the bottom of the conduction band to the shallow acceptor level at 0.023 eV located above the top of the valence band. The proposed energy-level diagram permits us to interpret the recombination processes in TlInSeS layered single crystals.

  15. Biological properties of Lactobacillus surface proteins 

    Directory of Open Access Journals (Sweden)

    Barbara Buda

    2013-04-01

    Full Text Available Lactobacillus, a genus of Gram-positive bacteria, includes many strains of probiotic microflora. Probiotics, by definition, are living microorganisms that exert beneficial effects on the host organism. The morphology and physiology of the Lactobacillus bacterial genus are described. The structure of the cell wall of Gram-positive bacteria is discussed. The surface S-layer of Lactobacillus composed of proteins (SLP with low molecular mass is presented. Cell surface proteins participating in the regulation of growth and survival of the intestinal epithelium cells are characterized. The influence of stress factors such as increased temperature, pH, and enzymes of gastric and pancreatic juice on SLP expression is described. The ability of binding of heavy metal ions by S-layer proteins is discussed. The characteristics of these structures, including the ability to adhere to epithelial cells, and the inhibition of invasion of pathogenic microflora of type Shigella, Salmonella, Escherichia coli and Clostridium and their toxins, are presented. 

  16. The specificationof nano-structure superficial layers in some of the pathogen bacteria

    Directory of Open Access Journals (Sweden)

    Shilla Jalalpoor

    2010-11-01

    Full Text Available Background: The superficial layer is a part of the cellular envelop that is seen in bacteria and archaea. This superficial layer is a single layer structure composed of subordinate proteins or glycoproteins. The superficial layer is the outer most cellular structure that is in the exchange and reaction around environment with bacteria. This structure has very diversity in bacteria different types.Materials and Method: The related articles to superficial layer were extracted of these articles: Pubmed, Elsevier Science, and Yahoo, from 1995 to 2010 years. For this purpose keywords were searched including superficial layer, pathogenesis, pathogen bacteria,Results: There is consensus in the case of the superficial layer and about the existence of this superficial structure lead to increased pathogenesis in bacteria, in all of the research articles.Conclusion: S-layers in pathogen bacteria with bacteria protection against bacteriophages and phagocytosis, resistance against low pH, adhesion, stabilisation of the membrane and providing adhesion sites for exoproteins caused pathogenesis, infection resistant and antibiotic resistant in host.The result of this study shows the prevalence of considerable S-layer in pathogen bacteria and this matter identified the bacteria generator importance of this structure in the laboratory

  17. AglC and AglK are involved in biosynthesis and attachment of diacetylated glucuronic acid to the N-glycan in Methanococcus voltae.

    Science.gov (United States)

    Chaban, Bonnie; Logan, Susan M; Kelly, John F; Jarrell, Ken F

    2009-01-01

    Recent advances in the field of prokaryotic N-glycosylation have established a foundation for the pathways and proteins involved in this important posttranslational protein modification process. To continue the study of the Methanococcus voltae N-glycosylation pathway, characteristics of known eukaryotic, bacterial, and archaeal proteins involved in the N-glycosylation process were examined and used to select candidate M. voltae genes for investigation as potential glycosyl transferase and flippase components. The targeted genes were knocked out via linear gene replacement, and the resulting effects on N-glycan assembly were identified through flagellin and surface (S) layer protein glycosylation defects. This study reports the finding that deletion of two putative M. voltae glycosyl transferase genes, designated aglC (for archaeal glycosylation) and aglK, interfered with proper N-glycosylation. This resulted in flagellin and S-layer proteins with significantly reduced apparent molecular masses, loss of flagellar assembly, and absence of glycan attachment. Given previous knowledge of both the N-glycosylation pathway in M. voltae and the general characteristics of N-glycosylation components, it appears that AglC and AglK are involved in the biosynthesis or transfer of diacetylated glucuronic acid within the glycan structure. In addition, a knockout of the putative flippase candidate gene (Mv891) had no effect on N-glycosylation but did result in the production of giant cells with diameters three to four times that of wild-type cells.

  18. Microfabricated instruments and methods to treat recurrent corneal erosions

    Energy Technology Data Exchange (ETDEWEB)

    Britton, Jr., Charles L.; D' urso, Brian R.; Chaum, Edward; Simpson, John T.; Baba, Justin S.; Ericson, M. Nance; Warmack, Robert J.

    2015-06-02

    In one embodiment, the present invention provides a device and method for treating recurrent corneal erosion. In one embodiment, the method includes the steps of contacting an epithelium layer of a cornea with an array of glass micro-rods including a plurality of sharp features having a length that penetrates a Bowman's layer of the eye, wherein the plurality of sharp features of the array of glass micro-rods produces a plurality of punctures in the Bowman's layer of the eye that are of micro-scale or less. In another embodiment, the present invention provides a method and device for drug delivery. In one embodiment, the device includes an array of glass micro-rods, wherein at least one glass micro-rod of the array of glass micro-rods includes a sharp feature opposite a base of the array of glass micro-rods, wherein the sharp feature includes a treated surface for delivering a chemical compound to the eye.

  19. Molecular and Chemical Analysis of the Lipopolysaccharide from Aeromonas hydrophila Strain AH-1 (Serotype O11

    Directory of Open Access Journals (Sweden)

    Susana Merino

    2015-04-01

    Full Text Available A group of virulent Aeromonas hydrophila, A. sobria, and A. veronii biovar sobria strains isolated from humans and fish have been described; these strains classified to serotype O11 are serologically related by their lipopolysaccharide (LPS O-antigen (O-polysaccharide, and the presence of an S-layer consisting of multiple copies of a crystalline surface array protein with a molecular weight of 52 kDa in the form of a crystalline surface array which lies peripheral to the cell wall. A. hydrophila strain AH-1 is one of them. We isolated the LPS from this strain and determined the structure of the O-polysaccharide, which was similar to that previously described for another strain of serotype O11. The genetics of the O11-antigen showed the genes (wbO11 cluster in two sections separated by genes involved in biosynthesis and assembly of the S-layer. The O11-antigen LPS is an example of an ABC-2-transporter-dependent pathway for O-antigen heteropolysaccharide (disaccharide assembly. The genes involved in the biosynthesis of the LPS core (waaO11 cluster were also identified in three different chromosome regions being nearly identical to the ones described for A. hydrophila AH-3 (serotype O34. The genetic data and preliminary chemical analysis indicated that the LPS core for strain AH-1 is identical to the one for strain AH-3.

  20. On the mysterious propulsion of Synechococcus.

    Directory of Open Access Journals (Sweden)

    Kurt Ehlers

    Full Text Available We propose a model for the self-propulsion of the marine bacterium Synechococcus utilizing a continuous looped helical track analogous to that found in Myxobacteria [1]. In our model cargo-carrying protein motors, driven by proton-motive force, move along a continuous looped helical track. The movement of the cargo creates surface distortions in the form of small amplitude traveling ridges along the S-layer above the helical track. The resulting fluid motion adjacent to the helical ribbon provides the propulsive thrust. A variation on the helical rotor model of [1] allows the motors to be anchored to the peptidoglycan layer, where they drive rotation of the track creating traveling helical waves along the S-layer. We derive expressions relating the swimming speed to the amplitude, wavelength, and velocity of the surface waves induced by the helical rotor, and show that they fall in reasonable ranges to explain the velocity and rotation rate of swimming Synechococcus.

  1. Cu{sub 2−x}S films as counter-electrodes for dye solar cells with ferrocene-based liquid electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Congiu, M., E-mail: mirko.congiu@fc.unesp.br [UNESP, Univ. Estadual Paulista, POSMAT — Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Av. Eng. Luiz Edmundo Carrijo Coube14-01, 17033-360 Bauru, SP (Brazil); Nunes-Neto, O. [UNESP, Univ. Estadual Paulista, POSMAT — Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Av. Eng. Luiz Edmundo Carrijo Coube14-01, 17033-360 Bauru, SP (Brazil); De Marco, M.L.; Dini, D. [University of Rome “La Sapienza”, Department of Chemistry, Piazzale Aldo Moro 5, Rome, RM (Italy); Graeff, C.F.O. [UNESP, Univ. Estadual Paulista, POSMAT — Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, Av. Eng. Luiz Edmundo Carrijo Coube14-01, 17033-360 Bauru, SP (Brazil); DC-FC, UNESP, Univ. Estadual Paulista, Av. Eng. Luiz Edmundo Carrijo Coube14-01, 17033-360 Bauru, SP (Brazil)

    2016-08-01

    In this work, the application of hexagonal CuS nanoparticle layers as counter electrodes for dye sensitized solar cells has been studied. A fast, cheap and reliable deposition method was proposed for the one-step preparation of Cu{sub 2−x}S layers on F-doped SnO{sub 2} within 30 min through an ink-based technique. The electrodes prepared with our method were tested with iodine/iodide electrolyte, Co(II)/(III) bipyridine redox shuttle and Fe(II)/(III) ferrocene-based liquid electrolyte. The Cu{sub 2−x}S layers showed high efficiency and stability with the ferrocene/ferrocenium redox couple, showing a fast charge recombination kinetic, low charge transfer resistance (R{sub ct} = 0.73 Ω cm{sup 2}), reasonably high limiting current (11.8 mA cm{sup −2}) and high stability in propylene carbonate. - Highlights: • We proposed a low-cost Cu{sub 2−x}S electrode for dye solar cells. • Easy deposition and processing • Suitable for large-area applications • Advantages and limitations of Cu{sub 2−x}S with three different redox electrolytes • High electro-catalytic efficiency and stability with the ferrocene/ferrocenium redox couple.

  2. Energy filtering transmission electron microscopy immunocytochemistry and antigen retrieval of surface layer proteins from Tannerella forsythensis using microwave or autoclave heating with citraconic anhydride.

    Science.gov (United States)

    Moriguchi, K; Mitamura, Y; Iwami, J; Hasegawa, Y; Higuchi, N; Murakami, Y; Maeda, H; Yoshimura, F; Nakamura, H; Ohno, N

    2012-11-01

    Tannerella forsythensis (Bacteroides forsythus), an anaerobic Gram-negative species of bacteria that plays a role in the progression of periodontal disease, has a unique bacterial protein profile. It is characterized by two unique protein bands with molecular weights of more than 200 kDa. It also is known to have a typical surface layer (S-layer) consisting of regularly arrayed subunits outside the outer membrane. We examined the relationship between high molecular weight proteins and the S-layer using electron microscopic immunolabeling with chemical fixation and an antigen retrieval procedure consisting of heating in a microwave oven or autoclave with citraconic anhydride. Immunogold particles were localized clearly at the outermost cell surface. We also used energy-filtering transmission electron microscopy (EFTEM) to visualize 3, 3'-diaminobenzidine tetrahydrochloride (DAB) reaction products after microwave antigen retrieval with 1% citraconic anhydride. The three-window method for electron spectroscopic images (ESI) of nitrogen by the EFTEM reflected the presence of moieties demonstrated by the DAB reaction with horseradish peroxidase (HRP)-conjugated secondary antibodies instead of immunogold particles. The mapping patterns of net nitrogen were restricted to the outermost cell surface.

  3. Verification of antiferromagnetic exchange coupling at room temperature using polar magneto-optic Kerr effect in thin EuS/Co multilayers with perpendicular magnetic anisotropy

    Energy Technology Data Exchange (ETDEWEB)

    Goschew, A., E-mail: alexander.goschew@fu-berlin.de; Scott, M.; Fumagalli, P. [Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany)

    2016-08-08

    We report on magneto-optic Kerr measurements in polar geometry carried out on a series of thin Co/EuS multilayers on suitable Co/Pd-multilayer substrates. Thin Co/EuS multilayers of a few nanometers individual layer thickness usually have their magnetization in plane. Co/Pd multilayers introduce a perpendicular magnetic anisotropy in the Co/EuS layers deposited on top, thus making it possible to measure magneto-optic signals in the polar geometry in remanence in order to study exchange coupling. Magneto-optic Kerr-effect spectra and hysteresis loops were recorded in the visible and ultraviolet photon-energy range at room temperature. The EuS contribution to the magneto-optic signal is extracted at 4.1 eV by combining hysteresis loops measured at different photon energies with polar magneto-optic Kerr-effect spectra recorded in remanence and in an applied magnetic field of 2.2 T. The extracted EuS signal shows clear signs of antiferromagnetic coupling of the Eu magnetic moments to the Co layers. This implies that the ordering temperature of at least a fraction of the EuS layers is above room temperature proving that magneto-optic Kerr-effect spectroscopy can be used here as a quasi-element-specific method.

  4. Structure of corneal layers, collagen fibrils, and proteoglycans of tree shrew cornea

    Science.gov (United States)

    Almubrad, Turki

    2011-01-01

    Purpose The stroma is the major part of the cornea, in which collagen fibrils and proteoglycans are distributed uniformly. We describe the ultrastructure of corneal layers, collagen fibrils (CF), and proteoglycans (PGs) in the tree shrew cornea. Methods Tree shrew corneas (5, 6, and 10 week old animals) and normal human corneas (24, 25, and 54 years old) were fixed in 2.5% glutaraldehyde containing cuprolinic blue in a sodium acetate buffer. The tissue was processed for electron microscopy. The ‘iTEM Olympus Soft Imaging Solutions GmbH’ program was used to measure the corneal layers, collagen fibril diameters and proteoglycan areas. Results The tree shrew cornea consists of 5 layers: the epithelium, Bowman’s layer, stroma, Descemet’s membrane, and endothelium. The epithelium was composed of squamous cells, wing cells and basal cells. The Bowman’s layer was 5.5±1.0 µm thick and very similar to a normal human Bowman’s layer. The stroma was 258±7.00 µm thick and consisted of collagen fibril lamellae. The lamellae were interlaced with one another in the anterior stroma, but ran parallel to one another in the middle and posterior stroma. Collagen fibrils were decorated with proteoglycan filaments with an area size of 390 ±438 nm2. The collagen fibril had a minimum diameter of 39±4.25 nm. The interfibrillar spacing was 52.91±6.07 nm. Within the collagen fibrils, very small electron-dense particles were present. Conclusions The structure of the tree shrew cornea is very similar to that of the normal human cornea. As is the case with the human cornea, the tree shrew cornea had a Bowman's layer, lamellar interlacing in the anterior stroma and electron-dense particles within the collagen fibrils. The similarities of the tree shrew cornea with the human cornea suggest that it could be a good structural model to use when studying changes in collagen fibrils and proteoglycans in non-genetic corneal diseases, such as ectasia caused after LASIK (laser

  5. Microstructural characterization of chemical bath deposited and sputtered Zn(O,S) buffer layers

    International Nuclear Information System (INIS)

    Gautron, E.; Buffière, M.; Harel, S.; Assmann, L.; Arzel, L.; Brohan, L.; Kessler, J.; Barreau, N.

    2013-01-01

    The present work aims at investigating the microstructure of Zn(O,S) buffer layers relative to their deposition route, namely either chemical bath deposition (CBD) or RF co-sputtering process (PVD) under pure Ar. The core of the study consists of cross-sectional transmission electron microscopy (TEM) characterization of the differently grown Zn(O,S) thin films on co-evaporated Cu(In,Ga)Se 2 (CIGSe) absorbers. It shows that the morphology of Zn(O,S) layer deposited on CIGSe using CBD process is made of a thin layer of well oriented ZnS sphalerite-(111) and/or ZnS wurtzite-(0002) planes parallel to CIGSe chalcopyrite-(112) planes at the interface with CIGSe followed by misoriented nanometer-sized ZnS crystallites in an amorphous phase. As far as (PVD)Zn(O,S) is concerned, the TEM analyses reveal two different microstructures depending on the S-content in the films: for [S] / ([O] + [S]) = 0.6, the buffer layer is made of ZnO zincite and ZnS wurtzite crystallites grown nearly coherently to each other, with (0002) planes nearly parallel with CIGSe-(112) planes, while for [S] / ([O] + [S]) = 0.3, it is made of ZnO zincite type crystals with O atoms substituted by S atoms, with (0002) planes perfectly aligned with CIGSe-(112) planes. Such microstructural differences can explain why photovoltaic performances are dependent on the Zn(O,S) buffer layer deposition route. - Highlights: ► Zn(O,S) layers were grown by chemical bath (CBD) or physical vapor (PVD) deposition. ► For CBD, a 3 nm ZnS layer is followed by ZnS nano-crystallites in an amorphous phase. ► For PVD with [S] / ([O] + [S]) = 0.3, the layer has a Zn(O,S) zincite structure. ► For PVD with [S] / ([O] + [S]) = 0.6, ZnS wurtzite and ZnO zincite phases are mixed

  6. Morphological and structural aspects of the extremely halophilic archaeon Haloquadratum walsbyi.

    Directory of Open Access Journals (Sweden)

    Matilde Sublimi Saponetti

    Full Text Available Ultrathin square cell Haloquadratum walsbyi from the Archaea domain are the most abundant microorganisms in the hypersaline water of coastal salterns and continental salt lakes. In this work, we explore the cell surface of these microorganisms using amplitude-modulation atomic-force microscopy in nearly physiological conditions. We demonstrate the presence of a regular corrugation with a periodicity of 16-20 nm attributed to the surface layer (S-layer protein lattice, striped domains asymmetrically distributed on the cell faces and peculiar bulges correlated with the presence of intracellular granules. Besides, subsequent images of cell evolution during the drying process indicate the presence of an external capsule that might correspond to the giant protein halomucin, predicted by the genome but never before observed by other microscopy studies.

  7. Mannan-Degrading Enzymes from Cellulomonas fimi

    Science.gov (United States)

    Stoll, Dominik; Stålbrand, Henrik; Warren, R. Antony J.

    1999-01-01

    The genes man26a and man2A from Cellulomonas fimi encode mannanase 26A (Man26A) and β-mannosidase 2A (Man2A), respectively. Mature Man26A is a secreted, modular protein of 951 amino acids, comprising a catalytic module in family 26 of glycosyl hydrolases, an S-layer homology module, and two modules of unknown function. Exposure of Man26A produced by Escherichia coli to C. fimi protease generates active fragments of the enzyme that correspond to polypeptides with mannanase activity produced by C. fimi during growth on mannans, indicating that it may be the only mannanase produced by the organism. A significant fraction of the Man26A produced by C. fimi remains cell associated. Man2A is an intracellular enzyme comprising a catalytic module in a subfamily of family 2 of the glycosyl hydrolases that at present contains only mammalian β-mannosidases. PMID:10347049

  8. Investigation on Spin Dependent Transport Properties of Core-Shell Structural Fe3O4/ZnS Nanocomposites for Spintronic Application

    Science.gov (United States)

    Liu, Er; Yuan, Honglei; Kou, Zhaoxia; Wu, Xiumei; Xu, Qingyu; Zhai, Ya; Sui, Yunxia; You, Biao; Du, Jun; Zhai, Hongru

    2015-01-01

    The core-shell structural Fe3O4/ZnS nanocomposites with controllable shell thickness were well-fabricated via seed-mediate growth method. Structural and morphological characterizations reveal the direct deposition of crystalline II-VI compound semiconductor ZnS shell layer on Fe3O4 particles. Spin dependent electrical transport is studied on Fe3O4/ZnS nanocomposites with different shell thickness, and a large magnetoresistance (MR) ratio is observed under the magnetic field of 1.0 T at room temperature and 100 K for the compacted sample by Fe3O4/ZnS nanocomposites, which is 50% larger than that of sample with pure Fe3O4 particles, indicating that the enhanced MR is contributed from the spin injection between Fe3O4 and ZnS layer. PMID:26053888

  9. Conjugation by Mosquito Pathogenic Strains of Bacillus sphaericus

    Directory of Open Access Journals (Sweden)

    Margarita Correa

    1997-05-01

    Full Text Available A mosquito pathogenic strain of Bacillus sphaericus carried out the conjugal transfer of plasmid pAMß1 to other strains of its own and two other serotypes. However, it was unable to conjugate with mosquito pathogens from three other serotypes, with B. sphaericus of other DNA homology groups or with three other species of Bacillus. Conjugation frequency was highest with a strain having an altered surface layer (S layer. Conjugal transfer of pAMß1 was not detected in mosquito larval cadavers. B. sphaericus 2362 was unable to mobilize pUB110 for transfer to strains that had served as recipients of pAMß1. These observations suggest that it is unlikely that genetically engineered B. sphaericus carrying a recombinant plasmid could pass that plasmid to other bacteria

  10. CuGaS2 and CuGaS2–ZnS Porous Layers from Solution-Processed Nanocrystals

    Directory of Open Access Journals (Sweden)

    Taisiia Berestok

    2018-04-01

    Full Text Available The manufacturing of semiconducting films using solution-based approaches is considered a low cost alternative to vacuum-based thin film deposition strategies. An additional advantage of solution processing methods is the possibility to control the layer nano/microstructure. Here, we detail the production of mesoporous CuGaS2 (CGS and ZnS layers from spin-coating and subsequent cross-linking through chalcogen-chalcogen bonds of properly functionalized nanocrystals (NCs. We further produce NC-based porous CGS/ZnS bilayers and NC-based CGS–ZnS composite layers using the same strategy. Photoelectrochemical measurements are used to demonstrate the efficacy of porous layers, and particularly the CGS/ZnS bilayers, for improved current densities and photoresponses relative to denser films deposited from as-produced NCs.

  11. Planar heterojunction perovskite solar cell based on CdS electron transport layer

    KAUST Repository

    Abulikemu, Mutalifu

    2017-07-02

    We report on planar heterojunction perovskite solar cells employing a metal chalcogenide (CdS) electron transport layer with power conversion efficiency up to 10.8%. The CdS layer was deposited via solution-process chemical bath deposition at low-temperature (60°C). Pinhole-free and uniform thin films were obtained with good structural, optical and morphological properties. An optimal layer thickness of 60nm yielded an improved open-circuit voltage and fill factor compared to the standard TiO2-based solar cells. Devices showed a higher reproducibility of the results compared to TiO2-based ones. We also tested the effect of annealing temperature on the CdS film and the effect of CdCl2 treatment followed by high temperature annealing (410°C) that is expected to passivate the surface, thus eliminating eventual trap-states inducing recombination.

  12. The Prevalence of STIV c92-Like Proteins in Acidic Thermal Environments

    Directory of Open Access Journals (Sweden)

    Jamie C. Snyder

    2011-01-01

    Full Text Available A new type of viral-induced lysis system has recently been discovered for two unrelated archaeal viruses, STIV and SIRV2. Prior to the lysis of the infected host cell, unique pyramid-like lysis structures are formed on the cell surface by the protrusion of the underlying cell membrane through the overlying external S-layer. It is through these pyramid structures that assembled virions are released during lysis. The STIV viral protein c92 is responsible for the formation of these lysis structures. We searched for c92-like proteins in viral sequences present in multiple viral and cellular metagenomic libraries from Yellowstone National Park acidic hot spring environments. Phylogenetic analysis of these proteins demonstrates that, although c92-like proteins are detected in these environments, some are quite divergent and may represent new viral families. We hypothesize that this new viral lysis system is common within diverse archaeal viral populations found within acidic hot springs.

  13. Effects of annealing conditions of electrodes on the photovoltaic properties of sintered cadmium sulfide/cadmium telluride solar cells

    International Nuclear Information System (INIS)

    Kim, C.S.; Im, H.B.

    1990-01-01

    Polycrystalline n-CdS/p-CdTe solar cells with a commercial carbon paint on the p-CdTe layer and an In- Ag paint on the n-CdS layer were fabricated by a coating and sintering method. Electrical properties of the conducting paints and solar cell parameters of the heterojunction solar cells were investigated as a function of electrode annealing conditions. The sintered CdS/CdTe solar cells whose electrode contacts were annealed at 350 degrees C for 10 min in nitrogen showed maximum values of short-circuit current density, fill factor, and solar efficiency. Commercial carbon and silver paints can be used as electrodes to fabricate sintered CdS/CdTe solar cells with efficiency over 10%

  14. Migration of Te atoms and structural changes in CdS/CdTe heterojuctions studied by x-ray scattering and fluorescence

    International Nuclear Information System (INIS)

    Kim, S.; Soo, Y.L.; Kioseoglou, G.; Kao, Y.H.; Compaan, A.D.

    2004-01-01

    X-ray reflectivity and angular dependence of x-ray fluorescence (ADXRF) techniques have been employed for a quantitative study of the Te depth profile and structural changes in a series of CdS/CdTe heterojuctions annealed at various temperatures. The temperature dependence of surface roughening and Te migration is observed in both reflectivity and fluorescence experiments. Changes in the interface morphology and Te distribution are quantified by detailed analysis of the ADXRF data with the aid of reflectivity measurements. The results show that a large amount of Te up to 50% could migrate into the CdS layer and suggest that an extra layer of compounds can be formed near the CdS top surface. We have thus demonstrated that the x-ray reflectivity and ADXRF methods can be used as effective tools for nondestructive characterization of the concentration depth profile and interface morphology in layered structures on a nanometer scale

  15. Study of buried junction and uniformity effects in CdTe/CdS solar cells using a combined OBIC and EQE apparatus

    Energy Technology Data Exchange (ETDEWEB)

    Major, J.D. [Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom)], E-mail: j.d.major@durham.ac.uk; Durose, K. [Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom)

    2009-02-02

    A study of junction position and uniformity in CdTe/CdS solar cells is reported in which the influence of excluding oxygen from the CdS layers was investigated. The samples were characterised with an optical beam induced current instrument capable of mapping the cell response in the range 400-900 {mu}m at a resolution of 12.5 {mu}m - either as a map or a quantum efficiency spectrum. For oxygen-free CdS, the junctions were always buried in the CdTe - at a depth presumed to be controlled by the chloride treatment. If CdS:O is used then shallow junctions result, indicating that such layers have a role in doping the devices. The wavelength dependence of the spatial uniformity of the cell's responses is also discussed.

  16. Characterization of Sulfur Bonding in CdS:O Buffer Layers for CdTe-based Thin-Film Solar Cells.

    Science.gov (United States)

    Duncan, Douglas A; Kephart, Jason M; Horsley, Kimberly; Blum, Monika; Mezher, Michelle; Weinhardt, Lothar; Häming, Marc; Wilks, Regan G; Hofmann, Timo; Yang, Wanli; Bär, Marcus; Sampath, Walajabad S; Heske, Clemens

    2015-08-05

    On the basis of a combination of X-ray photoelectron spectroscopy and synchrotron-based X-ray emission spectroscopy, we present a detailed characterization of the chemical structure of CdS:O thin films that can be employed as a substitute for CdS layers in thin-film solar cells. It is possible to analyze the local chemical environment of the probed elements, in particular sulfur, hence allowing insights into the species-specific composition of the films and their surfaces. A detailed quantification of the observed sulfur environments (i.e., sulfide, sulfate, and an intermediate oxide) as a function of oxygen content is presented, allowing a deliberate optimization of CdS:O thin films for their use as alternative buffer layers in thin-film photovoltaic devices.

  17. Mechanical Properties Optimization of Poly-Ether-Ether-Ketone via Fused Deposition Modeling

    Directory of Open Access Journals (Sweden)

    Xiaohu Deng

    2018-01-01

    Full Text Available Compared to the common selective laser sintering (SLS manufacturing method, fused deposition modeling (FDM seems to be an economical and efficient three-dimensional (3D printing method for high temperature polymer materials in medical applications. In this work, a customized FDM system was developed for polyether-ether-ketone (PEEK materials printing. The effects of printing speed, layer thickness, printing temperature and filling ratio on tensile properties were analyzed by the orthogonal test of four factors and three levels. Optimal tensile properties of the PEEK specimens were observed at a printing speed of 60 mm/s, layer thickness of 0.2 mm, temperature of 370 °C and filling ratio of 40%. Furthermore, the impact and bending tests were conducted under optimized conditions and the results demonstrated that the printed PEEK specimens have appropriate mechanical properties.

  18. Alpine Windharvest: development of information base regarding potentials and the necessary technical, legal and socio-economic conditions for expanding wind energy in the Alpine Space - GIS analysis Franches Montagnes, Switzerland - Documentation of GIS concepts, methods and results

    Energy Technology Data Exchange (ETDEWEB)

    Daellenbach, F.; Schaffner, B. [Meteotest, Berne (Switzerland)

    2005-07-01

    This report presents part of the development work carried out by the Swiss meteorology specialists of the company METEOTEST as part of a project carried out together with the Swiss wind-energy organisation 'Suisse Eole'. The framework for the project is the EU Interreg IIIB Alpine Space Programme, a European Community Initiative Programme funded by the European Regional Development Fund. The project investigated the use of digital relief-analysis. The series of reports describes the development and use of a basic information system to aid the investigation of the technical, legal and socio-economical conditions for the use of wind energy in the alpine area. This report documents the use of the Geographic Information Systems (GIS) methodology for the 'Franches Montagnes' Region in Switzerland, whereby the most significant of the model's layers was found to be the wind velocity layer.

  19. Transcriptional analysis of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestial tract model

    DEFF Research Database (Denmark)

    Weiss, Gudrun Margarethe; Jespersen, Lene

    2010-01-01

    The aim of the present study was to investigate the transcription of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestinal tract model. As acidified milk exerted a protective effect on the bacteria leading to increased ...... passage through the gastrointestinal tract; hence, they provide an implementable basis for the selection of prospective probiotic candidates.......The aim of the present study was to investigate the transcription of genes associated with stress and adhesion in Lactobacillus acidophilus NCFM during the passage through an in vitro gastrointestinal tract model. As acidified milk exerted a protective effect on the bacteria leading to increased...... juice, but they were significantly upregulated during incubation in duodenal juice and bile (6- to 7-fold). A significant induction of the gene encoding the S-layer protein was not detected. Our results give a better understanding of the functionality of L. acidophilus NCFM and other probiotics during...

  20. A minimum of three motifs is essential for optimal binding of pseudomurein cell wall-binding domain of Methanothermobacter thermautotrophicus.

    Directory of Open Access Journals (Sweden)

    Ganesh Ram R Visweswaran

    Full Text Available We have biochemically and functionally characterized the pseudomurein cell wall-binding (PMB domain that is present at the C-terminus of the Surface (S-layer protein MTH719 from Methanothermobacter thermautotrophicus. Chemical denaturation of the protein with guanidinium hydrochloride occurred at 3.8 M. A PMB-GFP fusion protein not only binds to intact pseudomurein of methanogenic archaea, but also to spheroplasts of lysozyme-treated bacterial cells. This binding is pH dependent. At least two of the three motifs that are present in the domain are necessary for binding. Limited proteolysis revealed a possible cleavage site in the spacing sequence between motifs 1 and 2 of the PMB domain, indicating that the motif region itself is protected from proteases.

  1. Comparison of CdS films deposited by different techniques: Effects on CdTe solar cell

    International Nuclear Information System (INIS)

    Lee, Jaehyeong

    2005-01-01

    Polycrystalline cadmium sulfide (CdS) thin-films were deposited on glass substrate by chemical bath deposition (CBD) and vacuum evaporation (VE) techniques. VE-CdS films consisted primarily of hexagonal phase, whereas CBD CdS films containing primarily the cubic form. VE-grown films were shown to have better crystallinity than CBD-grown films. The grain size of the CBD films is smaller than the ones of VE films. VE-CdS films exhibited relatively high transmittance in the above-gap region and band gap compared with CBD films. However, CdTe solar cells with these low quality CBD-CdS layers yield higher and more stable characteristics. Current-voltage-temperature measurements showed that the current transport for both cells was controlled by both tunneling and interface recombination but the cells with CBD-CdS displayed less tunneling

  2. High-Performance Elastic Management for Cloud Containers Based on Predictive Message Scheduling

    Directory of Open Access Journals (Sweden)

    Chengxin Yan

    2017-11-01

    Full Text Available Containerized data centers can improve the computational density of IaaS layers. This intensive high-concurrency environment has high requirements for message scheduling and container processing. In the paper, an elastically scalable strategy for cloud containers based on predictive message scheduling is introduced, in order to reduce the delay of messages and improve the response time of services and the utilization of container resources. According to the busy degree of different containers, a management strategy of multiple containers at message-granularity level is developed, which gives the containers better elasticity. The simulation results show that the proposed strategy improves service processing efficiency and reduces response latency compared with existing solutions.

  3. Biosensing for the Environment and Defence: Aqueous Uranyl Detection Using Bacterial Surface Layer Proteins

    Directory of Open Access Journals (Sweden)

    David J.R. Conroy

    2010-05-01

    Full Text Available The fabrication of novel uranyl (UO22+ binding protein based sensors is reported. The new biosensor responds to picomolar levels of aqueous uranyl ions within minutes using Lysinibacillus sphaericus JG-A12 S-layer protein tethered to gold electrodes. In comparison to traditional self assembled monolayer based biosensors the porous bioconjugated layer gave greater stability, longer electrode life span and a denser protein layer. Biosensors responded specifically to UO22+ ions and showed minor interference from Ni2+, Cs+, Cd2+ and Co2+. Chemical modification of JG-A12 protein phosphate and carboxyl groups prevented UO22+ binding, showing that both moieties are involved in the recognition to UO22+.

  4. Security threats and their mitigation in infrastructure as a service

    Directory of Open Access Journals (Sweden)

    Bineet Kumar Joshi

    2016-09-01

    Full Text Available Cloud computing is a hot technology in the market. It permits user to use all IT resources as computing services on the basis of pay per use manner and access the applications remotely. Infrastructure as a service (IaaS is the basic requirement for all delivery models. Infrastructure as a service delivers all possible it resources (Network Components, Operating System, etc. as a service to users. From both users and providers point of view: integrity, privacy and other security issues in IaaS are the important concern. In this paper we studied in detail about the different types of security related issues in IaaS layer and methods to resolve them to maximize the performance and to maintain the highest level of security in IaaS.

  5. Making novel bio-interfaces through bacterial protein recrystallization on biocompatible polylactide derivative films.

    Science.gov (United States)

    Lejardi, Ainhoa; López, Aitziber Eleta; Sarasua, José R; Sleytr, U B; Toca-Herrera, José L

    2013-09-28

    Fabrication of novel bio-supramolecular structures was achieved by recrystallizing the bacterial surface protein SbpA on amorphous and semicrystalline polylactide derivatives. Differential scanning calorimetry showed that the glass transition temperature (T(g)) for (poly-L-lactide)-PLLA, poly(L,D-lactide)-PDLLA, poly(lactide-co-glycolide)-PLGA and poly(lactide-co-caprolactone)-PLCL was 63 °C, 53 °C, 49 °C and 15 °C, respectively. Tensile stress-strain tests indicated that PLLA, PLGA, and PDLLA had a glassy behaviour when tested below T(g). The obtained Young modulus were 1477 MPa, 1330 MPa, 1306 MPa, and 9.55 MPa for PLLA, PLGA, PDLLA, and PLCL, respectively. Atomic force microscopy results confirmed that SbpA recrystallized on every polymer substrate exhibiting the native S-layer P4 lattice (a = b = 13 nm, γ = 90°). However, the polymer substrate influenced the domain size of the S-protein crystal, with the smallest size for PLLA (0.011 μm(2)), followed by PDLLA (0.034 μm(2)), and PLGA (0.039 μm(2)), and the largest size for PLCL (0.09 μm(2)). quartz crystal microbalance with dissipation monitoring (QCM-D) measurements indicated that the adsorbed protein mass per unit area (~1800 ng cm(-2)) was independent of the mechanical, thermal, and crystalline properties of the polymer support. The slowest protein adsorption rate was observed for amorphous PLCL (the polymer with the weakest mechanical properties and lowest T(g)). QCM-D also monitored protein self-assembly in solution and confirmed that S-layer formation takes place in three main steps: adsorption, self-assembly, and crystal reorganization. Finally, this work shows that biodegradable polylactide derivatives films are a suitable support to form robust biomimetic S-protein layers.

  6. A facile approach to fabricate of photothermal functional Fe{sub 3}O{sub 4}@CuS microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Baolong; Shan, Yan, E-mail: shanyan@qust.edu.cn; Chen, Kezheng, E-mail: kchen@qust.edu.cn

    2017-06-01

    Photothermal functional Fe{sub 3}O{sub 4}@CuS microspheres have been prepared successfully by a simple chemical deposition method. The adsorption of cetyltrimethyl-ammonium bromide (CTAB) on the magnetic microspheres plays an important role in forming the structure of the composites. The present materials are characterized with XRD, TEM, SEM, FTIR, and UV-VIS-NIR spectrophotometer. The results show that Fe{sub 3}O{sub 4} microspheres are coated by CuS layer with thickness of 10 nm. The saturation magnetization value of Fe{sub 3}O{sub 4}@CuS core-shell microspheres is 27 emu/g at room temperature and the sample possesses excellent magnetic response in the presence of applied magnetic field. Moreover, these microspheres exhibit good dispersion, suitable size and significant photothermal conversion efficiency up to 20.7% at 808 nm laser irradiation. Fluctuation value of the highest temperature of Fe{sub 3}O{sub 4}@CuS dispersion over four times LASER ON/OFF indicates that photothermal stability of Fe{sub 3}O{sub 4}@CuS microspheres is good. - Highlights: • The Fe{sub 3}O{sub 4} microspheres have been coated with CuS and the thickness of CuS layer is about 10 nm. • The Fe{sub 3}O{sub 4}@CuS microspheres are ferromagnetism, and possess good photothermal conversion efficiency and photostability. • The materials have great potential application for photothermal therapy.

  7. Mechanism of gram variability in select bacteria.

    Science.gov (United States)

    Beveridge, T J

    1990-03-01

    Gram stains were performed on strains of Actinomyces bovis, Actinomyces viscosus, Arthrobacter globiformis, Bacillus brevis, Butyrivibrio fibrisolvens, Clostridium tetani, Clostridium thermosaccharolyticum, Corynebacterium parvum, Mycobacterium phlei, and Propionibacterium acnes, using a modified Gram regimen that allowed the staining process to be observed by electron microscopy (J. A. Davies, G. K. Anderson, T. J. Beveridge, and H. C. Clark, J. Bacteriol. 156:837-845, 1983). Furthermore, since a platinum salt replaced the iodine mordant of the Gram stain, energy-dispersive X-ray spectroscopy could evaluate the stain intensity and location by monitoring the platinum signal. These gram-variable bacteria could be split into two groups on the basis of their staining responses. In the Actinomyces-Arthrobacter-Corynebacterium-Mycobacterium-Propionibacterium group, few cells became gram negative until the exponential growth phase; by mid-exponential phase, 10 to 30% of the cells were gram negative. The cells that became gram negative were a select population of the culture, had initiated septum formation, and were more fragile to the stress of the Gram stain at the division site. As cultures aged to stationary phase, there was a relatively slight increase toward gram negativity (now 15 to 40%) due to the increased lysis of nondividing cells by means of lesions in the side walls; these cells maintained their rod shape but stained gram negative. Those in the Bacillus-Butyrivibrio-Clostridium group also became gram negative as cultures aged but by a separate set of events. These bacteria possessed more complex walls, since they were covered by an S layer. They stained gram positive during lag and the initial exponential growth phases, but as doubling times increased, the wall fabric underlying the S layer became noticeably thinner and diffuse, and the cells became more fragile to the Gram stain. By stationary phase, these cultures were virtually gram negative.

  8. Role of net charge on catalytic domain and influence of cell wall binding domain on bactericidal activity, specificity, and host range of phage lysins.

    Science.gov (United States)

    Low, Lieh Yoon; Yang, Chen; Perego, Marta; Osterman, Andrei; Liddington, Robert

    2011-09-30

    The recombinant lysins of lytic phages, when applied externally to Gram-positive bacteria, can be efficient bactericidal agents, typically retaining high specificity. Their development as novel antibacterial agents offers many potential advantages over conventional antibiotics. Protein engineering could exploit this potential further by generating novel lysins fit for distinct target populations and environments. However, access to the peptidoglycan layer is controlled by a variety of secondary cell wall polymers, chemical modifications, and (in some cases) S-layers and capsules. Classical lysins require a cell wall-binding domain (CBD) that targets the catalytic domain to the peptidoglycan layer via binding to a secondary cell wall polymer component. The cell walls of Gram-positive bacteria generally have a negative charge, and we noticed a correlation between (positive) charge on the catalytic domain and bacteriolytic activity in the absence of the CBD (nonclassical behavior). We investigated a physical basis for this correlation by comparing the structures and activities of pairs of lysins where the lytic activity of one of each pair was CBD-independent. We found that by engineering a reversal of sign of the net charge of the catalytic domain, we could either eliminate or create CBD dependence. We also provide evidence that the S-layer of Bacillus anthracis acts as a molecular sieve that is chiefly size-dependent, favoring catalytic domains over full-length lysins. Our work suggests a number of facile approaches for fine-tuning lysin activity, either to enhance or reduce specificity/host range and/or bactericidal potential, as required.

  9. Relative spike time coding and STDP-based orientation selectivity in the early visual system in natural continuous and saccadic vision: a computational model.

    Science.gov (United States)

    Masquelier, Timothée

    2012-06-01

    We have built a phenomenological spiking model of the cat early visual system comprising the retina, the Lateral Geniculate Nucleus (LGN) and V1's layer 4, and established four main results (1) When exposed to videos that reproduce with high fidelity what a cat experiences under natural conditions, adjacent Retinal Ganglion Cells (RGCs) have spike-time correlations at a short timescale (~30 ms), despite neuronal noise and possible jitter accumulation. (2) In accordance with recent experimental findings, the LGN filters out some noise. It thus increases the spike reliability and temporal precision, the sparsity, and, importantly, further decreases down to ~15 ms adjacent cells' correlation timescale. (3) Downstream simple cells in V1's layer 4, if equipped with Spike Timing-Dependent Plasticity (STDP), may detect these fine-scale cross-correlations, and thus connect principally to ON- and OFF-centre cells with Receptive Fields (RF) aligned in the visual space, and thereby become orientation selective, in accordance with Hubel and Wiesel (Journal of Physiology 160:106-154, 1962) classic model. Up to this point we dealt with continuous vision, and there was no absolute time reference such as a stimulus onset, yet information was encoded and decoded in the relative spike times. (4) We then simulated saccades to a static image and benchmarked relative spike time coding and time-to-first spike coding w.r.t. to saccade landing in the context of orientation representation. In both the retina and the LGN, relative spike times are more precise, less affected by pre-landing history and global contrast than absolute ones, and lead to robust contrast invariant orientation representations in V1.

  10. A pseudaminic acid or a legionaminic acid derivative transferase is strain-specifically implicated in the general protein O-glycosylation system of the periodontal pathogen Tannerella forsythia.

    Science.gov (United States)

    Tomek, Markus B; Janesch, Bettina; Maresch, Daniel; Windwarder, Markus; Altmann, Friedrich; Messner, Paul; Schäffer, Christina

    2017-06-01

    The occurrence of nonulosonic acids in bacteria is wide-spread and linked to pathogenicity. However, the knowledge of cognate nonulosonic acid transferases is scarce. In the periodontopathogen Tannerella forsythia, several proposed virulence factors carry strain-specifically either a pseudaminic or a legionaminic acid derivative as terminal sugar on an otherwise structurally identical, protein-bound oligosaccharide. This study aims to shed light on the transfer of either nonulosonic acid derivative on a proximal N-acetylmannosaminuronic acid residue within the O-glycan structure, exemplified with the bacterium's abundant S-layer glycoproteins. Bioinformatic analyses provided the candidate genes Tanf_01245 (strain ATCC 43037) and TFUB4_00887 (strain UB4), encoding a putative pseudaminic and a legionaminic acid derivative transferase, respectively. These transferases have identical C-termini and contain motifs typical of glycosyltransferases (DXD) and bacterial sialyltransferases (D/E-D/E-G and HP). They share homology to type B glycosyltransferases and TagB, an enzyme catalyzing glycerol transfer to an N-acetylmannosamine residue in teichoic acid biosynthesis. Analysis of a cellular pool of nucleotide-activated sugars confirmed the presence of the CMP-activated nonulosonic acid derivatives, which are most likely serving as substrates for the corresponding transferase. Single gene knock-out mutants targeted at either transferase were analyzed for S-layer O-glycan composition by ESI-MS, confirming the loss of the nonulosonic acid derivative. Cross-complementation of the mutants with the nonnative nonulosonic acid transferase was not successful indicating high stringency of the enzymes. This study identified plausible candidates for a pseudaminic and a legionaminic acid derivative transferase; these may serve as valuable tools for engineering of novel sialoglycoconjugates. © The Author 2017. Published by Oxford University Press.

  11. PbS/CdS-sensitized mesoscopic SnO2 solar cells for enhanced infrared light harnessing.

    Science.gov (United States)

    Hossain, Md Anower; Koh, Zhen Yu; Wang, Qing

    2012-05-28

    Metal oxide semiconductors with lower lying conduction band minimum and superior electron mobility are essential for efficient charge separation and collection in PbS-sensitized solar cells. In the present study, mesoscopic SnO(2) was investigated as an alternative photoanode to the commonly used TiO(2) and examined comprehensively in PbS-sensitized liquid junction solar cells. To exploit the capability of PbS in an optimized structure, cascaded nPbS/nCdS and alternate n(PbS/CdS) layers deposited by a successive ionic layer adsorption and reaction method were systematically scrutinized. It was observed that the surface of SnO(2) has greater affinity to the growth of PbS compared with TiO(2), giving rise to much enhanced light absorption. In addition, the deposition of a CdS buffer layer and a ZnS passivation layer before and after a PbS layer was found to be beneficial for efficient charge separation. Under optimized conditions, cascaded PbS/CdS-sensitized SnO(2) exhibited an unprecedented photocurrent density of 17.38 mA cm(-2) with pronounced infrared light harvesting extending beyond 1100 nm, and a power conversion efficiency of 2.23% under AM 1.5, 1 sun illumination. In comparison, TiO(2) cells fabricated under similar conditions showed much inferior performance owing to the less efficient light harnessing of long wavelength photons. We anticipate that the systematic study of PbS-sensitized solar cells utilizing different metal oxide semiconductors as electron transporters would provide useful insights and promote the development of semiconductor-sensitized mesoscopic solar cells employing panchromatic sensitizers.

  12. Well-resolved oil-soluble Au-doped ZnCdS quantum dots and enhancing doping emission with In-codoping

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Ruosheng, E-mail: zengrsh@gznu.edu.cn [School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004 (China); School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550001 (China); Sun, Zhiguo [School of Chemistry and Materials Science, Guizhou Normal University, Guiyang 550001 (China); Zhou, Chunjiao [College of Science, Hunan Agricultural University, Changsha 410128 (China); Fang, Cheng; Han, Guo-Cheng [School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004 (China); Chen, Zhencheng, E-mail: chenzhcheng@guet.edu.cn [School of Life and Environmental Sciences, Guilin University of Electronic Technology, Guilin 541004 (China)

    2016-06-25

    Highly emissive semiconductor quantum dots (QDs) with tunable color are valuable in many applications such as solid state lighting and bio-imaging. Herein, we report a facile synthetic method to Au:ZnCdS and Au:ZnCdS/ZnS core/shell QDs with tunable emission color. The highly active Au precursor (HAuCl{sub 4}) is prevented to be decomposed at high reaction temperature using 1-dodecanethiol (DDT) as the surface ligand. High-quality Au:ZnCdS/ZnS core/shell QDs are prepared and the highest photoluminescence (PL) quantum yield (QY) can achieve 42% by overcoating of ZnS layer over the bare Au:ZnCdS core QDs. Furthermore, through using Au{sup +} ion as the primary dopants and trivalent cation In{sup 3+} as co-dopants, the PL QY can be enhanced significantly because compensation of In{sup 3+} ion-codoping for the charge imbalance from Au{sup +}-doping. This codoping strategy may be applied to other related optical materials to control the optical properties based on our understanding for physical mechanism. - Highlights: • High-quality oil-soluble Au:ZnCdS/ZnS QDs were prepared for the first time. • The highly active HAuCl4 is prevented to decompose by using 1-dodecanethiol. • The highest PL QY of Au:ZnCdS/ZnS QDs can achieve 42% by overcoating ZnS layer. • The PL QY of QDs can be significantly enhanced by Au{sup +}, In{sup 3+}-codoping.

  13. Vp and Vs velocity models from the Eurasia-Africa plate boundary across the Gloria Fault, North Atlantic Ocean

    Science.gov (United States)

    Batista, Luis; Hübscher, Christian; Terrinha, Pedro; Matias, Luis; Afilhado, Alexandra; Lüdmann, Thomas

    2017-04-01

    The oceanic crustal and uppermost lithospheric mantle structure across the Gloria Fault transcurrent plate boundary between Africa and Eurasia in the Northeast Atlantic is investigated based on seismic reflection, seismic refraction and wide angle reflection data. This experiment used 18 ocean bottom stations along a N-S 150 km long traverse together with coincident acquisition of a multichannel seismic reflection profile. Structural and seismic stratigraphic interpretation of the reflection profile shows that Neogene to recent tectonic deformation on this segment of the plate boundary concentrated on the southern side of the Gloria Fault, i.e. the Africa plate. Modeling of P and S seismic waves and gravimetric anomalies allowed estimation of velocities, density, Poisson's ratio and proposal of a compositional model. A five layer model is proposed in which layers 1 to 3 correspond to normal sediments and typical oceanic crust layers 2 and 3, respectively. Layer 5 yielded mantle velocities above 7.9 km/s. Layer 4 with 4 km of thickness has Vp velocities between 7.1 and 7.4 km/s. Layer 4 velocities can be found at the base of the lower crust and at the uppermost hydrated lithospheric mantle as reported from various authors from other parts of the Earth. Enrichment in olivine at the base of the lower crust, as a result of underplating, could explain Layer 4 velocities; however, there are no morphologic evidences associated to plume activity. On the other hand, morphologic, geologic and seismicity generated along the Gloria Fault (M>7-8.4) indicates that the Gloria Fault has accumulated ductile and brittle deformation from the upper mantle through the surface. It is here argued that pathways for fluid migration through seismic pumping mechanisms have provided the conditions for partial serpentinization of the peridotite mantle rocks, which probably make up the bulk of Layer 4. Publication supported by FCT- project UID/GEO/50019/2013 - Instituto Dom Luiz

  14. Electrical and optical characterization of the influence of chemical bath deposition time and temperature on CdS/Cu(In,Ga)Se2 junction properties in Cu(In,Ga)Se2 solar cells

    International Nuclear Information System (INIS)

    Seo, Han-Kyu; Ok, Eun-A; Kim, Won-Mok; Park, Jong-Keuk; Seong, Tae-Yeon; Lee, Dong Wha; Cho, Hoon Young; Jeong, Jeung-hyun

    2013-01-01

    The effects of varying the conditions for the chemical bath deposition (CBD) of cadmium sulfide (CdS) layers on CdS/Cu(In,Ga)Se 2 (CIGS) hetero-junctions were investigated using photoluminescence (PL), electroluminescence (EL), deep level transient spectroscopy (DLTS), and red-light-illuminated current-voltage (I–V) measurements. We demonstrated that varying CBD-CdS conditions such as the temperature and time influenced the recombination pathways around the CdS/CIGS junction via the formation of different electronic defects, which eventually changed the photovoltaic conversion efficiency. As the CBD-CdS time and temperature were increased, the cell efficiency decreased. PL measurements revealed that this degradation of the cell efficiency was accompanied by increases in the defect-related recombination, which were attributed to the existence of donor defects around CdS/CIGS having an energy level of 0.65 eV below conduction band, as revealed by DLTS. Increasing distortions in the red-light-illuminated I–V characteristics suggested that the related defects might also have played a critical role in metastable changes around the CdS/CIGS junction. Because the CBD-CdS time and temperature were considered to influence the diffusion of impurities into the CIGS surface, the evolution of the efficiency, PL spectra, defect populations, and red-light-illuminated I–V characteristics observed in this work could be attributed to the diffusion of impurities during the CBD-CdS process. - Highlights: • CdS layers were grown by chemical bath deposition (CBD). • The CBD-CdS influenced the efficiency of Cu(In,Ga)Se 2 (CIGS) solar cell. • It could be related to slight alteration in carrier recombination around CdS/CIGS. • Photo- and electroluminescence spectra detected those alterations in recombination. • The variation of results could be related to the changes in deep-level defects

  15. Making novel bio-interfaces through bacterial protein recrystallization on biocompatible polylactide derivative films

    Science.gov (United States)

    Lejardi, Ainhoa; López, Aitziber Eleta; Sarasua, José R.; Sleytr, U. B.; Toca-Herrera, José L.

    2013-09-01

    Fabrication of novel bio-supramolecular structures was achieved by recrystallizing the bacterial surface protein SbpA on amorphous and semicrystalline polylactide derivatives. Differential scanning calorimetry showed that the glass transition temperature (Tg) for (poly-L-lactide)-PLLA, poly(L,D-lactide)-PDLLA, poly(lactide-co-glycolide)-PLGA and poly(lactide-co-caprolactone)-PLCL was 63 °C, 53 °C, 49 °C and 15 °C, respectively. Tensile stress-strain tests indicated that PLLA, PLGA, and PDLLA had a glassy behaviour when tested below Tg. The obtained Young modulus were 1477 MPa, 1330 MPa, 1306 MPa, and 9.55 MPa for PLLA, PLGA, PDLLA, and PLCL, respectively. Atomic force microscopy results confirmed that SbpA recrystallized on every polymer substrate exhibiting the native S-layer P4 lattice (a = b = 13 nm, γ = 90°). However, the polymer substrate influenced the domain size of the S-protein crystal, with the smallest size for PLLA (0.011 μm2), followed by PDLLA (0.034 μm2), and PLGA (0.039 μm2), and the largest size for PLCL (0.09 μm2). quartz crystal microbalance with dissipation monitoring (QCM-D) measurements indicated that the adsorbed protein mass per unit area (˜1800 ng cm-2) was independent of the mechanical, thermal, and crystalline properties of the polymer support. The slowest protein adsorption rate was observed for amorphous PLCL (the polymer with the weakest mechanical properties and lowest Tg). QCM-D also monitored protein self-assembly in solution and confirmed that S-layer formation takes place in three main steps: adsorption, self-assembly, and crystal reorganization. Finally, this work shows that biodegradable polylactide derivatives films are a suitable support to form robust biomimetic S-protein layers.

  16. Josephson junctions with ferromagnetic alloy interlayer

    International Nuclear Information System (INIS)

    Himmel, Nico

    2015-01-01

    Josephson junctions are used as active devices in superconducting electronics and quantum information technology. Outstanding properties are their distinct non-linear electrical characteristics and a usually sinusoidal relation between the current and the superconducting phase difference across the junction. In general the insertion of ferromagnetic material in the barrier of a Josephson junction is associated with a suppression of superconducting correlations. But also new phenomena can arise which may allow new circuit layouts and enhance the performance of applications. This thesis presents a systematic investigation for two concepts to fabricate Josephson junctions with a rather uncommon negative critical current. Such devices exhibit an intrinsic phase slip of π between the electrodes, so they are also known as π junctions. Both studies go well beyond existing experiments and in one system a π junction is shown for the first time. All the thin film junctions are based on superconducting Nb electrodes. In a first approach, barriers made from Si and Fe were investigated with respect to the realisation of π junctions by spin-flip processes. The distribution of Fe in the Si matrix was varied from pure layers to disperse compounds. The systematic fabrication of alloy barriers was facilitated by the development of a novel timing-based combinatorial sputtering technique for planetary deposition systems. An orthogonal gradient approach allowed to create binary layer libraries with independent variations of thickness and composition. Second, Nb vertical stroke AlO x vertical stroke Nb vertical stroke Ni 60 Cu 40 vertical stroke Nb (SIsFS) double barrier junctions were experimentally studied for the occurrence of proximity effect induced order parameter oscillations. Detailed dependencies of the critical current density on the thickness of s-layer and F-layer were acquired and show a remarkable agreement to existing theoretical predictions. Especially a variation of

  17. Results of Experimental and Theoretical Studies of the Atmospheric Turbulence, Internal Gravity Waves and Sporadic-E Layers by Resonant Scattering of Radio Waves on Artificial Periodic Irregularities

    Science.gov (United States)

    Bakhmetieva, Nataliya V.; Grigoriev; Tolmacheva, Ariadna V.

    predominant metallic ions at the E _{s}-layer height is one of the API applications (Bakhmetieva N.V. and Belikovich V.V. Radiophys. Quantum Electron., 2008, Vol. 51, No 11, pp. 956-969). It is based on the observed fact of the local maximum of the API relaxation time at the sporadic E-layer location. The long-lived metallic ions cause the growth of the API relaxation time tauτ at the E _{s}-layer height. It is shown by API technique the sporadic E-layers contain Mg (+) , Ca (+) and Fe (+) ions predominantly at heights of 95-110 km. The new applications are based on the so-called two-frequency method of the API creation and their diagnostics. The method allows one to define the neutral atmosphere and the ionosphere parameters with high accuracy. The main results of the lower ionosphere studies carried out in 2006-2012 by the API technique using the SURA heating facility (56,1 N; 46,15 E) are presented and discussed. We aslo discuss the studies of the HF pumping effects on the formation and parameters of the sporadic E-layers and the modification of the semitransparent E _{s}-layer by the powerful radio wave and diagnostics by the API technique. The work was supported by Russian Foundation for Basic Research under project No 13-02-97067, 13-02-12074 and 13-05-00511.

  18. Josephson junctions with ferromagnetic alloy interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Himmel, Nico

    2015-07-23

    Josephson junctions are used as active devices in superconducting electronics and quantum information technology. Outstanding properties are their distinct non-linear electrical characteristics and a usually sinusoidal relation between the current and the superconducting phase difference across the junction. In general the insertion of ferromagnetic material in the barrier of a Josephson junction is associated with a suppression of superconducting correlations. But also new phenomena can arise which may allow new circuit layouts and enhance the performance of applications. This thesis presents a systematic investigation for two concepts to fabricate Josephson junctions with a rather uncommon negative critical current. Such devices exhibit an intrinsic phase slip of π between the electrodes, so they are also known as π junctions. Both studies go well beyond existing experiments and in one system a π junction is shown for the first time. All the thin film junctions are based on superconducting Nb electrodes. In a first approach, barriers made from Si and Fe were investigated with respect to the realisation of π junctions by spin-flip processes. The distribution of Fe in the Si matrix was varied from pure layers to disperse compounds. The systematic fabrication of alloy barriers was facilitated by the development of a novel timing-based combinatorial sputtering technique for planetary deposition systems. An orthogonal gradient approach allowed to create binary layer libraries with independent variations of thickness and composition. Second, Nb vertical stroke AlO{sub x} vertical stroke Nb vertical stroke Ni{sub 60}Cu{sub 40} vertical stroke Nb (SIsFS) double barrier junctions were experimentally studied for the occurrence of proximity effect induced order parameter oscillations. Detailed dependencies of the critical current density on the thickness of s-layer and F-layer were acquired and show a remarkable agreement to existing theoretical predictions. Especially

  19. Association of fluorescein anterior corneal mosaic and corneal K-structures by in vivo laser confocal microscopy in patients with keratoconus

    Directory of Open Access Journals (Sweden)

    Kobayashi A

    2017-07-01

    Full Text Available Akira Kobayashi, Hideaki Yokogawa, Natsuko Mori, Toshinori Masaki, Kazuhisa Sugiyama Department of Ophthalmology, Graduate School of Medical Science, Kanazawa University, Kanazawa, Japan Objective: To report the in vivo laser confocal microscopy findings of corneas with keratoconus, with special attention to abnormality of Bowman’s layer and sub-Bowman’s fibrous structures (Kobayashi-structures [K-structures].Methods: Sixteen keratoconic eyes in 8 consecutive patients with keratoconus (4 males, 4 females, mean age, 41.1 years were included in this study. Slit-lamp biomicroscopic photos were taken with or without fluorescein staining. The existence of anterior corneal mosaic (ACM after eyelid rubbing under fluorescein staining was documented. In vivo laser confocal microscopic examinations were performed for all patients in both the central cone and the peripheral cornea to examine the existence of K-structures.Results: According to the Amsler–Krumeich scale, the eyes were graded as follows: stage 1 (n=3, stage 2 (n=1, stage 3 (n=1, and stage 4 (n=11. ACM was observed in 7 eyes (61.1% in the cone area and 16 eyes (100% in the peripheral cornea among all keratoconic eyes enrolled in this study. In addition, K-structures were observed in the 7 eyes (61.1% and 16 eyes (100% in the peripheral cornea among all keratoconic eyes. The presence of the K-structures was completely matched (100% with the presence of ACM in both the central cone and the peripheral cornea. In 11 eyes with stage 4 keratoconus, ACM and K-structure was absent in 9 eyes (81.8% in the cone area. On the contrary, in 5 eyes with mild-to-moderate keratoconus (grade 1 to 3, ACM and K-structure was present in all eyes (100% in the cone area. The absent ratio of ACM and K-structures in the cone area was significantly higher in stage 4 severe keratoconus compared to mild-to-moderate keratoconus (grade 1 to 3 (Fisher, P=0.005.Conclusion: The existence of ACM and K

  20. Electrodeposited nickel-cobalt sulfide nanosheet on polyacrylonitrile nanofibers: a binder-free electrode for flexible supercapacitors

    Science.gov (United States)

    Kamran Sami, Syed; Siddiqui, Saqib; Tajmeel Feroze, Muhammad; Chung, Chan-Hwa

    2017-11-01

    To pursue high-performance energy storage devices with both high energy density and power density, one-dimensional (1D) nanostructures play a key role in the development of functional devices including energy conversion, energy storage, and environmental devices. The polyacrylonitrile (PAN) nanofibers were obtained by the versatile electrospinning method. An ultra-thin nickel-cobalt sulfide (NiCoS) layer was conformably electrodeposited on a self-standing PAN nanofibers by cyclic voltammetry to fabricate the light-weighted porous electrodes for supercapacitors. The porous web of PAN nanofibers acts as a high-surface-area scaffold with significant electrochemical performance, while the electrodeposition of metal sulfide nanosheet further enhances the specific capacitance. The fabricated NiCoS on PAN (NiCoS/PAN) nanofibers exhibits a very high capacitance of 1513 F g-1 at 5 A g-1 in 1 M potassium chloride (KCl) aqueous electrolyte with superior rate capability and excellent electrochemical stability as a hybrid electrode. The high capacitance of the NiCoS is attributed to the large surface area of the electrospun PAN nanofibers scaffold, which has offered a large number of active sites for possible redox reaction of ultra-thin NiCoS layer. Benefiting from the compositional features and electrode architectures, the hybrid electrode of NiCoS/PAN nanofibers shows greatly improved electrochemical performance with an ultra-high capacitance (1124 F g-1 at 50 A g-1). Moreover, a binder-free asymmetric supercapacitor device is also fabricated by using NiCoS/PAN nanofibers as the positive electrode and activated carbon (MSP-20) on PAN nanofibers as the negative electrode; this demonstrates high energy density of 56.904 W h kg-1 at a power density of 1.445 kW kg-1, and it still delivers the energy density of 33.3923 W h kg-1 even at higher power density of 16.5013 kW kg-1.

  1. CELULE FOTOVOLTAICE CU HOMOJONCŢIUNE DIN InP: REZULTATE ŞI COMPARĂRI

    Directory of Open Access Journals (Sweden)

    Vasile BOTNARIUC

    2016-12-01

    Full Text Available Au fost obţinute homojoncţiuni n-pInP cu strat intermediar p-InP crescut repetat prin metoda HVPE cu sau fără strat frontal nCdS şi au fost cercetate proprietăţile electrice şi fotoelectrice ale acestora. S-a constatat că depunerea stratului intermediar măreşte fotosensibilitatea homostructurilor cu 15…20%. Eficienţa energetică a CF cu structura n+CdS-n+InP-p-InP-p+InP constituie 13,5% pentru fluxul luminos incident de 100 mW×cm-2. Eficienţa CF cu heterostructura nCdS-pInP şi cu strat intermediar similar creşte cu 27%, în comparaţie cu CF cu homostructura n-p--pInP şi cu strat frontal nCdS, având valoarea de 17,3%. Se conturează posibilitatea reală de mărire a eficienţei CF de acest tip.FOTOVOLTAIC CELLS WITH HOMOJUNCTIONS IN InP: REZULTS AND COMPARISONSElectrical and photoelectrical properties of InP p-n homojunctions with an intermediate p-InP layer repeatedly grown by HVPE method, with and without frontal nCdS layer were produced and studied. It was found that the deposition of this intermediate p-InP layer increases the cells photosensitivity by 15 ... 20%. The solar energy conversion efficiency of photovoltaic cell (PC with n+CdS-n+InP-p-InP-p+InP structure is 13.5% at the illumination of 100 mW.cm-2. The efficiency of the PC based on nCdS-pInP heterostructure and an analogic intermediate layer increases to 27% compared with the PC based on n-p--pInP homostructure having a frontal nCdS layer has an efficiency of 17.3%. The possibility of increasing of the efficiency of this PC type is formulated.

  2. Grain size distribution, clay mineralogy and chemistry of bottom sediments from the outer Thermaikos Gulf, Aegean Sea, Greece

    Directory of Open Access Journals (Sweden)

    K.G. PEHLIVANOGLOU

    2004-06-01

    Full Text Available The Thermaikos Gulf constitutes the NW part of the North Aegean Sea and is limited eastward from the Chalkidiki Peninsula and westward from the Pieria Prefecture. Its plateau covers an area of 3,500 km2. The mechanisms responsible for the grain size distribution into the Gulf, the clay mineralogy and the chemistry of some bottom sediments from the outer Thermaikos Gulf, are examined. Source mixing during transportation, flocculation, differential settling processes and organic matter appear to be the main mechanisms for the distribution of clay minerals in shallow waters. All grain size fractions studied present a wide range of values confirming the extreme variations of the discharged load and the variability in marine processes. Plagioclases predominate over K-feldspars, while quartz is the most abundant mineral present. In addition, micas, chlorites, amphiboles and pyroxenes exist as primary and/or accessory minerals in all samples. Among clay minerals, illite predominates over smectite and smectite over chlorite (+ kaolinite. The ordered interstratified phase of I/S, with 30-35% S layers, is present in the 2-0.25µm fraction. The randomly interstratified phase of I/S, with 50% S layers, is present in the <0.25& micro; m fraction. On average the clay mineral content of the studied samples is: 48% I, 23% S, 17% Ch (+K and 12% others for the 2-0.25µm fraction and 50% I, 30% S and 20% Ch (+K for the <0.25 µm fraction. All these minerals are the weathering products of the rocks from the drainage basins of the rivers flowing into the Gulf, as well as of the Neogene and Quaternary unconsolidated sediments of the surrounding coasts. The terrigenous input, the water mass circulation and, to a lesser extent, the quality of the discharged material and the differential settling of grains, control the grain size distribution within the outer Thermaikos Gulf. The chemical composition of the analysed samples is generally in agreement with their mineral

  3. Advanced electron microscopy of wide band-gap semiconductor materials

    International Nuclear Information System (INIS)

    Fay, M.W.

    2000-10-01

    The microstructure of GaN layers grown by metal organic vapour phase epitaxy on (0001) sapphire substrates using a novel precursor for deposition of AlN buffer layers has been investigated and compared to layers grown using low temperature GaN buffer layers and state-of-the-art material. It has been shown that the quality of layers grown using the novel precursor is comparable to the state-of-the-art material. TEM analysis has been performed of multiple quantum wells of InGaN grown within GaN epitaxial layers by metal organic vapour phase epitaxy. Elementally sensitive TEM techniques have been used to determine the spatial distribution of In and Ga within these structures. Fluctuations in In sensitive images are observed on the nm-scale. Clear evidence of segregation of In during layer growth has been seen. Models of the In segregation are in good agreement with experimental results. Elementally sensitive techniques have been used to investigate the elemental distributions in TiAl and NiAu contacts to GaN. Annealing of TiAl contacts has been seen to result in the formation of a thin interfacial Ti rich phase, and of N depletion at the surface of the GaN layer to the depth of tens of nm. Annealing NiAu contacts at 700 deg. C was seen to result in the formation of Ga-rich interfacial phases, of both crystalline and amorphous structure. ZnS and ZnCdS layers grown on (001) GaP supplied by the University of Hull have been investigated. ZnS layers were found to contain a high density of inclined stacking faults throughout the layer, originating from the interface with the substrate. Energy sensitive techniques have been used to investigate ZnCdS quantum well structures. The use of a ZnCdS superlattice structure around a ZnCdS quantum well to approximate a reduced barrier was seen to result in less thickness variations than when no barrier was used. (author)

  4. Enhanced Performance of Nanoporous Titanium Dioxide Solar Cells Using Cadmium Sulfide and Poly(3-hexylthiophene Co-Sensitizers

    Directory of Open Access Journals (Sweden)

    Murugathas Thanihaichelvan

    2017-09-01

    Full Text Available This work reports the effect of co-sensitization of nanoporous titanium dioxide using Cadmium Sulfide (CdS and poly(3-hexylthiophene (P3HT on the performance of hybrid solar cells. CdS nanolayer with different thicknesses was grown on Titanium Dioxide (TiO2 nanoparticles by chemical bath deposition technique with varying deposition times. Both atomic force microscopy (AFM and UV–Vis–NIR spectroscopy measurements of TiO2 electrode sensitized with and without CdS layer confirm that the existence of CdS layer on TiO2 nanoparticles. AFM images of CdS-coated TiO2 nanoparticles show that the surface roughness of the TiO2 nanoparticle samples decreases with increasing CdS deposition times. Current density–voltage and external quantum efficiency (EQE measurements were carried out for corresponding solar cells. Both short circuit current density (JSC and fill factor were optimized at the CdS deposition time of 12 min. On the other hand, a steady and continuous increment in the open circuit voltage (VOC was observed with increasing CdS deposition time and increased up to 0.81 V when the deposition time was 24 min. This may be attributed to the increased gradual separation of P3HT and TiO2 phases and their isolation at the interfaces. The higher VOC of 0.81 V was due to the higher built-in voltage at the CdS–P3HT interface when compared to that at the TiO2–P3HT interface. Optimized nanoporous TiO2 solar cells with CdS and P3HT co-sensitizers showed external quantum efficiency (EQE of over 40% and 80% at the wavelengths corresponding to strong absorption of the polymer and CdS, respectively. The cells showed an overall average efficiency of over 2.4% under the illumination of 70 mW/cm2 at AM 1.5 condition.

  5. Retardation of iron-cyanide complexes in the soil of a former manufactured gas plant site.

    Science.gov (United States)

    Sut, Magdalena; Repmann, Frank; Raab, Thomas

    2015-01-01

    The soil in the vicinities of former Manufactured Gas Plant (MGP) sites is commonly contaminated with iron-cyanide complexes (ferric ferrocyanide). The phenomenon of cyanide mobility in soil, according to the literature, is mainly governed by the dissolution and precipitation of ferric ferrocyanide, which is only slightly soluble (soil and the potential vertical movement of the solid iron-cyanide complexes, co-existing with the dissolution, sorption and precipitation reactions were investigated. Preliminary research conducted on a former MGP site implied colloidal transport of ferric ferricyanide from the initial deposition in the wastes layer towards the sandy loam material (secondary accumulation), which possibly retarded the mobility of cyanide (CN). A series of batch and column experiments were applied in order to investigate the retardation of iron-cyanide complexes by the sandy loam soil. Batch experiments revealed that in circumneutral pH conditions sandy loam material decreases the potassium ferro- and ferricyanide concentration. In column experiments a minor reduction in CN concentration was observed prior to addition of iron sulfide (FeS) layer, which induced the formation of the Prussian blue colloids in circumneutral pH conditions. Precipitated solid iron-cyanide complexes were mechanically filtered by the coherent structure of the investigated soil. Additionally, the reduction of the CN concentration of the percolation solutions by the sandy loam soil was presumably induced due to the formation of potassium manganese iron-cyanide (K2Mn[Fe(CN)6]).

  6. Optimization of SnS active layer thickness for solar cell application

    Science.gov (United States)

    Gupta, Yashika; Arun, P.

    2017-11-01

    This work presents a comparative study of n-SnS and p-SnS active layers for increased solar cell efficiency. Tin sulphide thin films of various thicknesses having p-type and n-type conductivity were fabricated by thermal evaporation. Both type of films had the same (113) orientation of the crystal planes with a constant tensile strain of ~ 0.003 and ~ 0.011, respectively. The persistent photocurrent was observed in all n-SnS and p-SnS samples with the current’s time decay constant decreasing with increasing film thickness. Hole mobility of thicker p-SnS films was found to be greater than the electron mobility in n-SnS samples, with mobility (both hole and electron) showing an increasing trend with film thickness. The optimum absorber layer thickness for both p- and n-SnS layers should have a high value of diffusion length for a given absorption coefficient and band-gap.

  7. Trends in development of surface modification technologies; Hyomen kaishitsu gijutsu no kaihatsu no genjo

    Energy Technology Data Exchange (ETDEWEB)

    Nakata, K. [Osaka University, Osaka (Japan). Joining and Welding Research Institute

    1998-06-01

    The latest technologies involving thin-film coating and diffusion are outlined. The Ti-base ceramic film coating is quite hard, and contributes to the prolongation of the service life of cutting tools, punches, metal molds, etc. Among the coating techniques, there are thermal CVD (chemical vapor deposition), ion plating, sputtering, etc. As for coating materials, TiN, TiCN, and TiAlN are well known. Methods for improving the adhesion between a substrate and coating are quite important. Coatings made of diamond, c-BN, and {beta}-C3N4 may be mentioned as next-generation abrasion-proof ultra-hard coatings. There are very lubricating coatings which are high in hardness but low in friction factor and therefore are suitable for application as a slide member that do not wear the other member. They are represented by coatings composed of CrN, diamond-like carbon, and WC/C. There are the radical nitriding method, in which NH3 and H2 act as reaction gases in a low voltage glow discharge for the generation of NH radicals for the formation of a nitride layer, and the nitrosulphurizing method, in which an FeS layer and a nitride layer thereunder are formed by use of H2S+N2+NH3(+CO2) gas, these two methods belonging to the diffusion technique that is a topic often discussed these days. 24 refs., 7 figs., 2 tabs.

  8. Production method of thin film solar cell; Hakumaku taiyo denchi no seizo hoho

    Energy Technology Data Exchange (ETDEWEB)

    Oki, K.; Watanabe, T.; Matsui, M.

    1996-01-23

    This invention relates to the film formation of chalcopyrite type compound semiconductor used for thin film solar cell. In the case of CuInS2 thin film, heteromorphic phases such as CuIn5S8, Cu2S, and In2S3 are formed on the top surface together with the CuInS2 phase, resulting in the decrease in junction property when n-type semiconductor layer such as CdS layer is formed on it. According to the invention, p-type semiconductor layer made of chalcopyrite type compound semiconductor is dipped into an ammonia water before being laminated with n-type semiconductor layer. Although higher concentration and higher temperature of the ammonia water accelerates the heteromorphic phase film removal velocity, it also gives rise to higher evaporation rate of ammonia. The preferable concentration and temperature are, therefore, 0.01 - 50% and 5 - 80{degree}C, respectively. In this way, the chalcopyrite type compound semiconductor thin film free from heteromorphic phases on its surface can be produced. The thin film solar cell produced by using such thin film has a high conversion efficiency because of a good junction property with n-type semiconductor. 1 fig.

  9. Pt/In2S3/CdS/Cu2ZnSnS4 Thin Film as an Efficient and Stable Photocathode for Water Reduction under Sunlight Radiation.

    Science.gov (United States)

    Jiang, Feng; Gunawan; Harada, Takashi; Kuang, Yongbo; Minegishi, Tsutomu; Domen, Kazunari; Ikeda, Shigeru

    2015-10-28

    An electrodeposited Cu2ZnSnS4 (CZTS) compact thin film modified with an In2S3/CdS double layer and Pt deposits (Pt/In2S3/CdS/CZTS) was used as a photocathode for water splitting of hydrogen production under simulated sunlight (AM 1.5G) radiation. Compared to platinized electrodes based on a bare CZTS film (Pt/CZTS) and a CZTS film modified with a CdS single layer (Pt/CdS/CZTS), the Pt/In2S3/CdS/CZTS electrode exhibited a significantly high cathodic photocurrent. Moreover, the coverage of the In2S3 layer was found to be effective for stabilization against degradation induced by photocorrosion of the CdS layer. Bias-free water splitting with a power conversion efficiency of 0.28% was achieved by using a simple two-electrode cell consisting of the Pt/In2S3/CdS/CZTS photocathode and a BiVO4 photoanode.

  10. A facile in situ synthesis route for CuInS(2) quantum-dots/In(2)S(3) co-sensitized photoanodes with high photoelectric performance.

    Science.gov (United States)

    Wang, Yuan-Qiang; Rui, Yi-Chuan; Zhang, Qing-Hong; Li, Yao-Gang; Wang, Hong-Zhi

    2013-11-27

    CuInS2 quantum-dot sensitized TiO2 photoanodes with In2S3 buffer layer were in situ prepared via chemical bath deposition of In2S3, where the Cd-free In2S3 layer then reacted with TiO2/CuxS which employed a facile SILAR process to deposit CuxS quantum dots on TiO2 film, followed by a covering process with ZnS layer. Polysulfide electrolyte and Cu2S on FTO glass counter electrode were used to provide higher photovoltaic performance of the constructed devices. The characteristics of the quantum dots sensitized solar cells were studied in more detail by optical measurements, photocurrent-voltage performance measurements, and impedance spectroscopy. On the basis of optimal CuxS SILAR cycles, the best photovoltaic performance with power conversion efficiency (η) of 1.62% (Jsc = 6.49 mA cm(-2), Voc = 0.50 V, FF = 0.50) under full one-sun illumination was achieved by using Cu2S counter electrode. Cu2S-FTO electrode exhibits superior electrocatalytic ability for the polysulfide redox reactions relative to that of Pt-FTO electrode.

  11. Surface modifications of chalcopyrite CuInS2 thin films for photochatodes in photoelectrochemical water splitting under sunlight irradiation

    Science.gov (United States)

    Gunawan; Haris, A.; Widiyandari, H.; Septina, W.; Ikeda, S.

    2017-02-01

    Copper chalcopyrite semiconductors include a wide range of compounds that are of interest for photoelectrochemical water splitting which enables them to be used as photochatodes for H2 generation. Among them, CuInS2 is one of the most important materials due to its optimum band gap energy for sunlight absorption. In the present study, we investigated the application of CuInS2 fabricated by electrodeposition as photochatodes for water splitting. Thin film of CuInS2 chalcopyrite was formed on Mo-coated glass substrate by stacked electrodeposition of copper and indium followed by sulfurization under H2S flow. The films worked as a H2 liberation electrode under cathodic polarization from a solution containing Na2SO4 after loading Pt deposits on the film. Introduction of an n-type CdS layer by chemical bath deposition on the CuInS2 surface before the Pt loading resulted appreciable improvements of H2 liberation efficiency and a higher photocurrent onset potential. Moreover, the use of In2S3 layer as an alternative n-type layer to the CdS significantly improved the H2 liberation performance: the CuInS2 film modified with In2S3 and Pt deposits worked as an efficient photocathode for photoelectrochemical water splitting.

  12. Investigation of the Electric Structures of Heterointerfaces in Pt- and In₂S₃-Modified CuInS₂ Photocathodes Used for Sunlight-Induced Hydrogen Evolution.

    Science.gov (United States)

    Gunawan; Septina, Wilman; Harada, Takashi; Nose, Yoshitaro; Ikeda, Shigeru

    2015-07-29

    Copper indium disulfide (CuInS2) modified with an In2S3 layer and a Pt catalyst showed a more efficient photoelectrochemical (PEC) property for hydrogen evolution from a nearly neutral (pH 6) 0.2 M NaH2PO4 solution under simulated sunlight illumination (AM 1.5G) than that of a CuInS2 electrode modified with a CdS layer and a Pt catalyst. Analysis of the PEC properties of In2S3-modified CuInS2 (In2S3/CuInS2) and CdS-modified CuInS2 (CdS/CuInS2) in solutions containing an electron scavenger (Eu(3+)) showed identical enhancement of the PEC properties of In2S3/CuInS2 when compared to those of CdS/CuInS2, indicating the formation of a favorable heterointerface in In2S3/CuInS2 for efficient charge separation. Spectroscopic evaluation of conduction band offsets revealed that In2S3/CuInS2 had a notch-type conduction band offset, whereas a cliff-type offset was formed in CdS/CuInS2: these results also revealed a better interface electric structure of In2S3/CuInS2 than that of CdS/CuInS2.

  13. Complex Boron Redistribution in P+ Doped-polysilicon / Nitrogen Doped Silicon Bi-layers during Activation Annealing

    Science.gov (United States)

    Abadli, S.; Mansour, F.; Perrera, E. Bedel

    We have investigated and modeled the complex phenomenon of boron (B) redistribution process in strongly doped silicon bilayers structure. A one-dimensional two stream transfer model well adapted to the particular structure of bi- layers and to the effects of strong-concentrations has been developed. This model takes into account the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method, using in-situ nitrogen- doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P+) layer. To avoid long redistributions, thermal annealing was carried out at relatively lowtemperatures (600 °C and 700 °C) for various times ranging between 30 minutes and 2 hours. The good adjustment of the simulated profiles with the experimental secondary ion mass spectroscopy (SIMS) profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders kinetics.

  14. Complex boron redistribution kinetics in strongly doped polycrystalline-silicon/nitrogen-doped-silicon thin bi-layers

    Energy Technology Data Exchange (ETDEWEB)

    Abadli, S. [Department of Electrical Engineering, University Aout 1955, Skikda, 21000 (Algeria); LEMEAMED, Department of Electronics, University Mentouri, Constantine, 25000 (Algeria); Mansour, F. [LEMEAMED, Department of Electronics, University Mentouri, Constantine, 25000 (Algeria); Pereira, E. Bedel [CNRS-LAAS, 7 avenue du colonel Roche, 31077 Toulouse (France)

    2012-10-15

    We have investigated the complex behaviour of boron (B) redistribution process via silicon thin bi-layers interface. It concerns the instantaneous kinetics of B transfer, trapping, clustering and segregation during the thermal B activation annealing. The used silicon bi-layers have been obtained by low pressure chemical vapor deposition (LPCVD) method at 480 C, by using in-situ nitrogen-doped-silicon (NiDoS) layer and strongly B doped polycrystalline-silicon (P{sup +}) layer. To avoid long-range B redistributions, thermal annealing was carried out at relatively low-temperatures (600 C and 700 C) for various times ranging between 30 min and 2 h. To investigate the experimental secondary ion mass spectroscopy (SIMS) doping profiles, a redistribution model well adapted to the particular structure of two thin layers and to the effects of strong-concentrations has been established. The good adjustment of the simulated profiles with the experimental SIMS profiles allowed a fundamental understanding about the instantaneous physical phenomena giving and disturbing the complex B redistribution profiles-shoulders. The increasing kinetics of the B peak concentration near the bi-layers interface is well reproduced by the established model. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Formation of a ZnS/Zn(S,O) bilayer buffer on CuInS2 thin film solar cell absorbers by chemical bath deposition

    Science.gov (United States)

    Bär, M.; Ennaoui, A.; Klaer, J.; Kropp, T.; Sáez-Araoz, R.; Allsop, N.; Lauermann, I.; Schock, H.-W.; Lux-Steiner, M. C.

    2006-06-01

    The application of Zn compounds as buffer layers was recently extended to wide-gap CuInS2 (CIS) based thin film solar cells. Using an alternative chemical deposition route for the buffer preparation aiming at the deposition of a single-layer, nominal ZnS buffer without the need for any toxic reactants such as hydrazine has helped us to achieve a similar efficiency as respective CdS-buffered reference devices. In order to shed light on the differences of other Zn-compound buffers deposited in conventional chemical baths [chemical bath deposition (CBD)] compared to the buffer layers deposited by this alternative CBD process, the composition of the deposited buffers was investigated by x-ray excited Auger electron and x-ray photoelectron spectroscopy to potentially clarify their superiority in terms of device performance. We have found that in the early stages of this alternative CBD process a thin ZnS layer is formed on the CIS, whereas in the second half of the CBD the growth rate is greatly increased and Zn(S,O) with a ZnS/(ZnS+ZnO) ratio of ~80% is deposited. Thus, a ZnS/Zn(S,O) bilayer buffer is deposited on the CIS thin film solar cell absorbers by the alternative chemical deposition route used in this investigation. No major changes of these findings after a postannealing of the buffer/CIS sample series and recharacterization could be identified.

  16. Analytical Modeling for the Bending Resonant Frequency of Multilayered Microresonators with Variable Cross-Section

    Directory of Open Access Journals (Sweden)

    Jian Lu

    2011-08-01

    Full Text Available Multilayered microresonators commonly use sensitive coating or piezoelectric layers for detection of mass and gas. Most of these microresonators have a variable cross-section that complicates the prediction of their fundamental resonant frequency (generally of the bending mode through conventional analytical models. In this paper, we present an analytical model to estimate the first resonant frequency and deflection curve of single-clamped multilayered microresonators with variable cross-section. The analytical model is obtained using the Rayleigh and Macaulay methods, as well as the Euler-Bernoulli beam theory. Our model is applied to two multilayered microresonators with piezoelectric excitation reported in the literature. Both microresonators are composed by layers of seven different materials. The results of our analytical model agree very well with those obtained from finite element models (FEMs and experimental data. Our analytical model can be used to determine the suitable dimensions of the microresonator’s layers in order to obtain a microresonator that operates at a resonant frequency necessary for a particular application.

  17. Profile of Secreted Hydrolases, Associated Proteins, and SlpA in Thermoanaerobacterium saccharolyticum during the Degradation of Hemicellulose

    Energy Technology Data Exchange (ETDEWEB)

    Currie, Devin [Dartmouth College; Guss, Adam M [ORNL; Herring, Christopher [Mascoma Corporation; Giannone, Richard J [ORNL; Johnson, Courtney M [ORNL; Lankford, Patricia K [ORNL; Brown, Steven D [ORNL; Hettich, Robert {Bob} L [ORNL; Lynd, Lee R [Thayer School of Engineering at Dartmouth

    2014-01-01

    Thermoanaerobacterium saccharolyticum, a Gram-positive thermophilic anaerobic bacterium, grows robustly on insoluble hemicellulose, which requires a specialized suite of secreted and transmembrane proteins. We report here the characterization of proteins secreted by this organism. Cultures were grown on hemicellulose, glucose, xylose, starch, and xylan in pH-controlled bioreactors, and samples were analyzed via spotted microarrays and liquid chromatography-mass spectrometry. Key hydrolases and transporters employed by T. saccharolyticum for growth on hemicellulose were, for the most part, hitherto uncharacterized and existed in two clusters (Tsac_1445 through Tsac_1464 for xylan/xylose and Tsac_1344 through Tsac_1349 for starch). A phosphotransferase system subunit, Tsac_0032, also appeared to be exclusive to growth on glucose. Previously identified hydrolases that showed strong conditional expression changes included XynA (Tsac_1459), XynC (Tsac_0897), and a pullulanase, Apu (Tsac_1342). An omnipresent transcript and protein making up a large percentage of the overall secretome, Tsac_0361, was tentatively identified as the primary S-layer component in T. saccharolyticum, and deletion of the Tsac_0361 gene resulted in gross morphological changes to the cells. The view of hemicellulose degradation revealed here will be enabling for metabolic engineering efforts in biofuel-producing organisms that degrade cellulose well but lack the ability to catabolize C5 sugars

  18. Synthesis and optical characterization of single phased ZnS:Mn²⁺/CdS core-shell nanoparticles.

    Science.gov (United States)

    Murugadoss, G; Ramasamy, V

    2012-07-01

    Uncoated ZnS, ZnS:Mn(2+), CdS and different thickness of CdS coated ZnS:Mn(2+) core-shell nanoparticles were successfully synthesized by a simple chemical method in an air atmosphere. X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques were used to characterize the uncoated and the novel ZnS:Mn(2+)/CdS core-shell nanoparticles. The results show that the size of the ZnS:Mn(2+)/CdS core-shell nanoparticles is less than the bare ZnS:Mn(2+). The PL study of ZnS:Mn(2+)/CdS core-shell nanoparticles shows an enhanced intensity than ZnS:Mn(2+). The coating of CdS layer over ZnS:Mn(2+) tuned the PL emission in the visible region. Addition of cadmium acetate (Cd 4 and 5M) in ZnS:Mn(2+) shows a distinct PL peak centered at 542 nm. The presence of Mn(2+) ions in ZnS lattice and the growth of the CdS on ZnS:Mn(2+) nanoparticles were confirmed by the ESR spectra. Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Preparation and Characterization of Coevaporated Cd1−xZnxS Alloy Thin Films

    Directory of Open Access Journals (Sweden)

    Wei Li

    2011-01-01

    Full Text Available Cd1-xZnxS thin films have been prepared by the vacuum coevaporation method. The structural, compositional, and optical properties of Cd1-xZnxS thin films have been investigated using X-ray diffraction, X-ray fluorescence, and optical transmittance spectra. As-deposited Cd1-xZnxS thin films are polycrystalline and show the cubic structure for x=1 and hexagonal one for x<1 with the highly preferential orientation. The composition of Cd1-xZnxS thin films determined from Vegard's law and quartz thickness monitors agrees with that determined from the X-ray fluorescence spectra. Optical absorption edge of optical transmittance for Cd1-xZnxS thin films shows a blue shift with the increase of the zinc content. The band gap for Cd1-xZnxS thin films can be tuned nonlinearly with x from about 2.38 eV for CdS to 3.74 eV for ZnS. A novel structure for CuInS2-based solar cells with a Cd0.4Zn0.6S layer is proposed in this paper.

  20. pi-phase magnetism in ferromagnetic-superconductor superlattices

    CERN Document Server

    Khusainov, M G; Proshin, Y N

    2001-01-01

    The Larkin-Ovchinnikov-Fylde-Ferrel new 0 pi- and pi pi-states are forecasted for the ferromagnetic metal/superconductor superlattices with antiferromagnetic magnetization orientation in the neighbouring layers. The above-mentioned states are characterized under certain conditions by higher critical temperature T sub c as compared to the earlier known LOFF 00- and pi 0-states with the FM-layers ferromagnetic ordering. It is shown that the nonmonotonous behavior of the T sub c of the FM/S superlattices by the thickness of the S-layers lower than the d sub s suppi value is connected with the cascades of the 0 pi-pi pi-0 pi phase transitions. The character of the T sub c oscillations by the d sub s > d sub s suppi is related to the 00-pi 0-00 transitions. The logical elements of the new type, combining the advantages of the superconducting and magnetic information recording in one sample are proposed on the basis of the FM/S superlattices

  1. Synthesis of Copper-Antimony-Sulfide Nanocrystals for Solution-Processed Solar Cells.

    Science.gov (United States)

    Suehiro, Satoshi; Horita, Keisuke; Yuasa, Masayoshi; Tanaka, Tooru; Fujita, Katsuhiko; Ishiwata, Yoichi; Shimanoe, Kengo; Kida, Tetsuya

    2015-08-17

    The p-type nanocrystals (NCs) of copper-based chalcogenides, such as CuInSe2 and Cu2ZnSnS4, have attracted increasing attention in photovoltaic applications due to their potential to produce cheap solution-processed solar cells. Herein, we report the synthesis of copper-antimony-sulfide (CAS) NCs with different crystal phases including CuSbS2, Cu3SbS4, and Cu12Sb4S13. In addition, their morphology, crystal phase, and optical properties were characterized using transmission electron microscopy, X-ray diffractometry, UV-vis-near-IR spectroscopy, and photoemission yield spectroscopy. The morphology, crystal phase, and electronic structure were significantly dependent on the chemical composition in the CAS system. Devices were fabricated using particulate films consisting of CAS NCs prepared by spin coating without a high-temperature treatment. The CAS NC-based devices exhibited a diode-like current-voltage characteristic when coupled with an n-type CdS layer. In particular, the CuSbS2 NC devices exhibited photovoltaic responses under simulated sunlight, demonstrating its applicability for use in solution-processed solar cells.

  2. Dynamic analysis of the photoenhancement process of colloidal quantum dots with different surface modifications

    Energy Technology Data Exchange (ETDEWEB)

    Valledor Llopis, Marta; Campo Rodriguez, Juan Carlos; Ferrero Martin, Francisco J [Departamento de Ingenieria Electrica, Electronica, C y S Universidad de Oviedo, Campus de Gijon s/n, 33204 Gijon, Asturias, (Spain); Coto, Ana Maria; Fernandez-Argueelles, Maria T; Costa-Fernandez, J M; Sanz-Medel, A [Departamento de Quimica Fisica y Analitica, Universidad de Oviedo, Campus del Cristo, 33006 Oviedo, Asturias (Spain)

    2011-09-23

    Photoinduced fluorescence enhancement of colloidal quantum dots (QDs) is a hot topic addressed in many studies due to its great influence on the bioanalytical performance of such nanoparticles. However, understanding of this process is not a simple task, and it cannot be explained by a general mechanism as it greatly depends on the QDs' nature, solubilization strategies, surrounding environment, etc. In this vein, we have critically compared the behavior of CdSe QDs (widely used in bioanalytical applications) with different surface modifications (ligand exchange and polymer coating), in different controlled experimental conditions, in the presence-absence of the ZnS layer and in different media when exposed for long times to intense UV irradiation. Thus six different types of colloidal QDs were finally studied. This research was carried out from a novel perspective, based on the analysis of the dynamic behavior of the photoactivation process (of great interest for further applications of QDs as labels in biomedical applications). The results showed a different behavior of the studied colloidal QDs after UV irradiation in terms of their photoluminescence characteristics, potential toxicity due to metal release to the environment, nanoparticle stability and surface coating degradation.

  3. Methanoculleus palmolei sp. nov., an irregularly coccoid methanogen from an anaerobic digester treating wastewater of a palm oil plant in north-Sumatra, Indonesia.

    Science.gov (United States)

    Zellner, G; Messner, P; Winter, J; Stackebrandt, E

    1998-10-01

    Strain INSLUZT (= DSM 4273T) was isolated from a biogas-producing bioreactor treating wastewater of a palm oil mill on North-Sumatra (Indonesia). Cells of strain INSLUZT were highly irregularly coccoid, 1.25-2.0 microns in diameter, had a cell envelope consisting of the cytoplasmic membrane and an S-layer of hexagonally arranged glycoprotein subunits with an M(r) of 120,000, and were flagellated (motility was not observed). Cells were mesophilic and grew most rapidly at 40 degrees C on H2/CO2' formate, 2-propanol/CO2 2-butanol/CO2 and cyclopentanol/CO2 to give methane. Tungstate promoted growth on H2/CO2 with acetate as the solely required organic medium supplement. The G + C content of DNA was 59 mol% (Tm method) and 59.5 mol% (HPLC method). 16S rDNA analysis revealed a phylogenetic relationship to Methanoculleus species; the name Methanoculleus palmolei sp. nov. is therefore proposed for strain INSLUZT (= DSM 4273T).

  4. Construction of a high-efficiency cloning system using the Golden Gate method and I-SceI endonuclease for targeted gene replacement in Bacillus anthracis.

    Science.gov (United States)

    Wang, Tiantian; Wang, Dongshu; Lyu, Yufei; Feng, Erling; Zhu, Li; Liu, Chunjie; Wang, Yanchun; Liu, Xiankai; Wang, Hengliang

    2018-02-10

    To investigate gene function in Bacillus anthracis, a high-efficiency cloning system is required with an increased rate of allelic exchange. Golden Gate cloning is a molecular cloning strategy allowing researchers to simultaneously and directionally assemble multiple DNA fragments to construct target plasmids using type IIs restriction enzymes and T4 DNA ligase in the same reaction system. Here, a B. anthracis S-layer protein EA1 allelic exchange vector was successfully constructed using the Golden Gate method. No new restriction sites were introduced into this knockout vector, and seamless assembly of the DNA fragments was achieved. To elevate the efficiency of homologous recombination between the allelic exchange vector and chromosomal DNA, we introduced an I-SceI site into the allelic exchange vector. The eag gene was successfully knocked out in B. anthracis using this vector. Simultaneously, the allelic exchange vector construction method was developed into a system for generating B. anthracis allelic exchange vectors. To verify the effectiveness of this system, some other allelic exchange vectors were constructed and gene replacements were performed in B. anthracis. It is speculated that this gene knockout vector construction system and high-efficiency targeted gene replacement using I-SceI endonuclease can be applied to other Bacillus spp. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  5. Molecular biomineralization: toward an understanding of the biogenic origin of polymetallic nodules, seamount crusts, and hydrothermal vents.

    Science.gov (United States)

    Wang, Xiaohong; Wiens, Matthias; Schröder, Heinz C; Schloßmacher, Ute; Müller, Werner E G

    2011-01-01

    Polymetallic nodules and crusts, hydrothermal vents from the Deep Sea are economically interesting, since they contain alloying components, e.g., manganese or cobalt, that are used in the production of special steels; in addition, they contain rare metals applied for plasma screens, for magnets in hard disks, or in hybrid car motors. While hydrothermal vents can regenerate in weeks, polymetallic nodules and seamount crusts grow slowly. Even though the geochemical basis for the growth of the nodules and crusts has been well studied, the contribution of microorganisms to the formation of these minerals remained obscure. Recent HR-SEM (high-resolution scanning electron microscopy) analyses of nodules and crusts support their biogenic origin. Within the nodules, bacteria with surface S-layers are arranged on biofilm-like structures, around which Mn deposition starts. In crusts, coccoliths represent the dominant biologically formed structures that act as bio-seeds for an initial Mn deposition. In contrast, hydrothermal vents have apparently an abiogenic origin; however, their minerals are biogenically transformed by bacteria. In turn, strategies can now be developed for biotechnological enrichment as well as selective dissolution of metals from such concretions. We are convinced that the recent discoveries will considerably contribute to our understanding of the participation of organic matrices in the enrichment of those metals and will provide the basis for feasibility studies for biotechnological applications.

  6. Optimization by simulation of the nature of the buffer, the gap profile of the absorber and the thickness of the various layers in CZTSSe solar cells

    Science.gov (United States)

    Chadel, Meriem; Chadel, Asma; Moustafa Bouzaki, Mohammed; Aillerie, Michel; Benyoucef, Boumediene; Charles, Jean-Pierre

    2017-11-01

    Performances of ZnO/ZnS/CZTSSe polycrystalline thin film solar cells (Copper Zinc Tin Sulphur Selenium-solar cell) were simulated for different thicknesses of the absorber and ZnS buffer layers. Simulations were performed with SCAPS (Solar Cell Capacitance Simulator) software, starting with actual parameters available from industrial data for commercial cells processing. The influences of the thickness of the various layers in the structure of the solar cell and the gap profile of the CZTSSe absorber layer on the performance of the solar cell were studied in detail. Through considerations of recent works, we discuss possible routes to enhance the performance of CZTSSe solar cells towards a higher efficiency level. Thus, we found that for one specific thickness of the absorber layer, the efficiency of the CZTSSe solar cell can be increased when a ZnS layer replaces the usual CdS buffer layer. On the other hand, the efficiency of the solar cell can be also improved when the absorber layer presents a grad-gap. In this case, the maximum efficiency for the CZTSSe cell was found equal to 13.73%.

  7. Amplitude various angles (AVA) phenomena in thin layer reservoir: Case study of various reservoirs

    International Nuclear Information System (INIS)

    thfloor, Physics Dept., FMIPA, Institut Teknologi Bandung (Indonesia); Rock Fluid Imaging Lab., Bandung (Indonesia))" data-affiliation=" (Wave Inversion and Subsurface Fluid Imaging Research Laboratory (WISFIR), Basic Science Center A 4thfloor, Physics Dept., FMIPA, Institut Teknologi Bandung (Indonesia); Rock Fluid Imaging Lab., Bandung (Indonesia))" >Nurhandoko, Bagus Endar B.; Susilowati

    2015-01-01

    Amplitude various offset is widely used in petroleum exploration as well as in petroleum development field. Generally, phenomenon of amplitude in various angles assumes reservoir’s layer is quite thick. It also means that the wave is assumed as a very high frequency. But, in natural condition, the seismic wave is band limited and has quite low frequency. Therefore, topic about amplitude various angles in thin layer reservoir as well as low frequency assumption is important to be considered. Thin layer reservoir means the thickness of reservoir is about or less than quarter of wavelength. In this paper, I studied about the reflection phenomena in elastic wave which considering interference from thin layer reservoir and transmission wave. I applied Zoeppritz equation for modeling reflected wave of top reservoir, reflected wave of bottom reservoir, and also transmission elastic wave of reservoir. Results show that the phenomena of AVA in thin layer reservoir are frequency dependent. Thin layer reservoir causes interference between reflected wave of top reservoir and reflected wave of bottom reservoir. These phenomena are frequently neglected, however, in real practices. Even though, the impact of inattention in interference phenomena caused by thin layer in AVA may cause inaccurate reservoir characterization. The relation between classes of AVA reservoir and reservoir’s character are different when effect of ones in thin reservoir and ones in thick reservoir are compared. In this paper, I present some AVA phenomena including its cross plot in various thin reservoir types based on some rock physics data of Indonesia

  8. Capacitance Voltage of P3HT:Graphene Nanocomposites Based Bulk-Heterojunction Organic Solar Cells

    International Nuclear Information System (INIS)

    Mohd Shariff, Nur Shakina; Mohamad Saad, Puteri Sarah; Mahmood, Mohamad Rusop

    2015-01-01

    After the discovery of conjugated polymer and bulk-heterojunction concept, organic solar cell has gain many interest in the photovoltaic world. The main problem for organic solar cells is that the power conversion efficiency (PCE) is still considered low even though it is much more low cost compared to inorganic solar cell such as Silicon (Si). Therefore, the objective of this research is to investigate the effect of Poly(3-hexylthiophene) (P3HT) thickness and concentration towards the capacitance voltage of the P3HT:Graphene solar cells. A simulation software called SCAPS is used in this research to simulate the effect on the solar cells. SCAPS is specialized for photovoltaic simulation studies. The solar cell's structure will be drawn inside the simulation and the parameters for each layers is inserted. The voltage range will be fixed and the capacitance voltage will be calculated by the software and all the results will be put into one graph. For thickness results, P3HT's layer at a thickness of 100nm has the lowest value of capacitance and clearly shows a peak at 0.86V. Where for the concentration, 1×10 16 cm -3 is the only value that clearly shows there is the built-in voltage (V bi ) in the solar cells. Therefore, P3HT's thickness of 100 nm and concentration of 1×10 16 cm −3 has the best overall results. (paper)

  9. Survey on the phage resistance mechanisms displayed by a dairy Lactobacillus helveticus strain.

    Science.gov (United States)

    Zago, Miriam; Orrù, Luigi; Rossetti, Lia; Lamontanara, Antonella; Fornasari, Maria Emanuela; Bonvini, Barbara; Meucci, Aurora; Carminati, Domenico; Cattivelli, Luigi; Giraffa, Giorgio

    2017-09-01

    In this study the presence and functionality of phage defence mechanisms in Lactobacillus helveticus ATCC 10386, a strain of dairy origin which is sensitive to ΦLh56, were investigated. After exposure of ATCC 10386 to ΦLh56, the whole-genome sequences of ATCC 10386 and of a phage-resistant derivative (LhM3) were compared. LhM3 showed deletions in the S-layer protein and a higher expression of the genes involved in the restriction/modification (R/M) system. Genetic data were substantiated by measurements of bacteriophage adsorption rates, efficiency of plaquing, cell wall protein size and by gene expression analysis. In LhM3 two phage resistance mechanisms, the inhibition of phage adsorption and the upregulation of Type I R/M genes, take place and explain its resistance to ΦLh56. Although present in both ATCC 10386 and LhM3 genomes, the CRISPR machinery did not seem to play a role in the phage resistance of LhM3. Overall, the natural selection of phage resistant strains resulted successful in detecting variants carrying multiple phage defence mechanisms in L. helveticus. The concurrent presence of multiple phage-resistance systems should provide starter strains with increased fitness and robustness in dairy ecosystems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Rugged single domain antibody detection elements for Bacillus anthracis spores and vegetative cells.

    Directory of Open Access Journals (Sweden)

    Scott A Walper

    Full Text Available Significant efforts to develop both laboratory and field-based detection assays for an array of potential biological threats started well before the anthrax attacks of 2001 and have continued with renewed urgency following. While numerous assays and methods have been explored that are suitable for laboratory utilization, detection in the field is often complicated by requirements for functionality in austere environments, where limited cold-chain facilities exist. In an effort to overcome these assay limitations for Bacillus anthracis, one of the most recognizable threats, a series of single domain antibodies (sdAbs were isolated from a phage display library prepared from immunized llamas. Characterization of target specificity, affinity, and thermal stability was conducted for six sdAb families isolated from rounds of selection against the bacterial spore. The protein target for all six sdAb families was determined to be the S-layer protein EA1, which is present in both vegetative cells and bacterial spores. All of the sdAbs examined exhibited a high degree of specificity for the target bacterium and its spore, with affinities in the nanomolar range, and the ability to refold into functional antigen-binding molecules following several rounds of thermal denaturation and refolding. This research demonstrates the capabilities of these sdAbs and their potential for integration into current and developing assays and biosensors.

  11. Effects of Copaifera duckei Dwyer oleoresin on the cell wall and cell division of Bacillus cereus.

    Science.gov (United States)

    Gomes Dos Santos, Elizabeth Cristina; Donnici, Claudio Luis; Camargos, Elizabeth Ribeiro da Silva; Augusto de Rezende, Adriana; Andrade, Eloisa Helena de Aguiar; Soares, Luiz Alberto Lira; Farias, Luiz de Macêdo; Roque de Carvalho, Maria Auxiliadora; Almeida, Maria das Graças

    2013-07-01

    The aim of this work was to evaluate the antibacterial activity of Copaifera duckei oleoresin and to determine its possible mechanism of action against bacteria of clinical and food interest. The antibacterial activity was determined by agar diffusion and dilution methods; the mechanism of action by transmission electron microscopy and by SDS-PAGE; the bioactive compounds by bioautography; and the chemical analysis by GC/MS. Oleoresin showed activity against nine of the 11 strains of bacteria tested. Bacillus cereus was the most sensitive, with a MIC corresponding to 0.03125 mg ml(-1) and with a bactericidal action. Oleoresin acted on the bacterial cell wall, removing proteins and the S-layer, and interfering with the cell-division process. This activity probably can be attributed to the action of terpenic compounds, among them the bisabolene compound. Gram-negative bacteria tested were not inhibited. C. duckei oleoresin is a potential antibacterial, suggesting that this oil could be used as a therapeutic alternative, mainly against B. cereus.

  12. Wide-Gap Cu(In,Ga)Se2 Solar Cells with Zn(O,S) Buffer Layers Prepared by Atomic Layer Deposition

    Science.gov (United States)

    Nakashima, Kazuya; Kumazawa, Toyokazu; Kobayashi, Taizo; Mise, Takahiro; Nakada, Tokio

    2012-10-01

    Wide-gap Cu(In0.4,Ga0.6)Se2 solar cells with Zn(O,S) buffer layers deposited by atomic layer deposition (ALD) technique have been investigated. The band-gap energy (Eg) of the Zn(O,S) layer estimated by optical transmission and reflection measurements was varied from 3.2 to 3.6 eV. The solar cells with sulfur (S)-poor Zn(O,S) buffer layers showed a low open-circuit voltage (VOC) owing to the cliff nature of the conduction band offset (CBO). In contrast, the solar cells with S-rich Zn(O,S) buffer layers showed a low short-circuit current density (JSC) owing to the spike nature of CBO. Even if the CBO values were adequate, the best solar cell efficiencies were considerably low. These results suggest that the main cause for the low efficiencies is not interface recombination at the Zn(O,S)/Cu(In,Ga)Se2 interface, but mainly bulk recombination in the Cu(In,Ga)Se2 (CIGS) absorber layer.

  13. The Impacts of Islandness on the Urbanism and Architecture of Mombasa

    Directory of Open Access Journals (Sweden)

    Gerald Steyn

    2015-12-01

    Full Text Available Most of the Swahili port cities that occupied the western rim of the medieval Indian Ocean long-distance trading system were founded on islands. Dating from as early as the 10th century CE, Lamu and Zanzibar have become ‘museumified’ as World Heritage sites, while other island port cities, such as Kilwa and Pate, are now uninhabited ruins. Mombasa Island, however, despite numerous calamities, is an increasingly important commercial hub and gateway into East Africa. This study aims to determine how some intrinsic benefits of islandness have shaped the settlement patterns and architectural forms that embody this continuous process of urbanisation. A typological analysis serves to explore Mombasa Island’s layers of spatiality and morphology. More than any other East African city, this island reflects the synthesis of the distinctive settlement traditions of the Swahilis, Portuguese, Omanis and, subsequently, the British colonisers, through to its current state as a dynamic, modern urban centre. Compact, complex, and culturally diverse, its unique island concepts offer a wide range of contemporary urban and architectural solutions.

  14. Comparative genome analysis of Bacillus cereus group genomes withBacillus subtilis

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Iain; Sorokin, Alexei; Kapatral, Vinayak; Reznik, Gary; Bhattacharya, Anamitra; Mikhailova, Natalia; Burd, Henry; Joukov, Victor; Kaznadzey, Denis; Walunas, Theresa; D' Souza, Mark; Larsen, Niels; Pusch,Gordon; Liolios, Konstantinos; Grechkin, Yuri; Lapidus, Alla; Goltsman,Eugene; Chu, Lien; Fonstein, Michael; Ehrlich, S. Dusko; Overbeek, Ross; Kyrpides, Nikos; Ivanova, Natalia

    2005-09-14

    Genome features of the Bacillus cereus group genomes (representative strains of Bacillus cereus, Bacillus anthracis and Bacillus thuringiensis sub spp israelensis) were analyzed and compared with the Bacillus subtilis genome. A core set of 1,381 protein families among the four Bacillus genomes, with an additional set of 933 families common to the B. cereus group, was identified. Differences in signal transduction pathways, membrane transporters, cell surface structures, cell wall, and S-layer proteins suggesting differences in their phenotype were identified. The B. cereus group has signal transduction systems including a tyrosine kinase related to two-component system histidine kinases from B. subtilis. A model for regulation of the stress responsive sigma factor sigmaB in the B. cereus group different from the well studied regulation in B. subtilis has been proposed. Despite a high degree of chromosomal synteny among these genomes, significant differences in cell wall and spore coat proteins that contribute to the survival and adaptation in specific hosts has been identified.

  15. Facile synthesis of core/shell ZnO/ZnS nanofibers by electrospinning and gas-phase sulfidation for biosensor applications.

    Science.gov (United States)

    Baranowska-Korczyc, Anna; Sobczak, Kamil; Dłużewski, Piotr; Reszka, Anna; Kowalski, Bogdan J; Kłopotowski, Łukasz; Elbaum, Danek; Fronc, Krzysztof

    2015-10-07

    This study describes a new method of passivating ZnO nanofiber-based devices with a ZnS layer. This one-step process was carried out in H2S gas at room temperature, and resulted in the formation of core/shell ZnO/ZnS nanofibers. This study presents the structural, optical and electrical properties of ZnO/ZnS nanofibers formed by a 2 nm ZnS sphalerite crystal shell covering a 5 nm ZnO wurtzite crystal core. The passivation process prevented free carriers from capture by oxygen molecules and significantly reduced the impact of O2 on nanostructure conductivity. The conductivity of the nanofibers was increased by three orders of magnitude after the sulfidation, the photoresponse time was reduced from 1500 s to 30 s, and the cathodoluminescence intensity increased with the sulfidation time thanks to the removal of ZnO surface defects by passivation. The ZnO/ZnS nanofibers were stable in water for over 30 days, and in phosphate buffers of acidic, neutral and alkaline pH for over 3 days. The by-products of the passivation process did not affect the conductivity of the devices. The potential of ZnO/ZnS nanofibers for protein biosensing is demonstrated using biotin and streptavidin as a model system. The presented ZnS shell preparation method can facilitate the construction of future sensors and protects the ZnO surface from dissolving in a biological environment.

  16. Synthesis of Efficiently Green Luminescent CdSe/ZnS Nanocrystals Via Microfluidic Reaction

    Directory of Open Access Journals (Sweden)

    Luan Weiling

    2008-01-01

    Full Text Available AbstractQuantum dots with emission in the spectral region from 525 to 535 nm are of special interest for their application in green LEDs and white-light generation, where CdSe/ZnS core-shell structured nanocrystals (NCs are among promising candidates. In this study, triple-ligand system (trioctylphosphine oxide–oleic acid–oleylamine was designed to improve the stability of CdSe NCs during the early reaction stage. With the precisely controlled reaction temperature (285 °C and residence time (10 s by the recently introduced microfluidic reaction technology, green luminescent CdSe NCs (λ = 522 nm exhibiting narrow FWHM of PL (30 nm was reproducibly obtained. After that, CdSe/ZnS core-shell NCs were achieved with efficient luminescence in the pure green spectral region, which demonstrated high PL QY up to 70% and narrow PL FWHM as 30 nm. The strengthened mass and heat transfer in the microchannel allowed the formation of highly luminescent CdSe/ZnS NCs under low reaction temperature and short residence time (T = 120 °C,t = 10 s. The successful formation of ZnS layer was evidence of the substantial improvement of PL intensity, being further confirmed by XRD, HRTEM, and EDS study.

  17. Global responses of Methanococcus maripaludis to specific nutrient limitations and growth rate.

    Science.gov (United States)

    Hendrickson, Erik L; Liu, Yuchen; Rosas-Sandoval, Guillermina; Porat, Iris; Söll, Dieter; Whitman, William B; Leigh, John A

    2008-03-01

    Continuous culture, transcriptome arrays, and measurements of cellular amino acid pools and tRNA charging levels were used to determine the response of Methanococcus maripaludis to leucine limitation. For comparison, the responses to phosphate and H2 limitations were measured as well. In addition, the effect of growth rate was determined. Leucine limitation resulted in a broad response. tRNA(Leu) charging decreased, but only small increases in mRNA were seen for amino acid biosynthesis genes. However, the cellular levels of free isoleucine and valine showed significant increases, indicating a coordinate regulation of branched-chain amino acids at a post-mRNA level. Leucine limitation also resulted in increased mRNA abundance for ribosomal protein genes, increased rRNA abundance, and decreased mRNA abundance for genes of methanogenesis. In contrast, phosphate limitation induced a specific response, a marked increase in mRNA levels for a phosphate transporter. Some mRNA levels responded to more than one factor; for example, transcripts for flagellum synthesis genes decreased under conditions of leucine limitation and increased under H2 limitation. Increased growth rate resulted in increased mRNA levels for ribosomal protein genes, increased rRNA abundance, and increased mRNA for a gene encoding an S-layer protein.

  18. Fault zone characteristics and basin complexity in the southern Salton Trough, California

    Science.gov (United States)

    Persaud, Patricia; Ma, Yiran; Stock, Joann M.; Hole, John A.; Fuis, Gary S.; Han, Liang

    2016-01-01

    Ongoing oblique slip at the Pacific–North America plate boundary in the Salton Trough produced the Imperial Valley (California, USA), a seismically active area with deformation distributed across a complex network of exposed and buried faults. To better understand the shallow crustal structure in this region and the connectivity of faults and seismicity lineaments, we used data primarily from the Salton Seismic Imaging Project to construct a three-dimensional P-wave velocity model down to 8 km depth and a velocity profile to 15 km depth, both at 1 km grid spacing. A VP = 5.65–5.85 km/s layer of possibly metamorphosed sediments within, and crystalline basement outside, the valley is locally as thick as 5 km, but is thickest and deepest in fault zones and near seismicity lineaments, suggesting a causative relationship between the low velocities and faulting. Both seismicity lineaments and surface faults control the structural architecture of the western part of the larger wedge-shaped basin, where two deep subbasins are located. We estimate basement depths, and show that high velocities at shallow depths and possible basement highs characterize the geothermal areas.

  19. CdS/CdSe lateral heterostructure nanobelts by a two-step physical vapor transport method

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yu Lee; Jung, Jae Hun; Yoon, Hyun Sik; Song, Man Suk; Bae, Se Hwan; Kim, Yong [Department of Physics, Dong-A University, Hadan-2-dong, Sahagu, Busan 604-714 (Korea, Republic of); Chen Zhigang; Zou Jin [Materials Engineering and Center of Microscopy and Microanalysis, University of Queensland, Brisbane, QLD 4072 (Australia); Joyce, Hannah J; Gao Qiang; Tan, Hark Hoe; Jagadish, Chennupati, E-mail: yongkim@dau.ac.kr [Department of Electronic Materials Engineering, Research School of Physics and Engineering, Australian National University, Canberra, ACT 0200 (Australia)

    2010-04-09

    The two-dimensional heterostructure nanobelts with a central CdSe region and lateral CdS structures are synthesized by a two-step physical vapor transport method. The large growth rate difference between lateral CdS structures on both {+-} (0001) sides of the CdSe region is found. The growth anisotropy is discussed in terms of the polar nature of the side {+-} (0001) surfaces of CdSe. High-resolution transmission electron microscopy reveals the CdSe central region covered with non-uniform CdS layer/islands. From micro-photoluminescence measurements, a systematic blueshift of emission energy from the central CdSe region in accordance with the increase of lateral CdS growth temperature is observed. This result indicates that the intermixing rate in the CdSe region with CdS increases with the increase of lateral CdS growth temperature. In conventional CdSSe ternary nanostructures, morphology and emission wavelength were correlated parameters. However, the morphology and emission wavelength are independently controllable in the CdS/CdSe lateral heterostructure nanobelts. This structure is attractive for applications in visible optoelectronic devices.

  20. Development of a SaaS application probe to the physical properties of the Earth's interior: An attempt at moving HPC to the cloud

    Science.gov (United States)

    Huang, Qian

    2014-09-01

    Scientific computing often requires the availability of a massive number of computers for performing large-scale simulations, and computing in mineral physics is no exception. In order to investigate physical properties of minerals at extreme conditions in computational mineral physics, parallel computing technology is used to speed up the performance by utilizing multiple computer resources to process a computational task simultaneously thereby greatly reducing computation time. Traditionally, parallel computing has been addressed by using High Performance Computing (HPC) solutions and installed facilities such as clusters and super computers. Today, it has been seen that there is a tremendous growth in cloud computing. Infrastructure as a Service (IaaS), the on-demand and pay-as-you-go model, creates a flexible and cost-effective mean to access computing resources. In this paper, a feasibility report of HPC on a cloud infrastructure is presented. It is found that current cloud services in IaaS layer still need to improve performance to be useful to research projects. On the other hand, Software as a Service (SaaS), another type of cloud computing, is introduced into an HPC system for computing in mineral physics, and an application of which is developed. In this paper, an overall description of this SaaS application is presented. This contribution can promote cloud application development in computational mineral physics, and cross-disciplinary studies.

  1. Dead zones in colloidal quantum dot photovoltaics: evidence and implications

    KAUST Repository

    Barkhouse, D. Aaron R.

    2010-09-01

    In order to fabricate photovoltaic (PV) cells incorporating light-trapping electrodes, flexible foil substrates, or more than one junction, illumination through the top-contact (i.e.: non-substrate) side of a photovoltaic device is desirable. We investigate the relative collection efficiency for illumination through the top vs. bottom of PbS colloidal quantum dot (CQD) PV devices. The external quantum efficiency spectra of FTO/TiO2/PbS CQD/ITO PV devices with various PbS layer thicknesses were measured for illumination through either the top (ITO) or bottom (FTO) contacts. By comparing the relative shapes and intensities of these spectra with those calculated from an estimation of the carrier generation profile and the internal quantum efficiency as a function of distance from the TiO2 interface in the devices, a substantial dead zone, where carrier extraction is dramatically reduced, is identified near the ITO top contact. The implications for device design, and possible means of avoiding the formation of such a dead zone, are discussed.

  2. Superconductivity and magnetism in iron sulfides intercalated by metal hydroxides.

    Science.gov (United States)

    Zhou, Xiuquan; Eckberg, Christopher; Wilfong, Brandon; Liou, Sz-Chian; Vivanco, Hector K; Paglione, Johnpierre; Rodriguez, Efrain E

    2017-05-01

    Inspired by naturally occurring sulfide minerals, we present a new family of iron-based superconductors. A metastable form of FeS known as the mineral mackinawite forms two-dimensional sheets that can be readily intercalated by various cationic guest species. Under hydrothermal conditions using alkali metal hydroxides, we prepare three different cation and metal hydroxide-intercalated FeS phases including (Li 1- x Fe x OH)FeS, [(Na 1- x Fe x )(OH) 2 ]FeS, and K x Fe 2- y S 2 . Upon successful intercalation of the FeS layer, the superconducting critical temperature T c of mackinawite is enhanced from 5 K to 8 K for the (Li 1- x Fe x OH) δ + intercalate. Layered heterostructures of [(Na 1- x Fe x )(OH) 2 ]FeS resemble the natural mineral tochilinite, which contains an iron square lattice interleaved with a hexagonal hydroxide lattice. Whilst heterostructured [(Na 1- x Fe x )(OH) 2 ]FeS displays long-range magnetic ordering near 15 K, K x Fe 2- y S 2 displays short range antiferromagnetism.

  3. Proximity effect between a ferromagnetic insulator and a superconductor

    Energy Technology Data Exchange (ETDEWEB)

    Wolf, Michael J.; Beckmann, Detlef [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Nanotechnologie; Huebler, Florian [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Nanotechnologie; Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Festkoerperphysik; Suergers, Christoph [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Physikalisches Inst.; Loehneysen, Hilbert von [Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Inst. fuer Festkoerperphysik; Karlsruher Institut fuer Technologie (KIT), Karlsruhe (Germany). Physikalisches Inst.

    2012-07-01

    Electron transfer through spin-active interfaces can be modeled by the transmission amplitudes and a relative phase shift between spin-up and spin-down wavefunctions, the spin-mixing angle. Recently, Andreev bound states have been observed in F/S tunnel contacts which imply a non-zero spin-mixing angle of the ultrathin F/S barrier. In order to separate the spin-active interface from the detector tunnel contact, we have fabricated normal metal/superconductor tunnel contacts on top of a ferromagnetic insulator. We prepared EuS thin films (d{approx}20 nm) on top of Si(111) substrates by means of e-beam evaporation and created Al/Al-Oxide/Cu tunnel contacts by means of shadow evaporation. In an applied magnetic field, the tunnel spectra show an enhanced Zeeman splitting which is due to the presence of the exchange field of the EuS layer. Furthermore, we observe small peaks in the subgap region of the tunnel spectra which may be attributed to Andreev bound states due to a non-zero spin-mixing angle at the EuS/Al interface. The results suggest the use of EuS thin films for generating equal-spin triplet superconductivity.

  4. Heterologous expression of carcinoembryonic antigen in Lactococcus lactis via LcsB-mediated surface displaying system for oral vaccine development.

    Science.gov (United States)

    Zhang, Xiaowei; Hu, Shumin; Du, Xue; Li, Tiejun; Han, Lanlan; Kong, Jian

    2016-12-01

    Carcinoembryonic antigen (CEA) is an attractive target for immunotherapy because it is expressed minimally in normal tissue, but is overexpressed in a wide variety of malignant epithelial tissues. Lactic acid bacteria (LABs), widely used in food processes, are attractive candidates for oral vaccination. Thus, we examined whether LABs could be used as a live vaccine vector to deliver CEA antigen. CEA was cloned into an Escherichia coli/Lactococcus lactis shuttle vector pSEC:LEISS under the control of a nisin promoter. For displaying the CEA on the cell surface of the L. lactis strain, the anchor motif LcsB from the S-layer protein of Lactobacillus crispatus was fused with CEA. Intracellular and cell surface expression of the CEA-LcsB fusion was confirmed by western blot analysis. Significantly higher levels of CEA-specific secretory immunoglobulin A in the sera of mice were observed upon oral administration of strain cultures containing the CEA-LcsB fused protein. In addition, the CEA-LcsB antigen group showed a higher spleen index compared to the CEA antigen alone or negative control, demonstrating that surface-displayed CEA antigen could induce a higher immune response. These results provided the first evidence for displaying CEA antigen on the cell surfaces of LABs as oral vaccines against cancer or infectious diseases. Copyright © 2014. Published by Elsevier B.V.

  5. Corrosion of Fe-(9~37 wt. %Cr Alloys at 700–800 °C in (N2, H2O, H2S-Mixed Gas

    Directory of Open Access Journals (Sweden)

    Min Jung Kim

    2016-11-01

    Full Text Available Fe-(9, 19, 28, 37 wt. %Cr alloys were corroded at 700 and 800 °C for 70 h under 1 atm of N2, 1 atm of N2/3.2%H2O mixed gas, and 1 atm of N2/3.1%H2O/2.42%H2S mixed gas. In this gas composition order, the corrosion rate of Fe-9Cr alloy rapidly increased. Fe-9Cr alloy was always non-protective. In contrast, Fe-(19, 28, 37 wt. %Cr alloys were protective in N2 and N2/3.2%H2O mixed gas because of the formation of the Cr2O3 layer. They, however, became nonprotective in N2/3.1%H2O/2.42%H2S mixed gas because sulfidation dominated to form the outer FeS layer and the inner Cr2S3 layer containing some FeCr2S4.

  6. New electroluminescent-semiconductor X-Ray detector

    International Nuclear Information System (INIS)

    Vlasenko, N.A.; Kononets, Y.F.; Veligura, L.I.; Braylovsky, E.Y.; Berdnichenko, P.E.; Berdnichenko, S.V.; Kuts, V.I.; Tsyrkunov, Y.A.

    1999-01-01

    X-ray detectors capable of visualization of the spatial distribution of the radiation field are interesting for many applications, especially in medicine. In 50's the attention of researchers has been attracted to the detectors based on a powder electroluminescent (EL) phosphor (e.g. ZnS:Cu) connected in series with a semiconductors (S) sensitive to X-ray (e.g. thick-film CdS) [1,2]. Impedance of the two chosen so that the voltage drop on the EL layer is insufficient to excite electroluminescence in darkness (without X-rays). Under action of X-rays the S-layer resistance is decreased and, as consequence, the voltage on the phosphor increases and EL emission with the intensity dependent on X-ray dose rate arises. However, these 'EL-S' detectors did not of use due to the slow response (several seconds), instability, and low picture contrast. To improve these characteristics, a new variant of the EL-S detector has been studied in this paper. The novelty consists in the use of a thin-film electroluminescent structure (TFELS) and a semiconductor wafer instead of a powder and thick-film layers used earlier. (authors)

  7. Vortex Flipping in Superconductor-Ferromagnet Spin Valve Structures

    Science.gov (United States)

    Patino, Edgar J.; Aprili, Marco; Blamire, Mark; Maeno, Yoshiteru

    2014-03-01

    We report in plane magnetization measurements on Ni/Nb/Ni/CoO and Co/Nb/Co/CoO spin valve structures with one of the ferromagnetic layers pinned by an antiferromagnetic layer. In samples with Ni, below the superconducting transition Tc, our results show strong evidence of vortex flipping driven by the ferromagnets magnetization. This is a direct consequence of proximity effect that leads to vortex supercurrents leakage into the ferromagnets. Here the polarized electron spins are subject to vortices magnetic field occasioning vortex flipping. Such novel mechanism has been made possible for the first time by fabrication of the F/S/F/AF multilayered spin valves with a thin-enough S layer to barely confine vortices inside as well as thin-enough F layers to align and control the magnetization within the plane. When Co is used there is no observation of vortex flipping effect. This is attributed to Co shorter coherence length. Interestingly instead a reduction in pinning field of about 400 Oe is observed when the Nb layer is in superconducting state. This effect cannot be explained in terms of vortex fields. In view of these facts any explanation must be directly related to proximity effect and thus a remarkable phenomenon that deserves further investigation. Programa Nacional de Ciencias Basicas COLCIENCIAS (No. 120452128168).

  8. Sequential electro-deposition of Bi{sub 2}S{sub 3}/CdS films as co-sensitizer photoanodes for liquid junction solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Jana, Atanu; Hazra, Prasenjit; Hazra, Mukul; Datta, Jayati, E-mail: jayati_datta@rediffmail.com

    2016-11-01

    In this investigation multilayered conjugate films are formulated with Bi{sub 2}S{sub 3} and CdS nanoparticles (NPs) on FTO glass substrate. Thin layer Bi{sub 2}S{sub 3} was deposited and subsequently covered with various levels of CdS coating. Optical properties and XRD analysis of the films show existence of both the compound phases. The morphology of the films studied through electron microscopy reveals coverage of spherical CdS NPs on the network of Bi{sub 2}S{sub 3} NPs. The electrochemical impedance records and performances output characteristics of the n-type films show that the most efficient co-sensitizer matrix is produced with deep coating of CdS on thin layer of Bi{sub 2}S{sub 3}. - Highlights: • Multilayered Bi{sub 2}S{sub 3}/CdS conjugate films are formulated on FTO glass substrate. • Photo-degradation of Bi{sub 2}S{sub 3} is restricted by the coating of CdS layer. • High level of Cd coating on thin layer of Bi{sub 2}S{sub 3} have shown appreciable photocurrent output. • Photo-conversion efficiency of 0.93% is observed for the best conjugate film.

  9. Detailed investigation of the bifurcation diagram of capacitively coupled Josephson junctions in high-Tc superconductors and its self similarity

    Science.gov (United States)

    Hamdipour, Mohammad

    2018-04-01

    We study an array of coupled Josephson junction of superconductor/insulator/superconductor type (SIS junction) as a model for high temperature superconductors with layered structure. In the current-voltage characteristics of this system there is a breakpoint region in which a net electric charge appear on superconducting layers, S-layers, of junctions which motivate us to study the charge dynamics in this region. In this paper first of all we show a current voltage characteristics (CVC) of Intrinsic Josephson Junctions (IJJs) with N=3 Junctions, then we show the breakpoint region in that CVC, then we try to investigate the chaos in this region. We will see that at the end of the breakpoint region, behavior of the system is chaotic and Lyapunov exponent become positive. We also study the route by which the system become chaotic and will see this route is bifurcation. Next goal of this paper is to show the self similarity in the bifurcation diagram of the system and detailed analysis of bifurcation diagram.

  10. Magnetism at the Interface of Magnetic Oxide and Nonmagnetic Semiconductor Quantum Dots.

    Science.gov (United States)

    Saha, Avijit; Viswanatha, Ranjani

    2017-03-28

    Engineering interfaces specifically in quantum dot (QD) heterostructures provide several prospects for developing multifunctional building block materials. Precise control over internal structure by chemical synthesis offers a combination of different properties in QDs and allows us to study their fundamental properties, depending on their structure. Herein, we studied the interface of magnetic/nonmagnetic Fe 3 O 4 /CdS QD heterostructures. In this work, we demonstrate the decrease in the size of the magnetic core due to annealing at high temperature by the decrease in saturation magnetization and blocking temperature. Furthermore, surprisingly, in a prominently optically active and magnetically inactive material such as CdS, we observe the presence of substantial exchange bias in spite of the nonmagnetic nature of CdS QDs. The presence of exchange bias was proven by the increase in magnetic anisotropy as well as the presence of exchange bias field (H E ) during the field-cooled magnetic measurements. This exchange coupling was eventually traced to the in situ formation of a thin antiferromagnetic FeS layer at the interface. This is verified by the study of Fe local structure using X-ray absorption fine structure spectroscopy, demonstrating the importance of interface engineering in QDs.

  11. Half-metallic superconducting triplet spin multivalves

    Science.gov (United States)

    Alidoust, Mohammad; Halterman, Klaus

    2018-02-01

    We study spin switching effects in finite-size superconducting multivalve structures. We examine F1F2SF3 and F1F2SF3F4 hybrids where a singlet superconductor (S) layer is sandwiched among ferromagnet (F) layers with differing thicknesses and magnetization orientations. Our results reveal a considerable number of experimentally viable spin-valve configurations that lead to on-off switching of the superconducting state. For S widths on the order of the superconducting coherence length ξ0, noncollinear magnetization orientations in adjacent F layers with multiple spin axes leads to a rich variety of triplet spin-valve effects. Motivated by recent experiments, we focus on samples where the magnetizations in the F1 and F4 layers exist in a fully spin-polarized half-metallic phase, and calculate the superconducting transition temperature, spatially and energy resolved density of states, and the spin-singlet and spin-triplet superconducting correlations. Our findings demonstrate that superconductivity in these devices can be completely switched on or off over a wide range of magnetization misalignment angles due to the generation of equal-spin and opposite-spin triplet pairings.

  12. Improved growth of solution-deposited thin films on polycrystalline Cu(In,Ga)Se{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Witte, Wolfram; Hariskos, Dimitrios [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), 70565, Stuttgart (Germany); Abou-Ras, Daniel [Helmholtz-Zentrum Berlin fuer Materialien und Energie, 14109, Berlin (Germany)

    2016-04-15

    CdS and Zn(O,S) grown by chemical bath deposition (CBD) are well established buffer materials for Cu(In,Ga)Se{sub 2} (CIGS) solar cells. As recently reported, a non-contiguous coverage of CBD buffers on CIGS grains with {112} surfaces can be detected, which was explained in terms of low surface energies of the {112} facets, leading to deteriorated wetting of the chemical solution on the CIGS surface. In the present contribution, we report on the effect of air annealing of CIGS thin films prior to the CBD of CdS and Zn(O,S) layers. In contrast to the growth on the as-grown CIGS layers, these buffer lay- ers grow densely on the annealed CIGS layer, even on grains with {112} surfaces. We explain the different growth behavior by increased surface energies of CIGS grains due to the annealing step, i.e., due to oxidation of the CIGS surface. Reference solar cells were processed and completed by i-ZnO/ZnO:Al layers for CdS and by (Zn,Mg)O/ZnO:Al for Zn(O,S) buffers. For solar cells with both, CdS and Zn(O,S) buffers, air-annealed CIGS films with improved buffer coverage resulted in higher power-conversion efficiencies, as compared with the devices containing as-grown CIGS layers. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Measurement of geo electric and radon intensity on determination of potential area for ground water drilling at Lebeng Barat village, Pasongsongan, East Java

    International Nuclear Information System (INIS)

    I Gde Sukadana

    2013-01-01

    Lebeng Barat village, Pasongsongan sub-district is a village which has insufficient of fresh water, particularly in dry season. This region has a fairly dense population and equitable distribution of the population, therefore a sufficient supply of clean water for consumption and other needs are required. The purpose of study is to find out the ground-water potential zone in determination of exploration drilling points to develop ground-water’s well production. The methods used in this study as follow: Geological/hydrogeological mapping, measurement of radon intensity and geo-electric sounding survey with Schlumberger’s configuration. Exposed rocks within work areas can be classified into 5 (five) rocks unit, namely clay stone with intercalation of limestone unit, inter bedded of calcareous sandstone and limestone unit, mud stone unit and limestone-clay stone unit. The potential rock’s layer as aquifer is a layer of calcareous sandstone which has characteristic of pale yellow to brown, medium-coarse grained, sufficient permeability rocks (in the section exposed at the surface) include the limestone unit. Rock aquifers that serve on the bottom are included in inter bedded of calcareous sandstone and limestone unit. Potential points recommended for drilling exploration / production are the point of LBR-29 with the thickness of the aquifer 1 (shallower) 33.86 m and aquifer 2 (deeper) 23.72 m. (author)

  14. Impact of a Strong Magnetic Storm and Two X-Ray Flares on the Ionospheric HF Channel in the Summer Solstice of 2015 According to Oblique Sounding in the Eurasian Region

    Science.gov (United States)

    Uryadov, V. P.; Kolchev, A. A.; Vertogradov, G. G.; Vybornov, F. I.; Egoshin, I. A.; Sklyarevsky, M. S.; Shumaev, V. V.; Chernov, A. G.

    2017-10-01

    We present the results of observations of the impact a strong magnetic storm and two X-ray flares in the summer solstice of 2015 on the HF signal characteristics during oblique sounding of the ionosphere in the Eurasian region. It was found that the negative phase of the magnetic storm led to a strong degradation of the ionospheric channel, up to a long blackout on the paths adjacent to the subauroral latitudes. On the midlatitude paths, a decrease in the maximum observable frequency of the F layer reached 50% with respect to the average values for an undisturbed ionosphere. The propagation velocity of the negative phase of a disturbance from the subauroral to the midlatitude ionosphere is determined (it is equal to about 100 m/s). It is shown that during a magnetic storm the least observable frequency and the average signal-to-noise ratio for the propagation mode via the sporadic E s layer correlate well with the auroral AE index. Anomalous signals were detected in the main phase of the magnetic storm on the Cyprus—Rostov-on-Don path when a chirp ionosonde-radio direction finder was operated in the over-the-horizon HF radar mode. On the basis of modeling and comparison with experimental data, it is shown that the anomalous signals are due to scattering of radio waves by small-scale irregularities located in the subauroral ionospheric F region.

  15. Atomic layer deposition of absorbing thin films on nanostructured electrodes for short-wavelength infrared photosensing

    International Nuclear Information System (INIS)

    Xu, Jixian; Sutherland, Brandon R.; Hoogland, Sjoerd; Fan, Fengjia; Sargent, Edward H.; Kinge, Sachin

    2015-01-01

    Atomic layer deposition (ALD), prized for its high-quality thin-film formation in the absence of high temperature or high vacuum, has become an industry standard for the large-area deposition of a wide array of oxide materials. Recently, it has shown promise in the formation of nanocrystalline sulfide films. Here, we demonstrate the viability of ALD lead sulfide for photodetection. Leveraging the conformal capabilities of ALD, we enhance the absorption without compromising the extraction efficiency in the absorbing layer by utilizing a ZnO nanowire electrode. The nanowires are first coated with a thin shunt-preventing TiO 2 layer, followed by an infrared-active ALD PbS layer for photosensing. The ALD PbS photodetector exhibits a peak responsivity of 10 −2  A W −1 and a shot-derived specific detectivity of 3 × 10 9  Jones at 1530 nm wavelength

  16. Graphene-based three-dimensional hierarchical sandwich-type architecture for high-performance Li/S batteries.

    Science.gov (United States)

    Chen, Renjie; Zhao, Teng; Lu, Jun; Wu, Feng; Li, Li; Chen, Junzheng; Tan, Guoqiang; Ye, Yusheng; Amine, Khalil

    2013-10-09

    A multiwalled carbon nanotube/sulfur (MWCNT@S) composite with core-shell structure was successfully embedded into the interlay galleries of graphene sheets (GS) through a facile two-step assembly process. Scanning and transmission electron microscopy images reveal a 3D hierarchical sandwich-type architecture of the composite GS-MWCNT@S. The thickness of the S layer on the MWCNTs is ~20 nm. Raman spectroscopy, X-ray diffraction, thermogravimetric analysis, and energy-dispersive X-ray analysis confirm that the sulfur in the composite is highly crystalline with a mass loading up to 70% of the composite. This composite is evaluated as a cathode material for Li/S batteries. The GS-MWCNT@S composite exhibits a high initial capacity of 1396 mAh/g at a current density of 0.2C (1C = 1672 mA/g), corresponding to 83% usage of the sulfur active material. Much improved cycling stability and rate capability are achieved for the GS-MWCNT@S composite cathode compared with the composite lacking GS or MWCNT. The superior electrochemical performance of the GS-MWCNT@S composite is mainly attributed to the synergistic effects of GS and MWCNTs, which provide a 3D conductive network for electron transfer, open channels for ion diffusion, strong confinement of soluble polysulfides, and effective buffer for volume expansion of the S cathode during discharge.

  17. CuNi/Nb S-F hybrid heterostructures for investigation of induced magnetization in superconducting layer

    International Nuclear Information System (INIS)

    Khaydukov, Yu.; Kim, J.-H.; Logvenov, G.; Morari, R.; Babakova, E.; Sidorenko, A.

    2013-01-01

    The mutual influence of the magnetism and superconductivity in superconductor/ferromagnet (S/F) nano fabricated thin films hybrid heterostructures has been an exciting topic in solid-state physics during last decade. However, the interesting theoretical predictions still wait for unambiguous experimental verification. One of such effect is the so-called spin screening (often called inverse proximity effect), which designates a spin polarization in the superconducting layer close to the S/F interface. It is theoretically shown that a spin polarization develops in the S layer with direction opposite to the spin polarization of the conduction electrons in the F layer. If the thicknesses of the ferromagnetic and superconducting layers are small compared to the London penetration length, then the orbital effect, caused by Meissner screening currents of superconductor will be small compared to the spin effect due to spin polarization. The thickness of the spin polarized sub-layer is comparable to the coherence length ξ of the superconductor. Therefore an advanced technology should be used for fabrication of S/F nanostructures with thin superconducting layers. (authors)

  18. Application of Electric Capacity Measurements to Detecting Delamination in Blades of Helicopter’s Lifting and Auxiliary Rotors

    Directory of Open Access Journals (Sweden)

    Gębura Andrzej

    2017-06-01

    Full Text Available This paper represents a series of the authors’ publications concerning effects of atmospheric conditions on aircraft [5-6, 11]. Hazards connected with separation ( delamination of heating elements from blade’s spar , namely: increased susceptibility to ice formation as a result of change in aerodynamic profile, decreased deicing effectiveness, shortened life of heating elements , weakened strength of blade’s structure, are described. In order to monitor the above mentioned delamination process during its early phase, these authors proposed to measure systematically electric capacity between the heating element and blade’s spar by means of a technical method. The electric capacity measurements performed by these authors on blades both in laboratory and service conditions demonstrated their practical usefulness for assessing delamination extent as well as for identifying areas where heating element separation from spar occurred. The method in question is simple , cheap , fast and non-interferring (non-destructive as well as it does not require dismounting the blades off the helicopter. As proved in practice , it is especially useful in sea-rescue or military operational conditions. Special attention was paid to application of the method to composite blades where coming-off the heating element tape causes local overheating the blade structure , that impairs flexibility of composite’s layers and may lead even to local cracks which may trigger helicopter crash. These authors desire to apply the method as a standard unit of on-board diagnostic system in the future.

  19. Electron holography of biological samples.

    Science.gov (United States)

    Simon, P; Lichte, H; Formanek, P; Lehmann, M; Huhle, R; Carrillo-Cabrera, W; Harscher, A; Ehrlich, H

    2008-01-01

    In this paper, we summarise the development of off-axis electron holography on biological samples starting in 1986 with the first results on ferritin from the group of Tonomura. In the middle of the 1990s strong interest was evoked, but then stagnation took place because the results obtained at that stage did not reach the contrast and the resolution achieved by conventional electron microscopy. To date, there exist only a few ( approximately 12) publications on electron holography of biological objects, thus this topic is quite small and concise. The reason for this could be that holography is mostly established in materials science by physicists. Therefore, applications for off-axis holography were powerfully pushed forward in the area of imaging, e.g. electric or magnetic micro- and nanofields. Unstained biological systems investigated by means of off-axis electron holography up to now are ferritin, tobacco mosaic virus, a bacterial flagellum, T5 bacteriophage virus, hexagonal packed intermediate layer of bacteria and the Semliki Forest virus. New results of the authors on collagen fibres and surface layer of bacteria, the so-called S-layer 2D crystal lattice are presented in this review. For the sake of completeness, we will shortly discuss in-line holography of biological samples and off-axis holography of materials related to biological systems, such as biomaterial composites or magnetotactic bacteria.

  20. Processing of semiconductors and thin film solar cells using electroplating

    Science.gov (United States)

    Madugu, Mohammad Lamido

    The global need for a clean, sustainable and affordable source of energy has triggered extensive research especially in renewable energy sources. In this sector, photovoltaic has been identified as a cheapest, clean and reliable source of energy. It would be of interest to obtain photovoltaic material in thin film form by using simple and inexpensive semiconductor growth technique such as electroplating. Using this growth technique, four semiconductor materials were electroplated on glass/fluorine-doped tin oxide (FTO) substrate from aqueous electrolytes. These semiconductors are indium selenide (In[x]Sey), zinc sulphide (ZnS), cadmium sulphide (CdS) and cadmium telluride (CdTe). In[x]Se[y] and ZnS were incorporated as buffer layers while CdS and CdTe layers were utilised as window and absorber layers respectively. All materials were grown using two-electrode (2E) system except for CdTe which was grown using 3E and 2E systems for comparison. To fully optimise the growth conditions, the as-deposited and annealed layers from all the materials were characterised for their structural, morphological, optical, electrical and defects structures using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), optical absorption (UV-Vis spectroscopy), photoelectrochemical (PEC) cell measurements, current-voltage (I-V), capacitance-voltage (C-V), DC electrical measurements, ultraviolet photoelectron spectroscopy (UPS) and photoluminescence (PL) techniques. Results show that InxSey and ZnS layers were amorphous in nature and exhibit both n-type and p-type in electrical conduction. CdS layers are n-type in electrical conduction and show hexagonal and cubic phases in both the as-deposited and after annealing process. CdTe layers show cubic phase structure with both n-type and p-type in electrical conduction. CdTe-based solar cell structures with a n-n heterojunction plus large Schottky barrier, as well as multi-layer graded

  1. Cu2ZnGeS4 thin films deposited by thermal evaporation: the impact of Ge concentration on physical properties

    Science.gov (United States)

    Courel, Maykel; Sanchez, T. G.; Mathews, N. R.; Mathew, X.

    2018-03-01

    In this work, the processing of Cu2ZnGeS4 (CZGS) thin films by a thermal evaporation technique starting from CuS, GeS and ZnS precursors, and post-deposition thermal processing, is discussed. Batches of films with GeS layers of varying thicknesses are deposited in order to study the role of Ge concentration on the structural, morphological, optical and electrical properties of CZGS films. The formation of the CZGS compound with a tetragonal phase and a kesterite structure is confirmed for all samples using XRD and Raman studies. An improvement in crystallite size for Ge-poor films is also observed in the XRD analysis, which is in good agreement with the grain size observed in the cross section SEM image. Furthermore, it is found that the band-gap of CZGS film can be tailored in the range of 2.0–2.23 eV by varying Ge concentration. A comprehensive electrical characterization is also performed which demonstrates that slightly Ge-poor samples are described by the lowest grain boundary defect densities and the highest photosensitivity and mobility values. A study of the work function of CZGS samples with different Ge concentrations is also presented. Finally, a theoretical evaluation is presented, considering, under ideal conditions, the possible impact of these films on device performance. Based on the characterization results, it is concluded that Ge-poor CZGS samples deposited by thermal evaporation present better physical properties for device applications.

  2. The PorX Response Regulator of the Porphyromonas gingivalis PorXY Two-Component System Does Not Directly Regulate the Type IX Secretion Genes but Binds the PorL Subunit

    Science.gov (United States)

    Vincent, Maxence S.; Durand, Eric; Cascales, Eric

    2016-01-01

    The Type IX secretion system (T9SS) is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion or cell surface exposition of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY, and PorX encode typical two-component system (TCS) sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN, and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we demonstrate that PorX does not bind T9SS gene promoters and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS. PMID:27630829

  3. The PorX response regulator of the Porphyromonas gingivalis PorXY two-component system does not directly regulate the Type IX secretion genes but binds the PorL subunit.

    Directory of Open Access Journals (Sweden)

    Maxence S Vincent

    2016-08-01

    Full Text Available The Type IX secretion system (T9SS is a versatile multi-protein complex restricted to bacteria of the Bacteriodetes phylum and responsible for the secretion of surface attachment of diverse proteins that participate to S-layer formation, gliding motility or pathogenesis. The T9SS is poorly characterized but a number of proteins involved in the assembly of the secretion apparatus in the oral pathogen Porphyromonas gingivalis have been identified based on genome substractive analyses. Among these proteins, PorY and PorX encode typical two-component system (TCS sensor and CheY-like response regulator respectively. Although the porX and porY genes do not localize at the same genetic locus, it has been proposed that PorXY form a bona fide TCS. Deletion of the porX in P. gingivalis causes a slight decrease of the expression of a number of other T9SS genes, including sov, porT, porP, porK, porL, porM, porN and porY. Here, we show that PorX and the soluble cytoplasmic domain of PorY interact. Using electrophoretic mobility shift, DNA-protein co-purification and heterologous host expression assays, we showed that PorX does not bind and does not directly regulate expression of the T9SS genes. Finally, we show that PorX interacts with the cytoplasmic domain of PorL, a component of the T9SS membrane core complex and propose that the CheY-like PorX protein might be involved in the dynamics of the T9SS.

  4. High and stable photoelectrochemical activity of ZnO/ZnSe/CdSe/Cu(x)S core-shell nanowire arrays: nanoporous surface with Cu(x)S as a hole mediator.

    Science.gov (United States)

    Ouyang, Wei-Xin; Yu, Yu-Xiang; Zhang, Wei-De

    2015-06-14

    Advanced materials for electrocatalytic and photoelectrochemical water splitting are key for taking advantage of renewable energy. In this study, ZnO/ZnSe/CdSe/Cu(x)S core-shell nanowire arrays with a nanoporous surface were fabricated via ion exchange and successive ionic layer adsorption and reaction (SILAR) processes. The ZnO/ZnSe/CdSe/Cu(x)S sample displays a high photocurrent density of 12.0 mA cm(-2) under AM 1.5G illumination, achieves the highest IPCE value of 89.5% at 500 nm at a bias potential of 0.2 V versus Ag/AgCl, and exhibits greatly improved photostability. The functions of the ZnSe, CdSe, and Cu(x)S layers in the ZnO/ZnSe/CdSe/Cu(x)S heterostructure were clarified. ZnSe is used as a passivation layer to reduce the trapping and recombination of charge carriers at the interfaces of the semiconductors. CdSe functions as a highly efficient visible light absorber and builds heterojunctions with the other components to improve the separation and transportation of the photoinduced electrons and holes. Cu(x)S serves as a passivation layer and an effective p-type hole mediator, which passivates the defects and surface states of the semiconductors and forms p-n junctions with CdSe to promote the hole transportation at the semiconductor-electrolyte interface. The nanoporous surface of the ZnO/ZnSe/CdSe/Cu(x)S core-shell nanowire arrays, together with the tunnel transportation of the charge carriers in the thin films of ZnSe and CdSe, also facilitates the kinetics of photoelectrochemical reactions and improves the optical absorption as well.

  5. Low temperature pulsed direct current magnetron sputtering technique for single phase β-In2S3 buffer layers for solar cell applications

    Science.gov (United States)

    Karthikeyan, Sreejith; Hill, Arthur E.; Pilkington, Richard D.

    2017-10-01

    This work explores the possibilities of using the pulsed direct current (dc) magnetron sputtering (PDCMS) process to deposit an alternative to the cadmium sulphide buffer layer in copper indium gallium diselenide - based solar cells. The main problems with the CdS layer are its toxic nature and its deposition using a chemical bath technique. These factors make it difficult to incorporate into in-line production and significant effort has been expended to find a suitable alternative buffer layer with in-line manufacturing capability. Towards this aim, the material properties of an In2S3 film, sputtered from a powder target, have been investigated. Films were deposited at different substrate temperatures ranging from ;no additional substrate heating; to 250 °C. The deposition of a single phase β-In2S3 without substrate heating/annealing has not previously been reported. The films deposited by the ion-enhanced PdcMS technique without any additional heating were found to be single phase. The grain size increased with increase in substrate temperature. However, this led to a decrease in the sulphur content; as a result the band gap decreased. For solar cell applications, the CdS buffer layer (optical band gap ∼2.4 eV) needs to be replaced with a material which has a band gap wider than 2.4 eV for improved performance and reduction of absorption loss in the blue wavelength region. Ideally the band gap should be between 2.6 and 3.0 eV. Our PdcMS room temperature deposited In2S3 had a measured band gap of 2.77 eV.

  6. ZnS-Passivated CdSe/CdS Co-sensitized Mesoporous Zn2SnO4 Based Solar Cells

    International Nuclear Information System (INIS)

    Kim, Kyungho; Park, Ji Eun; Park, Eun Su; Park, Yun Chang; Kim, Joosun; Im, Chan; Lee, Man-Jong

    2014-01-01

    Graphical abstract: - Highlights: • Mesoporous Zn 2 SnO 4 sensitized by CdSe/CdS QDs were synthesized via a two-step sequential process. • Assembled QDs were characterized by HRTEM and STEM mapping. • Efficiency increase in CdSe/CdS co-sensitized Zn 2 SnO 4 DSSCs is discussed. • The role of ZnS passivation layer is discussed by impedance spectroscopy. - Abstract: CdS and CdSe/CdS quantum dot (QD) sensitizers were assembled onto mesoporous ternary Zn 2 SnO 4 photoanodes using a two-step sequential process of successive ionic layer absorption and reaction (SILAR) and chemical bath deposition (CBD) for QD-cosensitized solar cell applications. The assembled CdS and CdSe QDs were observed using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), high-resolution TEM (HRTEM), and STEM/energy-dispersive X-ray spectroscopy (EDS) elemental mapping. CdSe/CdS cosensitized Zn 2 SnO 4 -based cells showed a higher absorption onset position, a stepwise band-edge level alignment, and, thereby, an improved power conversion efficiency (PCE) of 1.628% under one-sun conditions, which is the best result obtained using mesoporous Zn 2 SnO 4 reported to date. In addition, the effect of a ZnS passivation layer on the photovoltaic performance and aging behavior has been investigated. Electrochemical impedance spectroscopy (EIS) showed that the main role of the ZnS layer is to enhance the aging behavior of the CdSe/CdS/Zn 2 SnO 4 cells by improving the electron lifetime and charge recombination

  7. Room temperature fabrication of dielectric Bragg reflectors composed of a CaF2/ZnS multilayered coating.

    Science.gov (United States)

    Muallem, Merav; Palatnik, Alex; Nessim, Gilbert D; Tischler, Yaakov R

    2015-01-14

    We describe the design, fabrication, and characterization of mechanically stable, reproducible, and highly reflecting distributed Bragg reflectors (DBR) composed of thermally evaporated thin films of calcium fluoride (CaF2) and zinc sulfide (ZnS). CaF2 and ZnS were chosen as the low and high refractive index components of the multilayer DBR structures, with n = 1.43 and n = 2.38 respectively, because neither material requires substrate heating during the deposition process in order to produce optical quality thin films. DBRs consisting of seven pairs of CaF2 and ZnS layers, were fabricated with thicknesses of 96 and 58 nm, respectively, as characterized by high-resolution scanning electron microscopy (HR-SEM), and exhibited a center wavelength of λc = 550 nm and peak reflectance exceeding 99%. The layers showed good adhesion to each other and to the glass substrate, resulting in mechanically stable DBR coatings. Complete optical microcavities consisting of two such DBR coatings and a CaF2 spacer layer between them could be fabricated in a single deposition run. Optically, these structures exhibited a resonator quality factor of Q > 160. When a CaF2/ZnS DBR was grown, without heating the substrate during deposition, on top of a thin film containing the fluorescent dye Rhodamine 6G, the fluorescence intensity showed no degradation compared to an uncoated film, in contrast to a MgF2/ZnS DBR coating grown with substrate heating which showed a 92% reduction in signal. The ability to fabricate optical quality CaF2/ZnS DBRs without substrate heating, as introduced here, can therefore enable formation of low-loss high-reflectivity coatings on top of more delicate heat-sensitive materials such as organics and other nanostructured emitters, and hence facilitate the development of nanoemitter-based microcavity device applications.

  8. Traditionally produced sauerkraut as source of autochthonous functional starter cultures.

    Science.gov (United States)

    Beganović, Jasna; Kos, Blaženka; Leboš Pavunc, Andreja; Uroić, Ksenija; Jokić, Mladen; Šušković, Jagoda

    2014-01-01

    Spontaneous sauerkraut fermentation was performed at industrial scale in "Prehrana Inc.", Varaždin, in order to select autochthonous lactic acid bacteria (LAB) which were evaluated according probiotic criteria and tested for their capacity as probiotic starter cultures. At the end of the spontaneous sauerkraut fermentation, total LAB counts reached 9.0×10(5) CFU/ml. This underlines that the need for addition of the well characterised probiotic cultures, in appropriate viable cell counts, would be valuable in probiotic sauerkraut production. Phenotypic characterisation through API 50 CHL and SDS-PAGE of cell protein patterns revealed that Lactobacillus plantarum is predominant LAB strain in homofermentative phase of fermentation. Autochthonous LAB isolates SF1, SF2, SF4, SF9 and SF15 were selected based on the survival in in vitro gastrointestinal tract conditions. RAPD fingerprints indicated that the selected autochthonous LAB were distinct from one another. All of the strains efficiently inhibited the growth of indicator strains and satisfied technological properties such as acidification rate, tolerance to NaCl and viability during freeze-drying. Strains Lb. paraplantarum SF9 and Lb. brevis SF15, identified by AFLP DNA fingerprints, have shown the best properties to be applied as probiotic starter cultures, because of their highest adhesion to Caco-2 cells and expression of specific, protective S-layer proteins of 45 kDa in size. With addition of these strains, probiotic attribute of the sauerkraut will be achieved, including health promoting, nutritional, technological and economic advantages in large scale industrial sauerkraut production. Copyright © 2013 Elsevier GmbH. All rights reserved.

  9. Imaging of lactic acid bacteria with AFM-elasticity and adhesion maps and their relationship to biological and structural data

    Energy Technology Data Exchange (ETDEWEB)

    Schaer-Zammaretti, Prisca; Ubbink, Job

    2003-10-15

    The adhesion of lactic acid bacteria to the intestinal epithelium is one of the most important factors determining probiotic ability of a bacterial strain. Studying bacterial adhesion requires knowledge of the structure and properties of the bacterial surface, which can be studied by atomic force microscopy under native conditions. The observation of the surface topography of bacteria from the species Lactobacillus crispatus, L. helveticus and L. johnsonii shows major differences between bacteria having a crystalline-like protein layer as part of the cell wall and those without such layers. Force volume images calculated into elasticity and adhesion force maps of different bacterial strains show that L. crispatus and L. helveticus have a surface with a homogeneous stiffness with no adhesion events. This is most likely caused by the S-layer, which completely covers the surface of the bacteria. We infer that the absence of adhesion peaks is caused by the semi-crystalline character of such protein layers, in agreement with the results obtained from electron microscopy. Analysis of a number of L. johnsonii strains shows that these bacteria have surface properties which strongly differ from the L. crispatus and L. helveticus strains. For L. johnsonii DMS20533 and L. johnsonii ATCC33200 high adhesion forces are observed, which can be related to a surface rich in polysaccharides. L. johnsonii ATCC332 has lower adhesion forces compared to the other two and, furthermore, the surface topography shows depressions. We suppose that this strain has a surface pattern consisting of crystalline-like proteins alternating with polysaccharide-rich domains. The wide variety in surface properties of lactobacilli could well have wide-ranging implications for food processing and for health benefits.

  10. A High Molecular-Mass Anoxybacillus sp. SK3-4 Amylopullulanase: Characterization and Its Relationship in Carbohydrate Utilization

    Directory of Open Access Journals (Sweden)

    Kian Mau Goh

    2013-05-01

    Full Text Available An amylopullulanase of the thermophilic Anoxybacillus sp. SK3-4 (ApuASK was purified to homogeneity and characterized. Though amylopullulanases larger than 200 kDa are rare, the molecular mass of purified ApuASK appears to be approximately 225 kDa, on both SDS-PAGE analyses and native-PAGE analyses. ApuASK was stable between pH 6.0 and pH 8.0 and exhibited optimal activity at pH 7.5. The optimal temperature for ApuASK enzyme activity was 60 °C, and it retained 54% of its total activity for 240 min at 65 °C. ApuASK reacts with pullulan, starch, glycogen, and dextrin, yielding glucose, maltose, and maltotriose. Interestingly, most of the previously described amylopullulanases are unable to produce glucose and maltose from these substrates. Thus, ApuASK is a novel, high molecular-mass amylopullulanase able to produce glucose, maltose, and maltotriose from pullulan and starch. Based on whole genome sequencing data, ApuASK appeared to be the largest protein present in Anoxybacillus sp. SK3-4. The α-amylase catalytic domain present in all of the amylase superfamily members is present in ApuASK, located between the cyclodextrin (CD-pullulan-degrading N-terminus and the α-amylase catalytic C-terminus (amyC domains. In addition, the existence of a S-layer homology (SLH domain indicates that ApuASK might function as a cell-anchoring enzyme and be important for carbohydrate utilization in a streaming hot spring.

  11. Dry etched SiO2 Mask for HgCdTe Etching Process

    Science.gov (United States)

    Chen, Y. Y.; Ye, Z. H.; Sun, C. H.; Deng, L. G.; Zhang, S.; Xing, W.; Hu, X. N.; Ding, R. J.; He, L.

    2016-09-01

    A highly anisotropic etching process with low etch-induced damage is indispensable for advanced HgCdTe (MCT) infrared focal plane array (IRFPA) detectors. The inductively coupled plasma (ICP) enhanced reactive ion etching technique has been widely adopted in manufacturing HgCdTe IRFPA devices. An accurately patterned mask with sharp edges is decisive to accomplish pattern duplication. It has been reported by our group that the SiO2 mask functions well in etching HgCdTe with high selectivity. However, the wet process in defining the SiO2 mask is limited by ambiguous edges and nonuniform patterns. In this report, we patterned SiO2 with a mature ICP etching technique, prior to which a thin ZnS film was deposited by thermal evaporation. The SiO2 film etching can be terminated at the auto-stopping point of the ZnS layer thanks to the high selectivity of SiO2/ZnS in SF6 based etchant. Consequently, MCT etching was directly performed without any other treatment. This mask showed acceptable profile due to the maturity of the SiO2 etching process. The well-defined SiO2 pattern and the etched smooth surfaces were investigated with scanning electron microscopy and atomic force microscope. This new mask process could transfer the patterns exactly with very small etch-bias. A cavity with aspect-ratio (AR) of 1.2 and root mean square roughness of 1.77 nm was achieved first, slightly higher AR of 1.67 was also get with better mask profile. This masking process ensures good uniformity and surely benefits the delineation of shrinking pixels with its high resolution.

  12. Comparative Genomics of Campylobacter iguaniorum to Unravel Genetic Regions Associated with Reptilian Hosts.

    Science.gov (United States)

    Gilbert, Maarten J; Miller, William G; Yee, Emma; Kik, Marja; Zomer, Aldert L; Wagenaar, Jaap A; Duim, Birgitta

    2016-10-05

    Campylobacter iguaniorum is most closely related to the species C fetus, C hyointestinalis, and C lanienae Reptiles, chelonians and lizards in particular, appear to be a primary reservoir of this Campylobacter species. Here we report the genome comparison of C iguaniorum strain 1485E, isolated from a bearded dragon (Pogona vitticeps), and strain 2463D, isolated from a green iguana (Iguana iguana), with the genomes of closely related taxa, in particular with reptile-associated C fetus subsp. testudinum In contrast to C fetus, C iguaniorum is lacking an S-layer encoding region. Furthermore, a defined lipooligosaccharide biosynthesis locus, encoding multiple glycosyltransferases and bounded by waa genes, is absent from C iguaniorum Instead, multiple predicted glycosylation regions were identified in C iguaniorum One of these regions is > 50 kb with deviant G + C content, suggesting acquisition via lateral transfer. These similar, but non-homologous glycosylation regions were located at the same position on the genome in both strains. Multiple genes encoding respiratory enzymes not identified to date within the C. fetus clade were present. C iguaniorum shared highest homology with C hyointestinalis and C fetus. As in reptile-associated C fetus subsp. testudinum, a putative tricarballylate catabolism locus was identified. However, despite colonizing a shared host, no recent recombination between both taxa was detected. This genomic study provides a better understanding of host adaptation, virulence, phylogeny, and evolution of C iguaniorum and related Campylobacter taxa. © The Author 2016. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

  13. Cellular localization of D-lactate dehydrogenase and NADH oxidase from Archaeoglobus fulgidus.

    Science.gov (United States)

    Pagala, Vishwajeeth Reddy; Park, Joohye; Reed, David W; Hartzell, Patricia L

    2002-09-01

    Members of the genus Archaeoglobus are hyperthermophilic sulfate reducers with an optimal growth temperature of 83 degrees C. Archaeoglobus fulgidus can utilize simple compounds including D-lactate, L-lactate and pyruvate as the sole substrate for carbon and electrons for dissimilatory sulfate reduction. Previously we showed that this organism makes a D-lactate dehydrogenase (Dld) that requires FAD and Zn2+ for activity. To determine the cellular location and topology of Dld and to identify proteins that interact with Dld, an antibody directed against Dld was prepared. Immunocytochemical studies using gold particle-coated secondary antibodies show that more than 85% of Dld is associated with the membrane. A truncated form of Dld was detected in immunoblots of whole cells treated with protease, showing that Dld is an integral membrane protein and that a significant portion of Dld, including part of the FAD-binding pocket, is outside the membrane facing the S-layer. The gene encoding Dld is part of an operon that includes noxA2, which encodes one of several NADH oxidases in A. fulgidus. Previous studies have shown that NoxA2 remains bound to Dld during purification. Thin sections of A. fulgidus probed simultaneously with antibodies against Dld and NoxA2 show that both proteins co-localized to the same sites in the membrane. Although these data show a tight interaction between NoxA2 and Dld, the role of NoxA2 in electron transport reactions is unknown. Rather, NoxA2 may protect proteins involved in electron transfer by reducing O2 to H2O2 or H2O.

  14. Cooperative degradation of chitin by extracellular and cell surface-expressed chitinases from Paenibacillus sp. strain FPU-7.

    Science.gov (United States)

    Itoh, Takafumi; Hibi, Takao; Fujii, Yutaka; Sugimoto, Ikumi; Fujiwara, Akihiro; Suzuki, Fumiko; Iwasaki, Yukimoto; Kim, Jin-Kyung; Taketo, Akira; Kimoto, Hisashi

    2013-12-01

    Chitin, a major component of fungal cell walls and invertebrate cuticles, is an exceedingly abundant polysaccharide, ranking next to cellulose. Industrial demand for chitin and its degradation products as raw materials for fine chemical products is increasing. A bacterium with high chitin-decomposing activity, Paenibacillus sp. strain FPU-7, was isolated from soil by using a screening medium containing α-chitin powder. Although FPU-7 secreted several extracellular chitinases and thoroughly digested the powder, the extracellular fluid alone broke them down incompletely. Based on expression cloning and phylogenetic analysis, at least seven family 18 chitinase genes were found in the FPU-7 genome. Interestingly, the product of only one gene (chiW) was identified as possessing three S-layer homology (SLH) domains and two glycosyl hydrolase family 18 catalytic domains. Since SLH domains are known to function as anchors to the Gram-positive bacterial cell surface, ChiW was suggested to be a novel multimodular surface-expressed enzyme and to play an important role in the complete degradation of chitin. Indeed, the ChiW protein was localized on the cell surface. Each of the seven chitinase genes (chiA to chiF and chiW) was cloned and expressed in Escherichia coli cells for biochemical characterization of their products. In particular, ChiE and ChiW showed high activity for insoluble chitin. The high chitinolytic activity of strain FPU-7 and the chitinases may be useful for environmentally friendly processing of chitin in the manufacture of food and/or medicine.

  15. Transduction-like gene transfer in the methanogen Methanococcus voltae

    Science.gov (United States)

    Bertani, G.

    1999-01-01

    Strain PS of Methanococcus voltae (a methanogenic, anaerobic archaebacterium) was shown to generate spontaneously 4.4-kbp chromosomal DNA fragments that are fully protected from DNase and that, upon contact with a cell, transform it genetically. This activity, here called VTA (voltae transfer agent), affects all markers tested: three different auxotrophies (histidine, purine, and cobalamin) and resistance to BES (2-bromoethanesulfonate, an inhibitor of methanogenesis). VTA was most effectively prepared by culture filtration. This process disrupted a fraction of the M. voltae cells (which have only an S-layer covering their cytoplasmic membrane). VTA was rapidly inactivated upon storage. VTA particles were present in cultures at concentrations of approximately two per cell. Gene transfer activity varied from a minimum of 2 x 10(-5) (BES resistance) to a maximum of 10(-3) (histidine independence) per donor cell. Very little VTA was found free in culture supernatants. The phenomenon is functionally similar to generalized transduction, but there is no evidence, for the time being, of intrinsically viral (i.e., containing a complete viral genome) particles. Consideration of VTA DNA size makes the existence of such viral particles unlikely. If they exist, they must be relatively few in number;perhaps they differ from VTA particles in size and other properties and thus escaped detection. Digestion of VTA DNA with the AluI restriction enzyme suggests that it is a random sample of the bacterial DNA, except for a 0.9-kbp sequence which is amplified relative to the rest of the bacterial chromosome. A VTA-sized DNA fraction was demonstrated in a few other isolates of M. voltae.

  16. Ultrastructural and three-dimensional study of post-LASIK ectasia cornea.

    Science.gov (United States)

    Akhtar, Saeed; Alkatan, Hind; Kirat, Omar; Almubrad, Turki

    2014-01-01

    Post-laser in situ keratomileusis (LASIK) corneal ectasia is a serious late postoperative complication. Here, we report the ultrastructural features of the post-LASIK cornea of two patients. Two normal corneas (age 24 and 37 years old) and two post-LASIK ectaic corneas from two patients (A and B) were studied. The "patient A" (age 27 years) underwent penetrating keratoplasty and "patient B" (age 31 years) underwent deep-anterior lamellar keratoplasty. The excised corneas were processed for light and electron microscopy. A total of 120 images for three-dimensional (3D) reconstruction were taken by using the software "Recorder" and using a bottom mounted camera "Quemesa" attached to a JOEL 1400 transmission electron microscope. The 3D images were constructed using "Visual Kai" software. In the post-LASIK cornea, the hemidesmosomes, the basement membrane, and Bowman"s layer were abnormal. The stromal lamellae were thin and disorganized. The collagen fibrils (CFs) diameter and interfibrillar spacing had decreased. Aggregated microfibrils were present in the Bowman's layer and all parts of the stroma. A large number of microfilaments were present at the detachment end of the flap and residual stroma. The 3D images showed the presence of collagen microfibrils and proteoglycans (PGs) within the CF of the normal and post-LASIK cornea. The collagen microfibrils and PGs within the CFs had degenerated in the post-LASIK cornea. Collagen microfibrils and PGs within the CFs were degenerated, leading to the degeneration of CFs, followed by the disorganization of lamellae in post-LASIK cornea. The CFs diameter and interfibrillar spacing decreased. Copyright © 2013 Wiley Periodicals, Inc.

  17. Bi-sulphotellurides associated with Pb - Bi - (Sb ± Ag, Cu, Fe) sulphosalts: an example from the Stan Terg deposit in Kosovo

    Science.gov (United States)

    Kołodziejczyk, Joanna; Pršek, Jaroslav; Voudouris, Panagiotis Ch.; Melfos, Vasilios

    2017-08-01

    New mineralogical and mineral-chemical data from the Stan Terg deposit, Kosovo, revealed the presence of abundant Bi-sulphotellurides associated with Bi- and Sb-sulphosalts and galena in pyrite-pyrrhotite-rich skarn-free ore bodies (ores without skarn minerals). The Bi-bearing association comprises Bi-sulphotellurides (joséite-A, joséite-B, unnamed phase A with a chemical formula close to (Bi,Pb)2(TeS)2, unnamed phase B with a chemical composition close to (Bi,Pb)2.5Te1.5S1.5), ikunolite, cosalite, Sb-lillianite, members of the kobellite series and Bi-jamesonite. Compositional trends of the Bi-sulphotellurides suggest lattice-scale incorporation of Bi-(Pb)-rich module and/or admixture with submicroscopic PbS layers in modulated structures, or complicated Bi-Te substitution. Cosalite is characterized by high Sb (max. 3.94 apfu), and low Cu and Ag (up to 0.72 apfu of Cu+Ag). Jamesonite from this mineralization has elevated Bi content, from 0.85 to 2.30 apfu. The negligible content of Au and Ag in the Bi-sulphotellurides, the low content of Ag in Bi-sulphosalts, together with the lack of Au-Ag bearing phases in the mineralization, indicate either ore deposition from fluid(s) depleted in precious metals, or physico-chemical conditions of ore formation preventing Au and Ag precipitation at the deposit site. The temperature of initial mineralization may have exceeded 400 °C as suggested by the lamellar exsolution textures observed in lillianite, which indicate breakdown textures from decomposition of high-temperature initial crystals. Non-stoichiometric phases among the Bi-sulphosalts and sulphotellurides studied at Stan Terg reflect modulated growth processes in a metasomatic environment.

  18. CdCl{sub 2} treatment related diffusion phenomena in Cd{sub 1−x}Zn{sub x}S/CdTe solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Kartopu, G., E-mail: giray.kartopu@glyndwr.ac.uk; Clayton, A. J.; Barrioz, V.; Lamb, D. A.; Irvine, S. J. C. [Centre for Solar Energy Research (CSER), Glyndŵr University, OpTIC, St. Asaph Business Park, St. Asaph LL17 0JD (United Kingdom); Taylor, A. A. [Physics Department, Durham University, Durham DH1 3LE (United Kingdom)

    2014-03-14

    Utilisation of wide bandgap Cd{sub 1−x}Zn{sub x}S alloys as an alternative to the CdS window layer is an attractive route to enhance the performance of CdTe thin film solar cells. For successful implementation, however, it is vital to control the composition and properties of Cd{sub 1−x}Zn{sub x}S through device fabrication processes involving the relatively high-temperature CdTe deposition and CdCl{sub 2} activation steps. In this study, cross-sectional scanning transmission electron microscopy and depth profiling methods were employed to investigate chemical and structural changes in CdTe/Cd{sub 1−x}Zn{sub x}S/CdS superstrate device structures deposited on an ITO/boro-aluminosilicate substrate. Comparison of three devices in different states of completion—fully processed (CdCl{sub 2} activated), annealed only (without CdCl{sub 2} activation), and a control (without CdCl{sub 2} activation or anneal)—revealed cation diffusion phenomena within the window layer, their effects closely coupled to the CdCl{sub 2} treatment. As a result, the initial Cd{sub 1−x}Zn{sub x}S/CdS bilayer structure was observed to unify into a single Cd{sub 1−x}Zn{sub x}S layer with an increased Cd/Zn atomic ratio; these changes defining the properties and performance of the Cd{sub 1−x}Zn{sub x}S/CdTe device.

  19. Development of Earth-Abundant and Non-Toxic Thin-Film Solar Cells

    Science.gov (United States)

    Park, Helen Hejin

    Although solar energy is the most abundant energy resource available, photovoltaic solar cells must consist of sufficiently abundant and environmentally friendly elements, for scalable low-cost production to provide a major amount of the world's energy supply. However, scalability is limited in current thin-film solar cell technologies based on Cu(In,Ga)(S,Se)2 and CdTe due to scarce, expensive, and toxic elements. Thin-film solar cells consisting of earth-abundant and non-toxic materials were made from pulsed chemical vapor deposition (pulsed-CVD) of SnS as the p-type absorber layer and atomic layer deposition (ALD) of Zn(O,S) as the n-type buffer layer. Solar cells with a structure of Mo/SnS/Zn(O,S)/ZnO/ITO were studied by varying the synthesis conditions of the SnS and Zn(O,S) layers. Annealing SnS in hydrogen sulfide increased the mobility by more than one order of magnitude, and improved the power conversion efficiency of the solar cell devices. Solar cell performance can be further optimized by adjusting the stoichiometry of Zn(O,S), and by tuning the electrical properties of Zn(O,S) through various in situ or post-annealing treatments. Zn(O,S) can be post-annealed in oxygen atmosphere or doped with nitrogen, by ammonium hydroxide or ammonia gas, during the ALD growth to reduce the carrier concentration, which can be critical for reducing interface recombination at the p-n junction. High carrier concentration buffer layers can be critical for reducing contact resistance with the ITO layer. Zn(O,S) can also be incorporated with aluminum by trimethylaluminum (TMA) doses to either increase or decrease the carrier concentration based on the stoichiometry of Zn(O,S).

  20. Genetic transformation of novel isolates of chicken Lactobacillus bearing probiotic features for expression of heterologous proteins: a tool to develop live oral vaccines

    Directory of Open Access Journals (Sweden)

    Neumann Elisabeth

    2006-01-01

    Full Text Available Abstract Background The use of lactic acid bacteria as vehicles to delivery antigens to immunize animals is a promising issue. When genetically modified, these bacteria can induce a specific local and systemic immune response against selected pathogens. Gastric acid and bile salts tolerance, production of antagonistic substances against pathogenic microorganisms, and adhesive ability to gut epithelium are other important characteristics that make these bacteria useful for oral immunization. Results Bacteria isolated on de Man, Rogosa and Sharpe medium (MRS from different gastrointestinal portions of broiler chicks were evaluated for their resistance to artificial gastric acid and bile salts, production of hydrogen peroxide, and cell surface hydrophobicity. Thirty-eight isolates were first typed at species level by PCR amplification of 16S-23S rRNA intergenic spacers using universal primers that anneal within 16S and 23S genes, followed by restriction digestion analyses of PCR amplicons (PCR-ARDRA. An expression cassette was assembled onto the pCR2.1-Topo vector by cloning the promoter, leader peptide, cell wall anchor and terminator sequences derived from the laminin binding S-layer protein gene of L. crispatus strain F5.7 (lbs gene. A sequence encoding the green fluorescent protein (GFP was inserted as reporter gene, and an erythromycin resistance gene was added as selective marker. All constructs were able to express GFP in the cloning host E. coli XL1-Blue and different Lactobacillus strains as verified by FACS and laser scanning confocal microscopy. Conclusion Lactobacillus isolated from gastrointestinal tract of broiler chickens and selected for probiotic characteristics can be genetically modified by introducing an expression cassette into the lbs locus. The transformed bacteria expressed on its cell wall surface different fluorescent proteins used as reporters of promoter function. It is possible then that similar bacterial model

  1. Mining Proteomic Data to Expose Protein Modifications in Methanosarcina mazei strain Gö1

    Directory of Open Access Journals (Sweden)

    Deborah eLeon

    2015-03-01

    Full Text Available Proteomic tools identify constituents of complex mixtures, often delivering long lists of identified proteins. The high-throughput methods excel at matching tandem mass spectrometry data to spectra predicted from sequence databases. Unassigned mass spectra are ignored, but could, in principle, provide valuable information on unanticipated modifications and improve protein annotations while consuming limited quantities of material. Strategies to mine information from these discards are presented, along with discussion of features that, when present, provide strong support for modifications. In this study we mined LC-MS/MS datasets of proteolytically-digested concanavalin A pull down fractions from Methanosarcina mazei Gö1 cell lysates. Analyses identified 154 proteins. Many of the observed proteins displayed post-translationally modified forms, including O-formylated and methyl-esterified segments that appear biologically relevant (i.e., not artifacts of sample handling. Interesting cleavages and modifications (e.g., S-cyanylation and trimethylation were observed near catalytic sites of methanogenesis enzymes. Of 31 Methanosarcina protein N-termini recovered by concanavalin A binding or from a previous study, only M. mazei S-layer protein MM1976 and its M. acetivorans C2A orthologue, MA0829, underwent signal peptide excision. Experimental results contrast with predictions from algorithms SignalP 3.0 and Exprot, which were found to over-predict the presence of signal peptides. Proteins MM0002, MM0716, MM1364, and MM1976 were found to be glycosylated, and employing chromatography tailored specifically for glycopeptides will likely reveal more.This study supplements limited, existing experimental datasets of mature archaeal N-termini, including presence or absence of signal peptides, translation initiation sites, and other processing. Methanosarcina surface and membrane proteins are richly modified.

  2. Structural and chemical transformations in SnS thin films used in chemically deposited photovoltaic cells

    International Nuclear Information System (INIS)

    Avellaneda, David; Delgado, Guadalupe; Nair, M.T.S.; Nair, P.K.

    2007-01-01

    Chemically deposited SnS thin films possess p-type electrical conductivity. We report a photovoltaic structure: SnO 2 :F-CdS-SnS-(CuS)-silver print, with V oc > 300 mV and J sc up to 5 mA/cm 2 under 850 W/m 2 tungsten halogen illumination. Here, SnO 2 :F is a commercial spray-CVD (Pilkington TEC-8) coating, and the rest deposited from different chemical baths: CdS (80 nm) at 333 K, SnS (450 nm) and CuS (80 nm) at 293-303 K. The structure may be heated in nitrogen at 573 K, before applying the silver print. The photovoltaic behavior of the structure varies with heating: V oc ∼ 400 mV and J sc 2 , when heated at 423 K in air, but V oc decreases and J sc increases when heated at higher temperatures. These photovoltaic structures have been found to be stable over a period extending over one year by now. The overall cost of materials, simplicity of the deposition process, and possibility of easily varying the parameters to improve the cell characteristics inspire further work. Here we report two different baths for the deposition of SnS thin films of about 500 nm by chemical deposition. There is a considerable difference in the nature of growth, crystalline structure and chemical stability of these films under air-heating at 623-823 K or while heating SnS-CuS layers, evidenced in XRF and grazing incidence angle XRD studies. Heating of SnS-CuS films results in the formation of SnS-Cu x SnS y . 'All-chemically deposited photovoltaic structures' involving these materials are presented

  3. Complementation of an aglB Mutant of Methanococcus maripaludis with Heterologous Oligosaccharyltransferases.

    Directory of Open Access Journals (Sweden)

    Yan Ding

    Full Text Available The oligosaccharyltransferase is the signature enzyme for N-linked glycosylation in all domains of life. In Archaea, this enzyme termed AglB, is responsible for transferring lipid carrier-linked glycans to select asparagine residues in a variety of target proteins including archaellins, S-layer proteins and pilins. This study investigated the ability of a variety of AglBs to compensate for the oligosaccharyltransferase activity in Methanococcus maripaludis deleted for aglB, using archaellin FlaB2 as the reporter protein since all archaellins in Mc. maripaludis are modified at multiple sites by an N-linked tetrasaccharide and this modification is required for archaellation. In the Mc. maripaludis ΔaglB strain FlaB2 runs as at a smaller apparent molecular weight in western blots and is nonarchaellated. We demonstrate that AglBs from Methanococcus voltae and Methanothermococcus thermolithotrophicus functionally replaced the oligosaccharyltransferase activity missing in the Mc. maripaludis ΔaglB strain, both returning the apparent molecular weight of FlaB2 to wildtype size and restoring archaellation. This demonstrates that AglB from Mc. voltae has a relaxed specificity for the linking sugar of the transferred glycan since while the N-linked glycan present in Mc. voltae is similar to that of Mc. maripaludis, the Mc. voltae glycan uses N-acetylglucosamine as the linking sugar. In Mc. maripaludis that role is held by N-acetylgalactosamine. This study also identifies aglB from Mtc. thermolithotrophicus for the first time by its activity. Attempts to use AglB from Methanocaldococcus jannaschii, Haloferax volcanii or Sulfolobus acidocaldarius to functionally replace the oligosaccharyltransferase activity missing in the Mc. maripaludis ΔaglB strain were unsuccessful.

  4. Complementation of an aglB Mutant of Methanococcus maripaludis with Heterologous Oligosaccharyltransferases.

    Science.gov (United States)

    Ding, Yan; Vrionis, Helen A; Schneider, James; Berezuk, Alison; Khursigara, Cezar M; Jarrell, Ken F

    2016-01-01

    The oligosaccharyltransferase is the signature enzyme for N-linked glycosylation in all domains of life. In Archaea, this enzyme termed AglB, is responsible for transferring lipid carrier-linked glycans to select asparagine residues in a variety of target proteins including archaellins, S-layer proteins and pilins. This study investigated the ability of a variety of AglBs to compensate for the oligosaccharyltransferase activity in Methanococcus maripaludis deleted for aglB, using archaellin FlaB2 as the reporter protein since all archaellins in Mc. maripaludis are modified at multiple sites by an N-linked tetrasaccharide and this modification is required for archaellation. In the Mc. maripaludis ΔaglB strain FlaB2 runs as at a smaller apparent molecular weight in western blots and is nonarchaellated. We demonstrate that AglBs from Methanococcus voltae and Methanothermococcus thermolithotrophicus functionally replaced the oligosaccharyltransferase activity missing in the Mc. maripaludis ΔaglB strain, both returning the apparent molecular weight of FlaB2 to wildtype size and restoring archaellation. This demonstrates that AglB from Mc. voltae has a relaxed specificity for the linking sugar of the transferred glycan since while the N-linked glycan present in Mc. voltae is similar to that of Mc. maripaludis, the Mc. voltae glycan uses N-acetylglucosamine as the linking sugar. In Mc. maripaludis that role is held by N-acetylgalactosamine. This study also identifies aglB from Mtc. thermolithotrophicus for the first time by its activity. Attempts to use AglB from Methanocaldococcus jannaschii, Haloferax volcanii or Sulfolobus acidocaldarius to functionally replace the oligosaccharyltransferase activity missing in the Mc. maripaludis ΔaglB strain were unsuccessful.

  5. The characteristics exosporium antigens from different vaccine strains of bacillus antracis

    International Nuclear Information System (INIS)

    Baranova, E.; Biketov, S.; Dunaytsev, I.; Mironova, R.; Dyatlov, I.

    2009-01-01

    To develop of both test-systems for rapid detection and identification of B. anthracis spores and a new subunit vaccine the antigens on the spore surface should be characterized. Exosporium consists of two layers-basal and peripheral and has been form by protein, amino- and neutral polysaccharides, lipids and ash. Number of anthrax exosporium proteins was described and identified: glycoprotein BclA, BclB, alanine racemase, inosine hydrolase, glycosyl hydrolase, superoxid dismutase, ExsF, ExsY, ExsK,CotB,CotY and SoaA. So far no glycosylated proteins other then highly immunogenic glycoproteins BclA, BclB were detected in the B. anthracis spore extract although several exosporium-specific glycoprotein have been described in other members of the B.cereus family- B. thuringiensis and B. cereus. Although EA1 protein originally described as main component of S-layer from vegetative cells he can regular observed in different exosporium preparations and additionally some anti- EA1 monoclonal antibodies able to recognize spore surface. We have revealed that EA1 isolated from spore of Russians strain STI-1contain carbohydrate which determine immunogenicity of this antigen. Because some time ago we have found that exosporium protein's pattern variable among B. anthracis strains we investigated exosporium from spore of different strains of B. anthracis including STI-1, Ames, Stern and others. We have comparative characterized antigens by using Western Blotting, Two-Dimensional electrophoresis and Mass Spec analysis. The results of analysis will be presented and discussed.(author)

  6. Mercury’s gravity field, tidal Love number k2, and spin axis orientation revealed with MESSENGER radio tracking data

    Science.gov (United States)

    Verma, Ashok Kumar; Margot, Jean-Luc

    2015-11-01

    We are conducting an independent analysis of two-way Doppler and two-way range radio tracking data from the MESSENGER spacecraft in orbit around Mercury from 2011 to 2015. Our goals are to estimate Mercury’s gravity field and to obtain independent estimates of the tidal Love number k2 and spin axis orientation. Our gravity field solution reproduces existing values with high fidelity, and prospects for recovery of the other quantities are excellent.The tidal Love number k2 provides powerful constraints on interior models of Mercury, including the mechanical properties of the mantle and the possibility of a solid FeS layer at the top of the core. Current gravity analyses cannot rule out a wide range of values (k2=43-0.50) and a variety of plausible interior models. We are seeking an independent estimate of tidal Love number k2 with improved errors to further constrain these models.Existing gravity-based solutions for Mercury's spin axis orientation differ from those of Earth-based radar and topography-based solutions. This difference may indicate an error in one of the determinations, or a real difference between the orientations about which the gravity field and the crust rotate, which can exist in a variety of plausible configuration. Securing an independent estimate of the spin axis orientation is vital because this quantity has a profound impact on the determination of the moment of inertia and interior models.We have derived a spherical harmonic solution of the gravity field to degree and order 40 as well as estimates of the tidal Love number k2 and spin axis orientation

  7. Mercury's gravity field, tidal Love number k2, and spin axis orientation revealed with MESSENGER radio tracking data

    Science.gov (United States)

    Verma, A. K.; Margot, J. L.

    2015-12-01

    We are conducting an independent analysis of two-way Doppler and two-way range radio tracking data from the MESSENGER spacecraft in orbit around Mercury from 2011 to 2015. Our goals are to estimate Mercury's gravity field and to obtain independent estimates of the tidal Love number k2 and spin axis orientation. Our gravity field solution reproduces existing values with high fidelity, and prospects for recovery of the other quantities are excellent. The tidal Love number k2 provides powerful constraints on interior models of Mercury, including the mechanical properties of the mantle and the possibility of a solid FeS layer at the top of the core. Current gravity analyses cannot rule out a wide range of values (k2=43-0.50) and a variety of plausible interior models. We are seeking an independent estimate of tidal Love number k2 with improved errors to further constrain these models. Existing gravity-based solutions for Mercury's spin axis orientation differ from those of Earth-based radar and topography-based solutions. This difference may indicate an error in one of the determinations, or a real difference between the orientations about which the gravity field and the crust rotate, which can exist in a variety of plausible configuration. Securing an independent estimate of the spin axis orientation is vital because this quantity has a profound impact on the determination of the moment of inertia and interior models. We have derived a spherical harmonic solution of the gravity field to degree and order 40 as well as estimates of the tidal Love number k2 and spin axis orientation.

  8. Evaluation of corrosion products formed by sulfidation as inhibitors of the naphthenic corrosion of AISI-316 steel

    Science.gov (United States)

    Sanabria-Cala, J. A.; Montañez, N. D.; Laverde Cataño, D.; Y Peña Ballesteros, D.; Mejía, C. A.

    2017-12-01

    Naphthenic acids present in oil from most regions worldwide currently stand as the main responsible for the naphthenic corrosion problems, affecting the oil-refining industry. The phenomenon of sulfidation, accompanying corrosion processes brought about by naphthenic acids in high-temperature refining plant applications, takes place when the combination of sulfidic acid (H2S) with Fe forms layers of iron sulphide (FeS) on the material surface, layers with the potential to protect the material from attack by other corrosive species like naphthenic acids. This work assessed corrosion products formed by sulfidation as inhibitors of naphthenic corrosion rate in AISI-316 steel exposed to processing conditions of simulated crude oil in a dynamic autoclave. Calculation of the sulfidation and naphthenic corrosion rates were determined by gravimetry. The surfaces of the AISI-316 gravimetric coupons exposed to acid systems; were characterized morphologically by X-Ray Diffraction (XRD) and X-ray Fluorescence by Energy Dispersive Spectroscopy (EDS) combined with Scanning Electron Microscopy (SEM). One of the results obtained was the determination of an inhibiting effect of corrosion products at 250 and 300°C, where lower corrosion rate levels were detected. For the temperature of 350°C, naphthenic corrosion rates increased due to deposition of naphthenic acids on the areas where corrosion products formed by sulfidation have lower homogeneity and stability on the surface, thus accelerating the destruction of AISI-316 steel. The above provides an initial contribution to oil industry in search of new alternatives to corrosion control by the attack of naphthenic acids, from the formation of FeS layers on exposed materials in the processing of heavy crude oils with high sulphur content.

  9. Choroidal vasculature characteristics based choroid segmentation for enhanced depth imaging optical coherence tomography images

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qiang; Niu, Sijie [School of Computer Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Yuan, Songtao; Fan, Wen, E-mail: fanwen1029@163.com; Liu, Qinghuai [Department of Ophthalmology, The First Affiliated Hospital with Nanjing Medical University, Nanjing 210029 (China)

    2016-04-15

    Purpose: In clinical research, it is important to measure choroidal thickness when eyes are affected by various diseases. The main purpose is to automatically segment choroid for enhanced depth imaging optical coherence tomography (EDI-OCT) images with five B-scans averaging. Methods: The authors present an automated choroid segmentation method based on choroidal vasculature characteristics for EDI-OCT images with five B-scans averaging. By considering the large vascular of the Haller’s layer neighbor with the choroid-sclera junction (CSJ), the authors measured the intensity ascending distance and a maximum intensity image in the axial direction from a smoothed and normalized EDI-OCT image. Then, based on generated choroidal vessel image, the authors constructed the CSJ cost and constrain the CSJ search neighborhood. Finally, graph search with smooth constraints was utilized to obtain the CSJ boundary. Results: Experimental results with 49 images from 10 eyes in 8 normal persons and 270 images from 57 eyes in 44 patients with several stages of diabetic retinopathy and age-related macular degeneration demonstrate that the proposed method can accurately segment the choroid of EDI-OCT images with five B-scans averaging. The mean choroid thickness difference and overlap ratio between the authors’ proposed method and manual segmentation drawn by experts were −11.43 μm and 86.29%, respectively. Conclusions: Good performance was achieved for normal and pathologic eyes, which proves that the authors’ method is effective for the automated choroid segmentation of the EDI-OCT images with five B-scans averaging.

  10. Factors influencing degradation of trichloroethylene by sulfide-modified nanoscale zero-valent iron in aqueous solution.

    Science.gov (United States)

    Dong, Haoran; Zhang, Cong; Deng, Junmin; Jiang, Zhao; Zhang, Lihua; Cheng, Yujun; Hou, Kunjie; Tang, Lin; Zeng, Guangming

    2018-02-07

    Sulfide-modified nanoscale zero-valent iron (S/NZVI) has been considered as an efficient material to degrade trichloroethylene (TCE) in groundwater. However, some critical factors influencing the dechlorination of TCE by S/NZVI have not been investigated clearly. In this study, the effects of Fe/S molar ratio, initial pH, dissolved oxygen and particle aging on TCE dechlorination by S/NZVI (using dithionite as sulfidation reagent) were studied. Besides, the feasibility of reactivation of the aged-NZVI by sulfidation treatment was looked into. The results show that the Fe/S molar ratio and initial pH significantly influenced the TCE dechlorination, and a higher TCE dechlorination was observed at Fe/S molar ratio of ∼60 under alkaline condition. Spectroscopic analyses demonstrate that the enhanced TCE dechlorination was associated with the presence of FeS on the surface of S/NZVI. Dissolved oxygen had little effect on TCE dechlorination by S/NZVI, revealing that the FeS layer could be able to alleviate the surface passivation of NZVI caused by oxidation. Aging of S/NZVI up to 10-20 d only slightly decreased the dechlorination efficiency of TCE. Although an obvious drop in dechorination efficiency was observed for the S/NZVI aged for 30 d, it still exhibited a higher reactivity than the bare NZVI. This indicates that sulfidation of NZVI did prolong its lifetime. Additionally, sulfidation treatment was used to reactivate the aged NZVI, and the results show that the reactivated NZVI even had higher reactivity than the fresh NZVI, suggesting that sulfidation treatment would be a promising method to reactivate the aged NZVI. Copyright © 2018 Elsevier Ltd. All rights reserved.

  11. The influence of physical and technological magnetron sputtering modes on the structure and optical properties of CdS and CdTe films

    Directory of Open Access Journals (Sweden)

    G.S. Khrypunov

    2017-07-01

    Full Text Available To create technology for preparation of CdS and CdTe thin films by direct current magnetron sputtering, the influence of physical and technological condensation modes on the crystal structure and optical properties of these films were investigated. The laboratory method of DC magnetron sputtering with preheating of the target for the mentioned films on glass substrates was developed. We obtained the CdS layers with hexagonal structure 150…200 nm thick under conditions when the plasma discharge current density was 1.1 mA/cm2 and the deposition rate – 30…40 nm/min. The bandgap in the obtained CdS films is Eg = 2.38…2.41 eV. After annealing in vacuum, the optical transparence of CdS films reaches 80…90%, which allows to use these films as a transparent window layer in solar cells based on heterojunctions of CdS/CdTe. When the plasma discharge current density is 2.2…5.4 mA/cm2 and the deposition rate is 200 nm/min, we obtained CdTe layers with hexagonal structure up to 5 µm thick. The transmittance of CdTe films with hexagonal structure in the wavelength range of the visible spectrum is up to 5%, and in the infrared spectral range is about 60%. The bandgap in the obtained CdTe layers of different thickness is 1.52…1.54 eV. After chloride treatment as a result of the phase transition wurtzite–sphalerite, the investigated CdTe films contain only the stable cubic structure and can be used as a base layer of solar cells.

  12. Determination of anisotropic velocity model by reflection tomography of compression and shear modes; Determination de modele de vitesse anisotrope par tomographie de reflexion des modes de compression et de cisaillement

    Energy Technology Data Exchange (ETDEWEB)

    Stopin, A.

    2001-12-01

    As the jump from 2D to 3D, seismic exploration lives a new revolution with the use of converted PS waves. Indeed PS converted waves are proving their potential as a tool for imaging through gas; lithology discrimination; structural confirmation; and more. Nevertheless, processing converted shear data and in particular determining accurate P and S velocity models for depth imaging of these data is still a challenging problem, especially when the subsurface is anisotropic. To solve this velocity model determination problem we propose to use reflection travel time tomography. In a first step, we derive a new approximation of the exact phase velocity equation of the SV wave in anisotropic (TI) media. This new approximation is valid for non-weak anisotropy and is mathematically simpler to handle than the exact equation. Then, starting from an isotropic reflection tomography tool developed at Lt-'P, we extend the isotropic bending ray tracing method to the anisotropic case and we implement the quantities necessary for the determination of the anisotropy parameters from the travel time data. Using synthetic data we then study the influence of the different anisotropy parameters on the travel times. From this analysis we propose a methodology to determine a complete anisotropic subsurface model (P and S layer velocities, interface geometries, anisotropy parameters). Finally, on a real data set from the Gulf of Mexico we demonstrate that this new anisotropic reflection tomography tool allows us to obtain a reliable subsurface model yielding kinematically correct and mutually coherent PP and PS images in depth; such a result could not be obtained with an isotropic velocity model. Similar results are obtained on a North Sea data set. (author)

  13. A configurable distributed high-performance computing framework for satellite's TDI-CCD imaging simulation

    Science.gov (United States)

    Xue, Bo; Mao, Bingjing; Chen, Xiaomei; Ni, Guoqiang

    2010-11-01

    This paper renders a configurable distributed high performance computing(HPC) framework for TDI-CCD imaging simulation. It uses strategy pattern to adapt multi-algorithms. Thus, this framework help to decrease the simulation time with low expense. Imaging simulation for TDI-CCD mounted on satellite contains four processes: 1) atmosphere leads degradation, 2) optical system leads degradation, 3) electronic system of TDI-CCD leads degradation and re-sampling process, 4) data integration. Process 1) to 3) utilize diversity data-intensity algorithms such as FFT, convolution and LaGrange Interpol etc., which requires powerful CPU. Even uses Intel Xeon X5550 processor, regular series process method takes more than 30 hours for a simulation whose result image size is 1500 * 1462. With literature study, there isn't any mature distributing HPC framework in this field. Here we developed a distribute computing framework for TDI-CCD imaging simulation, which is based on WCF[1], uses Client/Server (C/S) layer and invokes the free CPU resources in LAN. The server pushes the process 1) to 3) tasks to those free computing capacity. Ultimately we rendered the HPC in low cost. In the computing experiment with 4 symmetric nodes and 1 server , this framework reduced about 74% simulation time. Adding more asymmetric nodes to the computing network, the time decreased namely. In conclusion, this framework could provide unlimited computation capacity in condition that the network and task management server are affordable. And this is the brand new HPC solution for TDI-CCD imaging simulation and similar applications.

  14. Electronic structure of Cu{sub 2}ZnSn(S{sub x}Se{sub 1-x}){sub 4} surface and CdS/Cu{sub 2}ZnSn(S{sub x}Se{sub 1-x}){sub 4} interface

    Energy Technology Data Exchange (ETDEWEB)

    Udaka, Yusuke; Takaki, Shin' ichi; Isowaki, Keisuke; Terada, Norio [Graduate School of Science and Engineering, Kagoshima University, 1-21-40 Korimoto, Kagoshima 890-0065 (Japan); Nagai, Takehiko; Kim, Kang Min; Kim, Shinho; Tampo, Hitoshi; Shibata, Hajime; Matsubara, Koji; Niki, Shigeru [Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Sakai, Noriyuki; Kato, Takuya; Sugimoto, Hiroki [Solar Frontier K.K., 123-1 Shimo-Kawairi, Atsugi 243-0206 (Japan)

    2017-06-15

    Changes of the electronic structure of the Cu{sub 2}ZnSn(S{sub x}Se{sub 1-x}){sub 4} [CZTSSe] films and the band alignment at the interfaces between CdS buffer and the CZTSSe in conjunction with the anion-mixing ratio x = 0-1 have been investigated using in situ X-ray, ultraviolet photoemission spectroscopy (XPS, UPS), and inverse photoemission spectroscopy (IPES). Changes of the UPS and IPES spectra in conjunction with x have revealed that the electronic structure of the CZTSSe surface is characterized with the preferential rise of conduction band minimum (CBM) in conjunction with the increase of x. As x increases, interface induced band bending decreases from 0.5 to 0.6 at the CdS/CZTSe (x = 0) interface to 0.1-0.2 at the CdS/CZTS (x = 1) one. And the downward shift of CBM due to the deposition of the CdS layer is enhanced as x increases. These changes result in the monotonous decrease of conduction band offset (CBO) in conjunction with the increase of x: CBO at the x = 0 and 1 interfaces are +0.5 and -0.14 to -0.15 eV, respectively. The values of CBO are consistent with the device properties; occasional emergence of double junction like current-voltage characteristics in the CdS/CZTSe-based cells, serious voltage-loss in the CdS/CZTS ones, and the highest performance achieved in the CdS/CZTSSe ones. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  15. Probiotic Properties of Lactic Acid Bacteria Isolated from Croatian Fresh Soft Cheese and Serbian White Pickled Cheese

    Directory of Open Access Journals (Sweden)

    Ksenija Uroić

    2014-01-01

    Full Text Available The aim of this study is to gain insight into the probiotic potential of autochthonous lactic acid bacteria (LAB isolated from artisanal fresh soft and white pickled cheeses. Eleven out of 86 LAB isolates from traditionally produced artisanal fresh soft and white pickled cheeses which survived the most rigorous simulated gastrointestinal tract conditions and did not show resistance to antibiotics were subjected to further evaluation for functional probiotic properties. The ability of the examined strains to assimilate cholesterol in the presence of bile salts was strain dependent, with the highest percentage of cholesterol assimilated by strain Lactobacillus brevis BGGO7-28 possessing S-layer proteins on its cell surface. The growth of strains with mannitol or lactulose as the only carbon source was better than with fructooligosaccharides (FOS and inulin as prebiotic substrates, which should be considered in the production of synbiotics. Moreover, the results demonstrated that the strains were highly adhesive to human enterocyte-like Caco-2 cells and to a lesser extent to HT29-MTX cells, with the exception of strain Lb. brevis BGGO7-28, which showed similar percentage of adhesion to both cell lines. This strain was the only one with the acidic cell surface, while other examined strains have the cell surfaces with electron donor and basic properties. In addition, all selected strains decreased the proliferation of gut-associated lymphoid tissue (GALT cells, suggesting possible immunomodulatory potential of the isolates. Finally, the number of viable cells in dry active preparations after lyophilisation depended on the lyoprotectant used (inulin, FOS or skimmed milk, as well as on the strain subjected to lyophilisation. In conclusion, the results obtained in this study demonstrate that particular dairy LAB isolates exhibit strain-specific probiotic properties. Thus, they could be further examined as part of mixed autochthonous starter cultures for

  16. Acoustic and hybrid 3D-printed electrochemical biosensors for the real-time immunodetection of liver cancer cells (HepG2).

    Science.gov (United States)

    Damiati, Samar; Küpcü, Seta; Peacock, Martin; Eilenberger, Christoph; Zamzami, Mazin; Qadri, Ishtiaq; Choudhry, Hani; Sleytr, Uwe B; Schuster, Bernhard

    2017-08-15

    This study presents an efficient acoustic and hybrid three-dimensional (3D)-printed electrochemical biosensors for the detection of liver cancer cells. The biosensors function by recognizing the highly expressed tumor marker CD133, which is located on the surface of liver cancer cells. Detection was achieved by recrystallizing a recombinant S-layer fusion protein (rSbpA/ZZ) on the surface of the sensors. The fused ZZ-domain enables immobilization of the anti-CD133 antibody in a defined manner. These highly accessible anti-CD133 antibodies were employed as a sensing layer, thereby enabling the efficient detection of liver cancer cells (HepG2). The recognition of HepG2 cells was investigated in situ using a quartz crystal microbalance with dissipation monitoring (QCM-D), which enabled the label-free, real-time detection of living cells on the modified sensor surface under controlled conditions. Furthermore, the hybrid 3D additive printing strategy for biosensors facilitates both rapid development and small-scale manufacturing. The hybrid strategy of combining 3D-printed parts and more traditionally fabricated parts enables the use of optimal materials: a ceramic substrate with noble metals for the sensing element and 3D-printed capillary channels to guide and constrain the clinical sample. Cyclic voltammetry (CV) measurements confirmed the efficiency of the fabricated sensors. Most importantly, these sensors offer low-cost and disposable detection platforms for real-world applications. Thus, as demonstrated in this study, both fabricated acoustic and electrochemical sensing platforms can detect cancer cells and therefore may have further potential in other clinical applications and drug-screening studies. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Metal-Silicate-Sulfide Partitioning of U, Th, and K: Implications for the Budget of Volatile Elements in Mercury

    Science.gov (United States)

    Habermann, M.; Boujibar, A.; Righter, K.; Danielson, L.; Rapp, J.; Righter, M.; Pando, K.; Ross, D. K.; Andreasen, R.

    2016-01-01

    During formation of the solar system, the Sun produced strong solar winds, which stripped away a portion of the volatile elements from the forming planets. Hence, it was expected that planets closest to the sun, such as Mercury, are more depleted in volatile elements in comparison to other terrestrial planets. However, the MESSENGER mission detected higher than expected K/U and K/Th ratios on Mercury's surface, indicating a volatile content between that of Mars and Earth. Our experiments aim to resolve this discrepancy by experimentally determining the partition coefficients (D(sup met/sil)) of K, U, and Th between metal and silicate at varying pressure (1 to 5 GPa), temperature (1500 to 1900 C), oxygen fugacity (IW-2.5 to IW-6.5) and sulfur-content in the metal (0 to 33 wt%). Our data show that U, Th, and K become more siderophile with decreasing fO2 and increasing sulfur-content, with a stronger effect for U and Th in comparison to K. Using these results, the concentrations of U, Th, and K in the bulk planet were calculated for different scenarios, where the planet equilibrated at a fO2 between IW-4 and IW-7, assuming the existence of a FeS layer, between the core and mantle, with variable thickness. These models show that significant amounts of U and Th are partitioned into Mercury's core. The elevated superficial K/U and K/Th values are therefore only a consequence of the sequestration of U and Th into the core, not evidence of the overall volatile content of Mercury.

  18. Analysis of the early growth mechanisms during the chemical deposition of CdS thin films by spectroscopic ellipsometry

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval-Paz, M.G., E-mail: myrnasandoval@udec.c [Centro de Investigacion y Estudios Avanzados del IPN. Unidad Queretaro, Apdo. postal 1-798, Queretaro, Qro., 76001 (Mexico); Departamento de Fisica, Facultad de Ciencias Fisicas y Matematicas, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Ramirez-Bon, R. [Centro de Investigacion y Estudios Avanzados del IPN. Unidad Queretaro, Apdo. postal 1-798, Queretaro, Qro., 76001 (Mexico)

    2009-10-30

    Chemically deposited CdS thin films were analyzed in this work by means of the spectroscopic ellipsometry technique. The CdS thin films were deposited from an ammonia-free process at short durations in order to obtain information about the layer microstructure and kinetic growth process. We found that the conditions of the ammonia-free reaction solution promote the ion-by-ion deposition process at the early growth stages yielding a compact, high refraction index and highly crystalline oriented CdS layers. Using a concentration of 1.82 mg/ml of cadmium in the reaction solution, the resulting films possess a double layer microstructure which consists of an inner compact layer and an external porous one. The inner layer is developed during the first 15 min of deposition time and it reaches a thickness around of 80 nm. After this time and on this inner layer of CdS, it grows an external porous layer whose thickness increases with the deposition time. The formation of the CdS compact layer at the early stages is related with the ion-by-ion growth mechanism. The subsequent CdS porous layer is formed during the cluster-by-cluster growth stage at longer deposition times. By reducing the cadmium concentration in reaction solution down to 0.76 mg/ml, maintaining constant molar ratio concentrations of Cd/complexing and Cd/thiourea, the chemically deposited CdS films develop only the inner compact layer with a thickness of about 80 nm after 35 min of deposition time.

  19. Optical and structural properties of chemically deposited CdS thin films on polyethylene naphthalate substrates

    Energy Technology Data Exchange (ETDEWEB)

    Sandoval-Paz, M.G., E-mail: myrnasandoval@udec.cl [Departamento de Fisica, Facultad de Ciencias Fisicas y Matematicas, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile); Ramirez-Bon, R. [Centro de Investigacion y Estudios Avanzados del IPN, Unidad Queretaro, Apdo. Postal 1-798, 76001 Queretaro, Qro. (Mexico)

    2011-11-30

    CdS thin films were deposited on polyethylene naphthalate substrates by means of the chemical bath deposition technique in an ammonia-free cadmium-sodium citrate system. Three sets of CdS films were grown in precursor solutions with different contents of Cd and thiourea maintaining constant the concentration ratios [Cd]/[thiourea] and [Cd]/[sodium citrate] at 0.2 and 0.1 M/M, respectively. The concentrations of cadmium in the reaction solutions were 0.01, 7.5 Multiplication-Sign 10{sup -3} and 6.8 Multiplication-Sign 10{sup -3} M, respectively. The three sets of CdS films were homogeneous, hard, specularly reflecting, yellowish and adhered very well to the plastic substrates, quite similar to those deposited on glass substrates. The structural and optical properties of the CdS films were determined from X-ray diffraction, optical transmission and reflection spectroscopy and atomic force microscopy measurements. We found that the properties of the films depend on both the amount of Cd in the growth solutions and on the deposition time. The increasing of Cd concentration in the reaction solution yield to thicker CdS films with smaller grain size, shorter lattice constant, and higher energy band gap. The energy band gap of the CdS films varied in the range 2.42-2.54 eV depending on the precursor solution. The properties of the films were analyzed in terms of the growth mechanisms during the chemical deposition of CdS layers.

  20. Quantum dot-dye hybrid systems for energy transfer applications

    International Nuclear Information System (INIS)

    Ren, Ting

    2010-01-01

    In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems. In the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stoeber silica particles with an outer silica shell of thickness 2-24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. New QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability, our QD

  1. Forschungszentrum Rossendorf, Institute of Radiochemistry. Annual report 2004

    International Nuclear Information System (INIS)

    Bernhard, G.

    2005-01-01

    The Institute of Radiochemistry (IRC), one of the six Institutes of the Forschungszentrum Rossendorf (FZR) performs basic and applied research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Because of their high radiotoxicity and long half-life the actinides are of special interest. The research is focused on a better understanding of the chemical behavior of actinides in the environment on a molecular level. We will increase our efforts to study both the speciation of actinides on bio-molecular interfaces and their transport in bio-systems. Current topics of our research work are: aquatic chemistry of actinides, actinides in bio-systems, interaction of actinides with solid phases, Reactive transport of actinides. About 60 scientists, technicians and PhD students are employed at the Institute of Radiochemistry. We accomplished many new scientific results in the past year, which are presented in this annual report. Among them only few can be highlighted in this preface. Further progress was achieved in understanding the formation and characterization of uranium containing colloids. The newly installed method of laser-induced breakdown detection was very helpful for the identification of uranium colloids under anoxic conditions. We were very successful in the determination of formation pathways and structure of various actinide complexes. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces. The results achieved in the characterization of the properties, modification, and interaction of the S-layers of Bacillus sphaericus with uranium and some other heavy metals strengthen our hope to use this

  2. Investigation of Liraglutide Effects on Changes of Uterine Tissue and Estradiol and FSH Hormones in NMRI Mice

    Directory of Open Access Journals (Sweden)

    Sara Atashnezhad

    2017-06-01

    Full Text Available Background & aim: Liraglutide has used for treatment of obesity and type 2 diabetes, which are main factors of infertility. Regarding that, uterus as the most important organ reproductive system is under vulnerable, particularly by chemical drugs, in this research the effects of Liraglutide on uterine tissue changes and Estradiol and FSH hormones in NMRI mice in In vivo condition has been investigated. Methods: This experimental study has been done on 28 adult female NMRI mice (8 to 12 weeks that have been selected with body weight between 25 and 30 grams. Female mice were randomly divided into four groups (including 7 mice: control, sham and two experimental groups. Control mice received no treatment, experimental and sham groups were injected Liraglutide with 0.6 and 1.8 mg/kg density and solution for 30 days respectively. All injection were daily and subcutaneously. After 30 days injection, the mice were deeply anesthetized and in addition to blood sampling, mice’s uterus was removed and the one-third of right middle part of the uterus has been investigated as tissue studies. Following histochemical staining, the samples were studied using light and transmission electron microcopies. The collected data were analyzed using one-way analyses (ANOVA and Tukey test. Results: The results of using Liraglutide has been shown mice’s weight of experimental groups (1 and 2, compared with sham and control groups, have marked decrease (p<0.01 and (p<0.001 respectively. Also, uterus’s layers (from lumen until last layer and lumen diameter, have marked decrease (p<0.05 and (p<0.01 respectively in experimental groups. In experimental group 2 thickness of the perimetrium has marked decrease (p<0.05, also Endometrium’s thickness in experimental groups 1 and 2, compared with sham and control groups, has shown marked decrease (p<0.01 and (p<0.001 respectively. In addition the number of uterus glands have marked increased (p<0.05 and (p<0.05 in

  3. Deep ice and salty oceans of icy worlds, how high pressures influence their thermodynamics and provide constrains on extraterrestrial habitability

    Science.gov (United States)

    Journaux, B.; Brown, J. M.; Bollengier, O.; Abramson, E.

    2017-12-01

    As in Earth arctic and Antarctic regions, suspected extraterrestrial deep oceans in icy worlds (i.e. icy moons and water-rich exoplanets) chemistry and thermodynamic state will strongly depend on their equilibrium with H2O ice and present solutes. Na-Mg-Cl-SO4 salt species are currently the main suspected ionic solutes to be present in deep oceans based on remote sensing, magnetic field measurements, cryovolcanism ice grains chemical analysis and chondritic material aqueous alteration chemical models. Unlike on our planet, deep extraterrestrial ocean might also be interacting at depth with high pressure ices (e.g. III, V, VI, VI, X) which have different behavior compared to ice Ih. Unfortunately, the pressures and temperatures inside these hydrospheres differ significantly from the one found in Earth aqueous environments, so most of our current thermodynamic databases do not cover the range of conditions relevant for modeling realistically large icy worlds interiors. Recent experimental results have shown that the presence of solutes, and more particularly salts, in equilibrium with high pressure ices have large effects on the stability, buoyancy and chemistry of all the phases present at these extreme conditions. High pressure in-situ measurements using diamond anvil cell apparatus were operated both at the University of washington and at the European Synchrotron Radiation Facility on aqueous systems phase diagrams with Na-Mg-Cl-SO4 species, salt incorporation in high pressure ices and density inversions between the solid and the fluids. These results suggest a more complex picture of the interior structure, dynamic and chemical evolution of large icy worlds hydrospheres when solutes are taken into account, compared to current models mainly using pure water. Based on our in-situ experimental measurements, we propose the existence of new liquid environments at greater depths and the possibility of solid state transport of solute through the high pressure ices(s

  4. Brook trout (Salvelinus fontinalis extinction in small boreal lakes revealed by ephippia pigmentation: a preliminary analysis

    Directory of Open Access Journals (Sweden)

    Alexandre Bérubé Tellier

    2016-12-01

    were observed between the 1990's and 1950's layers within each lake. This suggests that brook trout extinction already occurred before the 1950’s, or that brook trout population abundance was already extremely low before and after the 1990’s. Our preliminary study shows that ephippium pigmentation can be used as a tool to quickly assess present and past predation levels on zooplankton when only sediment samples are available.

  5. The animal model determines the results of Aeromonas virulence factors

    Directory of Open Access Journals (Sweden)

    Alejandro Romero

    2016-10-01

    Full Text Available The selection of an experimental animal model is of great importance in the study of bacterial virulence factors. Here, a bath infection of zebrafish larvae is proposed as an alternative model to study the virulence factors of A. hydrophila. Intraperitoneal infections in mice and trout were compared with bath infections in zebrafish larvae using specific mutants. The great advantage of this model is that bath immersion mimics the natural route of infection, and injury to the tail also provides a natural portal of entry for the bacteria. The implication of T3SS in the virulence of A. hydrophila was analysed using the AH-1::aopB mutant. This mutant was less virulent than the wild-type strain when inoculated into zebrafish larvae, as described in other vertebrates. However, the zebrafish model exhibited slight differences in mortality kinetics only observed using invertebrate models. Infections using the mutant AH-1∆vapA lacking the gene coding for the surface S-layer suggested that this protein was not totally necessary to the bacteria once it was inside the host, but it contributed to the inflammatory response. Only when healthy zebrafish larvae were infected did the mutant produce less mortality than the wild type. Variations between models were evidenced using the AH-1∆rmlB, which lacks the O-antigen lipopolysaccharide (LPS, and the AH-1∆wahD, which lacks the O-antigen LPS and part of the LPS outer-core. Both mutants showed decreased mortality in all of the animal models, but the differences between them were only observed in injured zebrafish larvae, suggesting that residues from the LPS outer core must be important for virulence. The greatest differences were observed using the AH-1ΔFlaB-J (lacking polar flagella and unable to swim and the AH-1::motX (non-motile but producing flagella. They were as pathogenic as the wild-type strain when injected into mice and trout, but no mortalities were registered in zebrafish larvae. This study

  6. Multivalent Chromosomal Expression of the Clostridium botulinum Serotype A Neurotoxin Heavy-Chain Antigen and the Bacillus anthracis Protective Antigen in Lactobacillus acidophilus.

    Science.gov (United States)

    O'Flaherty, Sarah; Klaenhammer, Todd R

    2016-10-15

    Clostridium botulinum and Bacillus anthracis produce potent toxins that cause severe disease in humans. New and improved vaccines are needed for both of these pathogens. For mucosal vaccine delivery using lactic acid bacteria, chromosomal expression of antigens is preferred over plasmid-based expression systems, as chromosomal expression circumvents plasmid instability and the need for antibiotic pressure. In this study, we constructed three strains of Lactobacillus acidophilus NCFM expressing from the chromosome (i) the nontoxic host receptor-binding domain of the heavy chain of Clostridium botulinum serotype A neurotoxin (BoNT/A-Hc), (ii) the anthrax protective antigen (PA), and (iii) both the BoNT/A-Hc and the PA. The BoNT/A-Hc vaccine cassette was engineered to contain the signal peptide from the S-layer protein A from L. acidophilus and a dendritic-cell-targeting peptide. A chromosomal region downstream of lba0889 carrying a highly expressed enolase gene was selected for insertion of the vaccine cassettes. Western blot analysis confirmed the heterologous expression of the two antigens from plasmid and chromosome locations. Stability assays demonstrated loss of the vaccine cassettes from expression plasmids without antibiotic maintenance. RNA sequencing showed high expression of each antigen and that insertion of the vaccine cassettes had little to no effect on the transcription of other genes in the chromosome. This study demonstrated that chromosomal integrative recombinant strains are promising vaccine delivery vehicles when targeted into high-expression chromosomal regions. Levels of expression match high-copy-number plasmids and eliminate the requirement for antibiotic selective maintenance of recombinant plasmids. Clostridium botulinum and Bacillus anthracis produce potent neurotoxins that pose a biochemical warfare concern; therefore, effective vaccines against these bacteria are required. Chromosomal expression of antigens is preferred over plasmid

  7. Artificial twin-layer configurations of Zn(O,S) films by radio frequency sputtering in all dry processed eco-friendly Cu(In,Ga)Se2 solar cells

    Science.gov (United States)

    Liu, Wei; Fan, Yu; Li, Xiaodong; Lin, Shuping; Liu, Yang; Shi, Sihan; Wang, He; Zhou, Zhiqiang; Zhang, Yi; Sun, Yun

    2018-03-01

    Cu(In,Ga)Se2 thin film solar cells are of great interest for research and industrial applications with their high conversion efficiencies, long-term stability and significant lifetimes. Such a solar cell of a p-n junction consists of p-type Cu(In,Ga)Se2 films as a light absorber and n-type CdS as a buffer layer, which often emerges with intrinsic ZnO. Aimed at eco-friendly fabrication protocols, a large number of strategies have been investigated to fabricate a Cd-free n-type buffer layer such as Zn(O,S) in Cu(In,Ga)Se2 solar cells. Also, if the Zn(O,S) films are prepared by coevaporation or sputtering, it will offer high compatibility with the preferred mass production. Here, we propose and optimize a dry method for Zn(O,S) deposition in a radio frequency sputtering. In particular, the strategy for the twin-layer configurations of Zn(O,S) films not only greatly improve their electrical conductance and suppress charge carrier recombination, but also avoid degradation of the Zn(O,S)/Cu(In,Ga)Se2 interfaces. Indeed, the high quality of such twin Zn(O,S) layers have been reflected in the similar conversion efficiencies of the complete solar cells as well as the large short-circuit current density, which exceeds the CdS reference device. In addition, Zn(O,S) twin layers have reduced the production time and materials by replacing the CdS/i-ZnO layers, which removes two fabrication steps in the multilayered thin film solar cells. Furthermore, the device physics for such improvements have been fully unveiled with both experimental current–voltage and capacitance–voltage spectroscopies and device simulations via wxAMPS program. Finally, the proposed twin-layer Zn(O,S)/Cu(In,Ga)Se2 interfaces account for the broadening of the depletion region of photogenerated charge carriers, which greatly suppress the carrier recombination at the space charge region, and eventually lead to the more efficient collection of charge carriers at both electrodes.

  8. Characterization of extracellular virulence properties and biofilm-formation capacity of Vibrio species recovered from ready-to-eat (RTE) shrimps.

    Science.gov (United States)

    Beshiru, Abeni; Igbinosa, Etinosa O

    2018-04-11

    In this study, we evaluated the virulence factor production, biofilm-forming ability and cell surface properties of ready-to-eat shrimps associated vibrios strains. A total of 1440 ready-to-eat (RTE) shrimp samples were purchased from open markets in southern Nigeria, from November 2016 to October 2017. Biofilm formation was carried out using the microtitre plate method. Cell-to-cell adhesion of Vibrio species was assessed via surface hydrophobicity using the bacterial adherence to hydrocarbons (BATH) and salting aggregation technique, autoaggregation and coaggregation assay. The virulence potential of the identified 120 Vibrio strains includes haemolysis 107 (89.17%), lipase 106 (88.33%), protease 108 (90%), gelatinase 111 (92.5%), the presence of surface-layer (S-layer) 109 (90.8%) and DNA degrading activity 107 (89.17%). Biofilm formation at 30 °C tryptone soy broth in dynamic conditions revealed total biofilm producers for the Vibrio species as follows: V. parahaemolyticus (95.65%), V. vulnificus (92.86%), V. fluvialis (91.67%), V. alginolyticus (87.5%), V. cholerae (100%), V. mimicus (90%), V. harveyi (66.7%), and other Vibrio spp. (84%). A total of 50 biofilm producing vibrios using BATH technique include 49 (98%) hydrophilic and 1 (2%) moderately hydrophobic. Using the modified salting aggregation technique, 50 (100%) was characterized as hydrophilic. Autoaggregation index for the 12 biofilms producing Vibrio strains ranged from 11.6 to 41.3%, while the autoaggregation index for the 12 test bacteria ranged from 26.2 to 71.3%. Coaggregation between the 12 test bacteria with the 12 Vibrio strains ranged from 9.3 to 78.5%. However most vibrios in this study were hydrophilic, their hydrophilic potential is important for their capability to autoaggregate and coaggregate. Findings on the specific process by which virulent Vibrio spp. form biofilm and adhere to shrimp surface as attached plankton may assist in monitoring epidemics of the pathogen. Copyright

  9. Understanding Urban Watersheds through Digital Interactive Maps, San Francisco Bay Area, California

    Science.gov (United States)

    Sowers, J. M.; Ticci, M. G.; Mulvey, P.

    2014-12-01

    Dense urbanization has resulted in the "disappearance" of many local creeks in urbanized areas surrounding the San Francisco Bay. Long reaches of creeks now flow in underground pipes. Municipalities and water agencies trying to reduce non-point-source pollution are faced with a public that cannot see and therefore does not understand the interconnected nature of the drainage system or its ultimate discharge to the bay. Since 1993, we have collaborated with the Oakland Museum, the San Francisco Estuary Institute, public agencies, and municipalities to create creek and watershed maps to address the need for public understanding of watershed concepts. Fifteen paper maps are now published (www.museumca.org/creeks), which have become a standard reference for educators and anyone working on local creek-related issues. We now present digital interactive creek and watershed maps in Google Earth. Four maps are completed covering urbanized areas of Santa Clara and Alameda Counties. The maps provide a 3D visualization of the watersheds, with cartography draped over the landscape in transparent colors. Each mapped area includes both Present and Past (circa 1800s) layers which can be clicked on or off by the user. The Present layers include the modern drainage network, watershed boundaries, and reservoirs. The Past layers include the 1800s-era creek systems, tidal marshes, lagoons, and other habitats. All data are developed in ArcGIS software and converted to Google Earth format. To ensure the maps are interesting and engaging, clickable icons pop-up provide information on places to visit, restoration projects, history, plants, and animals. Maps of Santa Clara Valley are available at http://www.valleywater.org/WOW.aspx. Maps of western Alameda County will soon be available at http://acfloodcontrol.org/. Digital interactive maps provide several advantages over paper maps. They are seamless within each map area, and the user can zoom in or out, and tilt, and fly over to explore

  10. Interaction of Extreme Halophilic Archaea With the Evaporites of the Solar Salterns Guerrero Negro Baja California, Mexico

    Science.gov (United States)

    Tamez, P.; Lopez-Cortés, A.

    2008-12-01

    Hypersaline environments have been significant reservoirs for the long-term evolution of specifically adapted microorganisms. Characterized to have higher salt concentrations (up to 35 g/L), they are worldwide distributed and have a commercial significance. Exportadora de Sal, Guerrero Negro, Mexico has a multipond salterns system designed to harvest common salt (NaCl) from sea water. To achieve this purpose, sea water is pumped through a set of shallow ponds where water evaporates and salts concentrate. Sequential precipitation of CaCO3, CaSO4 2H2O and NaCl occurs in a mineral formations call it evaporites. In the interior of those gypsum-encrusted and halite-encrusted minerals, communities of extremely salt-loving archaea prosper. Previous studies have showed the influence of Haloarchaeal cells in the formation of larger fluid inclusions than crystals formed in sterile salt solutions. S-layer envelopes and cells of Haloarcula strain SP8807 contributed to the nucleation of new crystals of NaCl. Given the significance of the scope in phylogenetic archaeal diversity research, this study had a polyphasic approach. SEM micrographs from a 21- 31% (w/v) gradient salt multipond system evaporites, gave an insight profile of the extreme halophilic archaeal communities thriving in the surface of the gypsum and halite evaporites. Halite crystals were form after 21 days of incubation in solid medium with archaeal cells. Both culture and non-culture dependent methods, Nested-PCR-DGGE analysis and sequencing of 16S rDNA amplified fragment genes from environmental samples and isolated strains were used for this purpose. We isolate three strains from Pond 9 (21.07% total salt concentration) and one strain from Cristallizer 20 (25.15% total salt concentration). 16S rDNA signaling gave 99% of similarity with Halogeometricum borinquense, sequence AF002984, two other strains were 99% of similarity with Halobacterium salinarum, sequence AJ496185 these strains shown different colony

  11. The LANDFIRE Total Fuel Change Tool (ToFuΔ) user’s guide

    Science.gov (United States)

    Smail, Tobin; Martin, Charley; Napoli, Jim

    2011-01-01

    LANDFIRE fuel data were originally developed from coarse-scale existing vegetation type, existing vegetation cover, existing vegetation height, and biophysical setting layers. Fire and fuel specialists from across the country provided input to the original LANDFIRE National (LF_1.0.0) fuel layers to help calibrate fuel characteristics on a more localized scale. The LANDFIRE Total Fuel Change Tool (ToFu∆) was developed from this calibration process. Vegetation is subject to constant change – and fuels are therefore also dynamic, necessitating a systematic method for reflecting changes spatially so that fire behavior can be accurately accessed. ToFuΔ allows local experts to quickly produce maps that spatially display any proposed fuel characteristics changes. ToFu∆ works through a Microsoft Access database to produce spatial results in ArcMap based on rule sets devised by the user that take into account the existing vegetation type (EVT), existing vegetation cover (EVC), existing vegetation height (EVH), and biophysical setting (BpS) from the LANDFIRE grid data. There are also options within ToFu∆ to add discrete variables in grid format through use of the wildcard option and for subdividing specific areas for different fuel characteristic assignments through the BpS grid. The ToFu∆ user determines the size of the area for assessment by defining a Management Unit, or “MU.” User-defined rule sets made up of EVT, EVC, EVH, and BpS layers, as well as any wildcard selections, are used to change or refine fuel characteristics within the MU. Once these changes have been made to the fuel characteristics, new grids are created for fire behavior analysis or planning. These grids represent the most common ToFu∆ output. ToFuΔ is currently under development and will continue to be updated in the future. The current beta version (0.12), released in March 2011, is compatible with Windows 7 and will be the last release until the fall of 2011.

  12. Characterization of CuInS{sub 2} thin films prepared by chemical bath deposition and their implementation in a solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Lugo, S.; López, I. [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria 66451, San Nicolás de los Garza, Nuevo León, México (Mexico); Peña, Y., E-mail: yolapm@gmail.com [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria 66451, San Nicolás de los Garza, Nuevo León, México (Mexico); Calixto, M. [Instituto de Energías Renovables, Universidad Nacional Autónoma de México, C.P. 62580, Temixco, Morelos, México (Mexico); Hernández, T. [Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Químicas, Laboratorio de Materiales I, Av. Universidad, Cd. Universitaria 66451, San Nicolás de los Garza, Nuevo León, México (Mexico); Messina, S. [Universidad Autónoma de Nayarit, Ciudad de la Cultura “Amado Nervo”, S/N C.P. 63155, Tepic, Nayarit, México (Mexico); and others

    2014-10-31

    CuInS{sub 2} thin films were formed by the sequential deposition of In{sub 2}S{sub 3}–CuS layers on glass substrates, by chemical bath deposition technique, and heating these multilayer 1 h at 350 °C and 400 mPa. The morphology and thickness of the CuInS{sub 2} thin films were analysed by scanning electron microscopy, showing particles with elongated shape and length about 40 nm, and thickness of 267 and 348 nm for samples from 15 and 24 h of deposition time in the chemical bath of In{sub 2}S{sub 3}, respectively. The energy band gap values of the films were around 1.4 eV, whereas the electrical conductivity showed values from 64.91 to 4.11 × 10{sup −3} Ω{sup −1} cm{sup −1} for the samples of 15 and 24 h of In{sub 2}S{sub 3} deposition bath, respectively. The obtained CuInS{sub 2} films showed appropriate values for their application as an absorbing layer in photovoltaic structures of the type: glass/SnO{sub 2}:F/CdS/Sb{sub 2}S{sub 3}/CuInS{sub 2}/PbS/C/Ag. The whole structure was obtained through chemical bath deposition technique. The solar cell corresponding to 15 h of In{sub 2}S{sub 3} deposition duration bath showed energy-conversion efficiency (η) of 0.53% with open circuit voltage (V{sub oc}) of 530 mV, short circuit current density (J{sub sc}) of 2.43 mA cm{sup −2}, and fill factor (FF) of 0.41. In the case of the structure with 24 h of deposition of In{sub 2}S{sub 3} bath, η = 0.43% was measured with the following parameters: V{sub oc} = 330 mV, J{sub sc} = 4.78 mA cm{sup −2} and FF = 0.27. - Highlights: • CuInS{sub 2} films were formed by chemical bath deposition followed by a heat treatment. • Prepared CuInS{sub 2} thin films can work as an effective absorbing layer in a solar cell. • A complete solar cell structure was made by a chemical bath deposition method.

  13. Identification of genes involved in the biosynthesis of the third and fourth sugars of the Methanococcus maripaludis archaellin N-linked tetrasaccharide.

    Science.gov (United States)

    Ding, Yan; Jones, Gareth M; Uchida, Kaoru; Aizawa, Shin-Ichi; Robotham, Anna; Logan, Susan M; Kelly, John; Jarrell, Ken F

    2013-09-01

    N-glycosylation is a protein posttranslational modification found in all three domains of life. Many surface proteins in Archaea, including S-layer proteins, pilins, and archaellins (archaeal flagellins) are known to contain N-linked glycans. In Methanococcus maripaludis, the archaellins are modified at multiple sites with an N-linked tetrasaccharide with the structure Sug-1,4-β-ManNAc3NAmA6Thr-1,4-β-GlcNAc3NAcA-1,3-β-GalNAc, where Sug is the unique sugar (5S)-2-acetamido-2,4-dideoxy-5-O-methyl-α-l-erythro-hexos-5-ulo-1,5-pyranose. In this study, four genes--mmp1084, mmp1085, mmp1086, and mmp1087--were targeted to determine their potential involvement of the biosynthesis of the sugar components in the N-glycan, based on bioinformatics analysis and proximity to a number of genes which have been previously demonstrated to be involved in the N-glycosylation pathway. The genes mmp1084 to mmp1087 were shown to be cotranscribed, and in-frame deletions of each gene as well as a Δmmp1086Δmmp1087 double mutant were successfully generated. All mutants were archaellated and motile. Mass spectrometry examination of purified archaella revealed that in Δmmp1084 mutant cells, the threonine linked to the third sugar of the glycan was missing, indicating a putative threonine transferase function of MMP1084. Similar analysis of the archaella of the Δmmp1085 mutant cells demonstrated that the glycan lacked the methyl group at the C-5 position of the terminal sugar, indicating that MMP1085 is a methyltransferase involved in the biosynthesis of this unique sugar. Deletion of the remaining two genes, mmp1086 and mmp1087, either singularly or together, had no effect on the structure of the archaellin N-glycan. Because of their demonstrated involvement in the N-glycosylation pathway, we designated mmp1084 as aglU and mmp1085 as aglV.

  14. Impurity of Sulfur Layers and Magmatic Gas Scrubbing: Implications for Gas Monitoring

    Science.gov (United States)

    Scolamacchia, T.

    2017-12-01

    The evidence of bodies of elemental sulfur (Se) beneath acid crater lakes at the summit of composite active volcanoes has been recognized several decades ago (Oppenheimer and Stevenson, 1989; Christenson and Woods, 1993). But Se accumulation was already hypothesized a century ago at Kusatzu Shirane (Japan) based on the observation of sulfur spherules floating on its crater-lake (Ohashi, 1919). Since these pioneering works, other studies have focused on understanding key aspects of molten sulfur bodies, considered a feature unique of volcanic lakes. Instead, it is reasonable to assume that Se bodies occur in several volcanic settings because a) several reactions may lead to Se deposition from S-bearing gases, and b) crater-lakes, surface expressions of hydrothermal systems, are transient features. The scrubbing of several magmatic gases, some of which critical for volcano monitoring, has been attributed to ground/surface waters (Symonds et al. 2001). Nevertheless, gas scrubbing could reflect viscosity variations of impure Se within hydrothermal systems. Industrial experiments indicated that impurities (organics, H2S, ammonia, HCl, HF, HBr, HI) hinder Se polymerization at T ≥ 160ºC, allowing viscosity to remain low for long time depending on the maximum T achieved and heating rates (Bacon and Fanelli, 1943). However, a prolonged heating destroys the viscosity-modifying substances (e.g. H2Sx formed by reactions with organics, H2S, or ammonia) and dramatic Se viscosity increases occur after a certain number of heating and cooling cycles. A prolonged boiling of Se with organics was observed to release H2S, following H2Sx disruption. Some gases (e.g. SO2) do not affect Se viscosity. In volcanic environments gases such as SO2, CO2 could escape under Selow viscosity regimes. Also, halogens absence in gas emissions could be caused by their participation in reactions within S-layers causing its viscosity to remain low. More data are needed to validate the hypothesis

  15. Localization and structural analysis of a conserved pyruvylated epitope in Bacillus anthracis secondary cell wall polysaccharides and characterization of the galactose-deficient wall polysaccharide from avirulent B. anthracis CDC 684.

    Science.gov (United States)

    Forsberg, L Scott; Abshire, Teresa G; Friedlander, Arthur; Quinn, Conrad P; Kannenberg, Elmar L; Carlson, Russell W

    2012-08-01

    Bacillus anthracis CDC 684 is a naturally occurring, avirulent variant and close relative of the highly pathogenic B. anthracis Vollum. Bacillus anthracis CDC 684 contains both virulence plasmids, pXO1 and pXO2, yet is non-pathogenic in animal models, prompting closer scrutiny of the molecular basis of attenuation. We structurally characterized the secondary cell wall polysaccharide (SCWP) of B. anthracis CDC 684 (Ba684) using chemical and NMR spectroscopy analysis. The SCWP consists of a HexNAc trisaccharide backbone having identical structure as that of B. anthracis Pasteur, Sterne and Ames, →4)-β-d-ManpNAc-(1 → 4)-β-d-GlcpNAc-(1 → 6)-α-d-GlcpNAc-(1→. Remarkably, although the backbone is fully polymerized, the SCWP is the devoid of all galactosyl side residues, a feature which normally comprises 50% of the glycosyl residues on the highly galactosylated SCWPs from pathogenic strains. This observation highlights the role of defective wall assembly in virulence and indicates that polymerization occurs independently of galactose side residue attachment. Of particular interest, the polymerized Ba684 backbone retains the substoichiometric pyruvate acetal, O-acetate and amino group modifications found on SCWPs from normal B. anthracis strains, and immunofluorescence analysis confirms that SCWP expression coincides with the ability to bind the surface layer homology (SLH) domain containing S-layer protein extractable antigen-1. Pyruvate was previously demonstrated as part of a conserved epitope, mediating SLH-domain protein attachment to the underlying peptidoglycan layer. We find that a single repeating unit, located at the distal (non-reducing) end of the Ba684 SCWP, is structurally modified and that this modification is present in identical manner in the SCWPs of normal B. anthracis strains. These polysaccharides terminate in the sequence: (S)-4,6-O-(1-carboxyethylidene)-β-d-ManpNAc-(1 → 4)-[3-O-acetyl]-β-d-GlcpNAc-(1 → 6)-α-d-GlcpNH(2)-(1→.

  16. TEM study of the (SbS){sub 1+δ}(NbS{sub 2}){sub n}, (n=1, 2, 3; δ~1.14, 1.20) misfit layer phases

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Herrero, A., E-mail: adriangh@pdi.ucm.es [ICTS Centro Nacional de Microscopía Electrónica, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Landa-Cánovas, A.R. [Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, E-28049 Madrid (Spain); Otero-Díaz, L.C. [Dpto. Química Inorgánica, Fac. CC. Químicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2015-10-15

    In the Sb–Nb–S system four new misfit layer phases have been found and carefully investigated via Transmission Electron Microscopy (TEM). Their structures are of composite modulated structure type with stoichiometries that can be formulated as (SbS){sub 1+δ}(NbS{sub 2}){sub n}; for n=1, δ~1.14 and 1.19; for n=2, δ~1.18 and for n=3, δ~1.19. Selected Area Electron Diffraction (SAED) patterns show an almost commensurate fit between the pseudo-tetragonal (SbS) and the pseudo-orthohexagonal (NbS{sub 2}){sub n} subcells along the misfit direction a, with 3(SbS)≈5(NbS{sub 2}), being b the same for both sub-lattices and c the stacking direction. For n=1, a commensurate phase with 4a{sub SbS}=7a{sub NbS2} has also been observed. In addition to the characteristic misfit and associated modulation of the two sub-structures, a second modulation is also present which appears to be primarily associated with the (SbS) sub-structure of both the n=1 and n=2 phases. High Resolution Transmission Electron Microscopy (HRTEM) images show ordered stacking sequences between the (SbS) and (NbS{sub 2}){sub n} lamellae for each of the four phases, however, disordered intergrowths were also occasionally found. Most of the crystals showed different kinds of twinning defects on quite a fine scale. Many crystals showed curled up edges. In some cases the lamellar crystals were entirely folded giving rise to similar diffraction patterns as found for cylindrical crystals. - Graphical abstract: Idealized structure models of the first three members of the homologous series (SbS){sub 1+δ}(NbS{sub 2}){sub n}. - Highlights: • Transmission Electron Microscopy study of misfit layer sulfides (SbS){sub 1+δ}(NbS{sub 2}){sub n}. • The structures consist of a (SbS) layer interleaved between n (NbS{sub 2}) layers. • Two different members n=1, one n=2 and one n=3 have been studied. • Twinning, intergrowths and different modulations in the (SbS) substructure.

  17. Preparation and characterization of pulsed laser deposited a novel CdS/CdSe composite window layer for CdTe thin film solar cell

    International Nuclear Information System (INIS)

    Yang, Xiaoyan; Liu, Bo; Li, Bing; Zhang, Jingquan; Li, Wei; Wu, Lili; Feng, Lianghuan

    2016-01-01

    Highlights: • Novel CdS/CdSe composite windows for CdTe cell were prepared by pulsed laser deposition. • SEM images show that CdS/CdSe composite windows are stacking together as the design. • CdTe cells with CdS/CdSe composite windows improved the blue response. • CdTe cells with composite windows show an obvious red shift in the absorption edge. • The volume proportion of CdSe affects the performance of CdTe solar cell. - Abstract: A novel CdS/CdSe composite window structure was designed and then the corresponding films were prepared by pulsed laser deposition as an improved window layer for CdTe-based solar cells. Two types of this composite window structure with 5 cycles and 10 cycles CdS/CdSe respectively both combined with CdS layers were prepared at 200 °C compared with pure CdS window layer and finally were applied into CdTe thin film solar cells. The cross section and surface morphology of the two composite window layers were monitored by using scanning electron microscopy and the result shows that the pulsed laser deposited composite window layers with good crystallinity are stacking together as the design. The devices based on CdS/CdSe composite window layers have demonstrated the enhanced photocurrent collection from both short and long wavelength regions compared to CdS/CdTe solar cell. The efficiency of the best reference CdS/CdTe solar cell was 10.72%. And the device with 5 cycles CdS/CdSe composite window showed efficiency of 12.61% with V OC of 772.92 mV, J SC of 25.11 mA/cm 2 and FF of 64.95%. In addition, there are some differences which exist within the optical transmittance spectra and QE curves between the two CdS/CdSe composite window samples, indicating that the volume proportion of CdSe may influence the performance of CdTe thin film solar cell.

  18. Preparation and characterization of pulsed laser deposited a novel CdS/CdSe composite window layer for CdTe thin film solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoyan; Liu, Bo; Li, Bing, E-mail: libing70@126.com; Zhang, Jingquan; Li, Wei; Wu, Lili; Feng, Lianghuan

    2016-03-30

    Highlights: • Novel CdS/CdSe composite windows for CdTe cell were prepared by pulsed laser deposition. • SEM images show that CdS/CdSe composite windows are stacking together as the design. • CdTe cells with CdS/CdSe composite windows improved the blue response. • CdTe cells with composite windows show an obvious red shift in the absorption edge. • The volume proportion of CdSe affects the performance of CdTe solar cell. - Abstract: A novel CdS/CdSe composite window structure was designed and then the corresponding films were prepared by pulsed laser deposition as an improved window layer for CdTe-based solar cells. Two types of this composite window structure with 5 cycles and 10 cycles CdS/CdSe respectively both combined with CdS layers were prepared at 200 °C compared with pure CdS window layer and finally were applied into CdTe thin film solar cells. The cross section and surface morphology of the two composite window layers were monitored by using scanning electron microscopy and the result shows that the pulsed laser deposited composite window layers with good crystallinity are stacking together as the design. The devices based on CdS/CdSe composite window layers have demonstrated the enhanced photocurrent collection from both short and long wavelength regions compared to CdS/CdTe solar cell. The efficiency of the best reference CdS/CdTe solar cell was 10.72%. And the device with 5 cycles CdS/CdSe composite window showed efficiency of 12.61% with V{sub OC} of 772.92 mV, J{sub SC} of 25.11 mA/cm{sup 2} and FF of 64.95%. In addition, there are some differences which exist within the optical transmittance spectra and QE curves between the two CdS/CdSe composite window samples, indicating that the volume proportion of CdSe may influence the performance of CdTe thin film solar cell.

  19. Infrastructure Systems for Advanced Computing in E-science applications

    Science.gov (United States)

    Terzo, Olivier

    2013-04-01

    In the e-science field are growing needs for having computing infrastructure more dynamic and customizable with a model of use "on demand" that follow the exact request in term of resources and storage capacities. The integration of grid and cloud infrastructure solutions allows us to offer services that can adapt the availability in terms of up scaling and downscaling resources. The main challenges for e-sciences domains will on implement infrastructure solutions for scientific computing that allow to adapt dynamically the demands of computing resources with a strong emphasis on optimizing the use of computing resources for reducing costs of investments. Instrumentation, data volumes, algorithms, analysis contribute to increase the complexity for applications who require high processing power and storage for a limited time and often exceeds the computational resources that equip the majority of laboratories, research Unit in an organization. Very often it is necessary to adapt or even tweak rethink tools, algorithms, and consolidate existing applications through a phase of reverse engineering in order to adapt them to a deployment on Cloud infrastructure. For example, in areas such as rainfall monitoring, meteorological analysis, Hydrometeorology, Climatology Bioinformatics Next Generation Sequencing, Computational Electromagnetic, Radio occultation, the complexity of the analysis raises several issues such as the processing time, the scheduling of tasks of processing, storage of results, a multi users environment. For these reasons, it is necessary to rethink the writing model of E-Science applications in order to be already adapted to exploit the potentiality of cloud computing services through the uses of IaaS, PaaS and SaaS layer. An other important focus is on create/use hybrid infrastructure typically a federation between Private and public cloud, in fact in this way when all resources owned by the organization are all used it will be easy with a federate

  20. TiO2/PbS/ZnS heterostructure for panchromatic quantum dot sensitized solar cells synthesized by wet chemical route

    Science.gov (United States)

    Bhat, T. S.; Mali, S. S.; Sheikh, A. D.; Korade, S. D.; Pawar, K. K.; Hong, C. K.; Kim, J. H.; Patil, P. S.

    2017-11-01

    So far we developed the efficient photoelectrodes which can harness the UV as well as the visible regime of the solar spectrum effectively. In order to exploit a maximum portion of solar spectrum, it is necessary to study the synergistic effect of a photoelectrode comprising UV and visible radiations absorbing materials. Present research work highlights the efforts to study the synchronized effect of TiO2 and PbS on the power conversion efficiency of quantum dot sensitized solar cell (QDSSC). A cascade structure of TiO2/PbS/ZnS QDSSC is achieved to enhance the photoconversion efficiency of TiO2/PbS system by incorporating a surface passivation layer of ZnS which avoids the recombination of charge carriers. A QDSSC is fabricated using a simple and cost-effective technique such as hydrothermally grown TiO2 nanorod arrays decorated with PbS and ZnS using successive ionic layer adsorption and reaction (SILAR) method. Synthesized electrode materials are characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FE-SEM), High resolution-transmission electron microscopy (TEM), STEM-EDS mapping, optical and solar cell performances. Phase formation of TiO2, PbS and ZnS get confirmed from the XPS study. FE-SEM images of the photoelectrode show uniform coverage of PbS QDs onto the TiO2 nanorods which increases with increasing number of SILAR cycles. The ZnS layer not only improves the charge transport but also reduces the photocorrosion of lead chalcogenides in the presence of a liquid electrolyte. Finally, the photoelectrochemical (PEC) study is carried out using an optimized photoanode comprising TiO2/PbS/ZnS assembly. Under AM 1.5G illumination the TiO2/PbS/ZnS QDSSC photoelectrode shows 4.08 mA/cm2 short circuit current density in a polysulfide electrolyte which is higher than that of a bare TiO2 nanorod array.

  1. Development of CIGS2 thin film solar cells

    International Nuclear Information System (INIS)

    Dhere, Neelkanth G.; Gade, Vivek S.; Kadam, Ankur A.; Jahagirdar, Anant H.; Kulkarni, Sachin S.; Bet, Sachin M.

    2005-01-01

    Research and development of CuIn 1-x Ga x Se 2-y S y (CIGSS) thin-film solar cells on ultralightweight flexible metallic foil substrates is being carried out at FSEC PV Materials Lab for space applications. Earlier, the substrate size was limited to 3 cm x 2.5 cm. Large-area sputtering systems and scrubber for hydrogen selenide and sulfide have been designed and constructed for preparation of CIGSS thin-films on large (15 cm x 10 cm) substrates. A selenization/sulfurization furnace donated by Shell (formerly Siemens) Solar has also been refurbished and upgraded. The sputtering target assembly design was modified for proper clamping of targets and effective cooling. A new design of the magnetic assembly for large-area magnetron sputtering sources was implemented so as to achieve uniform deposition on large area. Lightweight stainless steel foil and ultralightweight titanium foil substrates were utilized to increase the specific power of solar cells. Sol-gel derived SiO 2 layers were coated on titanium foil by dip coating method. Deposition parameters for the preparation of molybdenum back contact layers were optimized so as to minimize the residual stress as well as reaction with H 2 S. Presently large (15 cm x 10 cm) CuIn 1-x Ga x S 2 (CIGS2) thin film solar cells are being prepared on Mo-coated titanium and stainless steel foil by sulfurization of CuGa/In metallic precursors in diluted Ar:H 2 S(4%). Heterojunction partner CdS layers are deposited by chemical bath deposition. The regeneration sequence of ZnO/ZnO:Al targets was optimized for obtaining consistently good-quality, transparent and conducting ZnO/ZnO:Al bilayer by RF magnetron-sputter deposition. Excellent facilities at FSEC PV Materials Lab are one of its kinds and could serve as a nucleus of a small pilot plant for CIGSS thin film solar cell fabrication

  2. Quantum efficiency as a device-physics interpretation tool for thin-film solar cells

    Science.gov (United States)

    Nagle, Timothy J.

    2007-12-01

    Thin-film solar cells made from CdTe and CIGS p-type absorbers are promising candidates for generating pollution-free electricity. The challenge faced by the thin-film photovoltaics (PV) community is to improve the electrical properties of devices, without straying from low-cost, industry-friendly techniques. This dissertation will focus on the use of quantum-efficiency (QE) measurements to deduce the device physics of thin-film devices, in the hope of improving electrical properties and efficiencies of PV materials. Photons which are absorbed, but not converted into electrical energy can modify the energy bands in the solar cell. Under illumination, photoconductivity in the CdS window layer can result in bands different from those in the dark. QE data presented here was taken under a variety of light-bias conditions. These results suggest that 0.10 sun of white-light bias incident on the CdS layer is usually sufficient to achieve accurate QE results. QE results are described by models based on carrier collection by drift and diffusion, and photon absorption. These models are sensitive to parameters such as carrier mobility and lifetime. Comparing calculated QE curves with experiments, it was determined that electron lifetimes in CdTe are less than 0.1 ns. Lifetime determinations also suggest that copper serves as a recombination center in CdTe. The spatial uniformity of QE results has been investigated with the LBIC apparatus, and several experiments are described which investigate cell uniformity. Electrical variations that occur in solar cells often occur in a nonuniform fashion, and can be detected with the LBIC apparatus. Studies discussed here include investigation of patterned deposition of Cu in back-contacts, the use of high-resistivity TCO layers to mitigate nonuniformity, optical effects, and local shunts. CdTe devices with transparent back contacts were also studied with LBIC, including those that received a strong bromine/dichrol/hydrazine (BDH) etch

  3. Corrosion of copper in oxygen-deficient groundwater with and without deep bedrock micro-organisms: Characterisation of microbial communities and surface processes

    Energy Technology Data Exchange (ETDEWEB)

    Huttunen-Saarivirta, E., E-mail: elina.huttunen-saarivirta@vtt.fi [VTT Technical Research Centre of Finland, Materials Performance, Kemistintie 3, FI-02044 VTT (Finland); Rajala, P. [VTT Technical Research Centre of Finland, Materials Performance, Kemistintie 3, FI-02044 VTT (Finland); Bomberg, M. [VTT Technical Research Centre of Finland, Geobiotechnology, Tietotie 2, FI-02044 VTT (Finland); Carpén, L. [VTT Technical Research Centre of Finland, Materials Performance, Kemistintie 3, FI-02044 VTT (Finland)

    2017-02-28

    Highlights: • Copper was exposed to groundwater with and without deep bedrock micro-organisms. • Biofilm composition was determined and correlated with the behaviour of copper. • Under biotic conditions, the film of Cu{sub 2}S formed on copper surfaces. • Bacterial pool was in a key role for the morphology and properties of Cu{sub 2}S film. • Under abiotic conditions, Cu{sub 2}O systematically developed on copper surfaces. - Abstract: Copper specimens were exposed to oxygen-deficient artificial groundwater in the presence and absence of micro-organisms enriched from the deep bedrock of the planned nuclear waste repository site at Olkiluoto island on the western coast of Finland. During the exposure periods of 4 and 10 months, the copper specimens were subjected to electrochemical measurements. The biofilm developed on the specimens and the water used in the exposures were subjected to microbiological analyses. Changes in the water chemistry were also determined and surfaces of the copper specimens were characterized with respect to the morphology and composition of the formed corrosion products. The results showed that under biotic conditions, redox of the water and open circuit potential (OCP) of the copper specimens were generally negative and resulted in the build-up of a copper sulphide, Cu{sub 2}S, layer due to the activity of sulphate-reducing bacteria (SRB) that were included in the system. In the 4-month test, the electrochemical behaviour of the specimens changed during the exposure and alphaproteobactria Rhizobiales were the dominant bacterial group in the biofilm where the highest corrosion rate was observed. In the 10-month test, however, deltaproteobacteria SRB flourished and the initial electrochemical behaviour and the low corrosion rate of the copper were retained until the end of the test period. Under abiotic conditions, the positive water redox potential and specimen OCP correlated with the formation of copper oxide, Cu{sub 2}O

  4. Quantum dot-dye hybrid systems for energy transfer applications

    Energy Technology Data Exchange (ETDEWEB)

    Ren, Ting

    2010-07-01

    In this thesis, we focus on the preparation of energy transfer-based quantum dot (QD)-dye hybrid systems. Two kinds of QD-dye hybrid systems have been successfully synthesized: QD-silica-dye and QD-dye hybrid systems. In the QD-silica-dye hybrid system, multishell CdSe/CdS/ZnS QDs were adsorbed onto monodisperse Stoeber silica particles with an outer silica shell of thickness 2-24 nm containing organic dye molecules (Texas Red). The thickness of this dye layer has a strong effect on the total sensitized acceptor emission, which is explained by the increase in the number of dye molecules homogeneously distributed within the silica shell, in combination with an enhanced surface adsorption of QDs with increasing dye amount. Our conclusions were underlined by comparison of the experimental results with Monte-Carlo simulations, and by control experiments confirming attractive interactions between QDs and Texas Red freely dissolved in solution. New QD-dye hybrid system consisting of multishell QDs and organic perylene dyes have been synthesized. We developed a versatile approach to assemble extraordinarily stable QD-dye hybrids, which uses dicarboxylate anchors to bind rylene dyes to QD. This system yields a good basis to study the energy transfer between QD and dye because of its simple and compact design: there is no third kind of molecule linking QD and dye; no spacer; and the affinity of the functional group to the QD surface is strong. The FRET signal was measured for these complexes as a function of both dye to QD ratio and center-to-center distance between QD and dye by controlling number of covered ZnS layers. Data showed that fluorescence resonance energy transfer (FRET) was the dominant mechanism of the energy transfer in our QD-dye hybrid system. FRET efficiency can be controlled by not only adjusting the number of dyes on the QD surface or the QD to dye distance, but also properly choosing different dye and QD components. Due to the strong stability, our QD

  5. Forschungszentrum Rossendorf, Institute of Radiochemistry. Annual report 2004

    Energy Technology Data Exchange (ETDEWEB)

    Bernhard, G. (ed.)

    2005-07-01

    The Institute of Radiochemistry (IRC), one of the six Institutes of the Forschungszentrum Rossendorf (FZR) performs basic and applied research in the fields of radiochemistry and radioecology. Motivation and background of our research are environmental processes relevant for the installation of nuclear waste repositories, for remediation of uranium mining and milling sites, and for radioactive contaminations caused by nuclear accidents and fallout. Because of their high radiotoxicity and long half-life the actinides are of special interest. The research is focused on a better understanding of the chemical behavior of actinides in the environment on a molecular level. We will increase our efforts to study both the speciation of actinides on bio-molecular interfaces and their transport in bio-systems. Current topics of our research work are: aquatic chemistry of actinides, actinides in bio-systems, interaction of actinides with solid phases, Reactive transport of actinides. About 60 scientists, technicians and PhD students are employed at the Institute of Radiochemistry. We accomplished many new scientific results in the past year, which are presented in this annual report. Among them only few can be highlighted in this preface. Further progress was achieved in understanding the formation and characterization of uranium containing colloids. The newly installed method of laser-induced breakdown detection was very helpful for the identification of uranium colloids under anoxic conditions. We were very successful in the determination of formation pathways and structure of various actinide complexes. These results contribute to a better understanding of actinide speciation in geo- and bio-systems, especially with respect to the chemical processes on the interfaces. The results achieved in the characterization of the properties, modification, and interaction of the S-layers of Bacillus sphaericus with uranium and some other heavy metals strengthen our hope to use this

  6. Optimization of seed-blanket type fuel assembly for reduced-moderation water reactor

    Energy Technology Data Exchange (ETDEWEB)

    Shelley, Afroza; Shimada, Shoichiro; Kugo, Teruhiko; Okubo, Tsutomu E-mail: okubo@hems.jaeri.go.jp; Iwamura, Takamichi

    2003-10-01

    Parametric studies have been performed for a PWR-type reduced-moderation water reactor (RMWR) with the seed-blanket type fuel assembles to achieve a high conversion ratio, negative void reactivity coefficient and a high burnup by using MOX fuel. From the viewpoint of reactor safety analysis, the fuel temperature coefficients were also studied. From the result of the burnup calculation, it has been seen that ratio of 40-50% of outer blanket in a seed-blanket assembly gives higher conversion ratio compared to the other combination of seed-blanket assembly. And the recommended number of (seed+blanket) layers is 20, in which the number of seed (S) layers is 15 (S15) and blanket (B) layers is 5 (B5). It was found that the conversion ratio of seed-blanket assembly decreases, when they are arranged looks like a flower shape (Hanagara). By the optimization of different parameters, S15B5 fuel assembly with the height of seed of 1000 mmx2, internal blanket of 150 mm and axial blanket of 400 mmx2 is recommended for a reactor of high conversion ratio. In this assembly, the gap of seed fuel rod is 1.0 mm and blanket fuel rod is 0.4 mm. In S15B5 assembly, the conversion ratio is 1.0 and the burnup is 38.18 GWd/t in (seed+internal blanket+outer blanket) region. However, the burnup is 57.45 GWd/t in (seed+internal blanket) region. The cycle length of the core is 16.46 effective full power in month (EFPM) by six batches and the enrichment of fissile Pu is 14.64 wt.%. The void coefficient is +21.82 pcm/%void, however, it is expected that the void coefficient will be negative if the radial neutron leakage is taken into account in the calculation. It is also possible to use S15B5 fuel assembly as a high burnup reactor 45 GWd/t in (seed+internal blanket+outer blanket) region, however, it is necessary to decrease the height of seed to 500 mmx2 to improve the void coefficient. In this reactor, the conversion ratio is 0.97 and void coefficient is +20.81 pcm/%void. The fuel temperature

  7. Gravity, Topography, and Magnetic Field of Mercury from Messenger

    Science.gov (United States)

    Neumann, Gregory A.; Solomon, Sean C.; Zuber, Maria T.; Phillips, Roger J.; Barnouin, Olivier; Ernst, Carolyn; Goosens, Sander; Hauck, Steven A., II; Head, James W., III; Johnson, Catherine L.; hide

    2012-01-01

    On 18 March 2011, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft was inserted into a 12-hour, near-polar orbit around Mercury, with an initial periapsis altitude of 200 km, initial periapse latitude of 60 deg N, and apoapsis at approximately 15,200 km altitude in the southern hemisphere. This orbit has permitted the mapping of regional gravitational structure in the northern hemisphere, and laser altimetry from the MESSENGER spacecraft has yielded a geodetically controlled elevation model for the same hemisphere. The shape of a planet combined with gravity provides fundamental information regarding its internal structure and geologic and thermal evolution. Elevations in the northern hemisphere exhibit a unimodal distribution with a dynamic range of 9.63 km, less than that of the Moon (19.9 km), but consistent with Mercury's higher surface gravitational acceleration. After one Earth-year in orbit, refined models of gravity and topography have revealed several large positive gravity anomalies that coincide with major impact basins. These candidate mascons have anomalies that exceed 100 mGal and indicate substantial crustal thinning and superisostatic uplift of underlying mantle. An additional uncompensated 1000-km-diameter gravity and topographic high at 68 deg N, 33 deg E lies within Mercury's northern volcanic plains. Mercury's northern hemisphere crust is generally thicker at low latitudes than in the polar region. The low-degree gravity field, combined with planetary spin parameters, yields the moment of inertia C/MR2 = 0.353 +/- 0.017, where M=3.30 x 10(exp 23) kg and R=2440 km are Mercury's mass and radius, and a ratio of the moment of inertia of Mercury's solid outer shell to that of the planet of Cm/C = 0.452 +/- 0.035. One proposed model for Mercury's radial density distribution consistent with these results includes silicate crust and mantle layers overlying a dense solid (possibly Fe-S) layer, a liquid Fe

  8. Large-scale, high-performance and cloud-enabled multi-model analytics experiments in the context of the Earth System Grid Federation

    Science.gov (United States)

    Fiore, S.; Płóciennik, M.; Doutriaux, C.; Blanquer, I.; Barbera, R.; Williams, D. N.; Anantharaj, V. G.; Evans, B. J. K.; Salomoni, D.; Aloisio, G.

    2017-12-01

    The increased models resolution in the development of comprehensive Earth System Models is rapidly leading to very large climate simulations output that pose significant scientific data management challenges in terms of data sharing, processing, analysis, visualization, preservation, curation, and archiving.Large scale global experiments for Climate Model Intercomparison Projects (CMIP) have led to the development of the Earth System Grid Federation (ESGF), a federated data infrastructure which has been serving the CMIP5 experiment, providing access to 2PB of data for the IPCC Assessment Reports. In such a context, running a multi-model data analysis experiment is very challenging, as it requires the availability of a large amount of data related to multiple climate models simulations and scientific data management tools for large-scale data analytics. To address these challenges, a case study on climate models intercomparison data analysis has been defined and implemented in the context of the EU H2020 INDIGO-DataCloud project. The case study has been tested and validated on CMIP5 datasets, in the context of a large scale, international testbed involving several ESGF sites (LLNL, ORNL and CMCC), one orchestrator site (PSNC) and one more hosting INDIGO PaaS services (UPV). Additional ESGF sites, such as NCI (Australia) and a couple more in Europe, are also joining the testbed. The added value of the proposed solution is summarized in the following: it implements a server-side paradigm which limits data movement; it relies on a High-Performance Data Analytics (HPDA) stack to address performance; it exploits the INDIGO PaaS layer to support flexible, dynamic and automated deployment of software components; it provides user-friendly web access based on the INDIGO Future Gateway; and finally it integrates, complements and extends the support currently available through ESGF. Overall it provides a new "tool" for climate scientists to run multi-model experiments. At the

  9. A novel approach to imaging extinct seafloor massive sulphides (eSMS) by using ocean bottom seismometer data from the Blue Mining project

    Science.gov (United States)

    Gil, A.; Chidlow, K. L.; Vardy, M. E.; Bialas, J.; Schroeder, H.; Stobbs, I. J.; Gehrmann, R. A. S.; North, L. J.; Minshull, T. A.; Petersen, S.; Murton, B. J.

    2017-12-01

    Seafloor massive sulphide (SMS) deposits have generated great interest regarding their formation and composition, since their discovery in 1977. SMS deposits form through hydrothermal circulation and are therefore commonly found near hydrothermal vent sites. The high base (Cu, Zn) and precious metal (Au, Ag) content has interested mining companies, due to their potentially high economic value. Currently, the possibility of mining extinct seafloor massive sulphides (eSMS) deposits has opened a debate about their environmentally and economically sustainable exploitation. A major goal is the rapid exploration and assessment of deposit structure and volume. This is challenging due to their small dimensions (100s m diameter) and typically great water depths (> 3000 mbsl). Here we present a novel approach combining seismic reflection/refraction forward modelling to data acquired from the TAG hydrothermal field (26ºN, Mid-Atlantic Ridge, 3500mbsl) to image deep-water eSMS deposits. In May 2016, the RV METEOR shot 30, short (<10km) MSC profiles across the TAG area. The data were recorded on a dense cluster (<75 m apart) of ocean bottom seismometers (OBS) and were able to image the subsurface of several 300m diameter eSMS deposits. The results show that the eSMS deposits present high velocities (5.4-6.6 km/s) to depths 200m below the seafloor where they are hosted in a 500m thick low-velocity (3.0-3.7 km/s) layer of altered basalt. In contrast to active hydrothermal systems, we see no evidence in the eSMS of a low-velocity anhydrite layer. The velocity-depth models obtained from this innovative method have been combined with other methods to study these eSMS deposits, such as electromagnetics, rocks physics and drilling technics, and the results are shown to concur, yielding information about deposit structure at depth. For example, the high-velocity layer extends deeper than the conductive layer, indicating a deep stock work of low-connectivity sulphides beneath a main

  10. Ultrastructural changes in biofilm forms of staphylococci cultivated in a mixed culture with lactobacilli

    Directory of Open Access Journals (Sweden)

    G. Lavryk

    2017-02-01

    Full Text Available The capacity of opportunistic bacteria for biofilm formation plays an important role in the development of chronic inflammatory processes, which are difficult to treat. To improve antimicrobial therapy methods, the influence of lactobacilli on the ultrastructure of biofilm-forming clinical strains of staphylococci when co-cultured was investigated. 5 biofilm-forming clinical strains of S. aureus from the skin of acne vulgaris patients (n = 24 were isolated. Using transmission electron microscopy (TEM the morphological changes of S. aureus cells in the mixed culture with standard strains of Lactobacillus plantarum 8P-A3 and clinical strains of L. fermentum (n = 4 were studied. It was found that in 48 hours after the inoculation on the medium of samples of mixed cultures of L. plantarum 8P-A3 and S. aureus growth of staphylococci was not revealed. Only in some cases of mixed cultures of L. fermentum and biofilm-forming staphylococci was growth of S. aureus obtained. In electron diffraction patterns of control samples of 24-hour staphylococcal monocultures and 48-hour lactobacilli monocultures, natural development of the population at the cellular level was observed. Destructive changes under the influence of lactobacilli (probiotic and clinical strains were detected in all ultrathin sections of the cells of biofilm-forming and planktonic staphylococci. Significant destructive changes in the cell wall of the staphylococci were observed: thickening, obtaining of irregular form, detachment of the cytoplasmic membrane, the complete destruction of the peptidoglycan layer and the emergence of "shadow cells". On all electron diffraction patterns fibrillar-threadlike structures of DNA could not be observed, but in some cases mesosome-like formations were poorly contrasted. It was established that the surface S-layer of lactobacilli was expressed on a significantly larger scale in the mixed culture with staphylococci. In mixed culture of clinical strains

  11. An experimental study on the preparation of tochilinite-originated intercalation compounds comprised of Fe 1-xS host layers and various kinds of guest layers

    Science.gov (United States)

    Peng, Yiya; Xi, Guangcheng; Zhong, Chang; Wang, Linping; Lu, Jun; Sun, Ximeng; Zhu, Lu; Han, Qikun; Chen, Lin; Shi, Lei; Sun, Mei; Li, Qianrong; Yu, Min; Yin, Mingwen

    2009-08-01

    Tochilinite represents a mineral group of ordered mixed-layer structures containing alternating Fe 1-xS layers with mackinawite-like structure and metal hydroxide layers with Mg(OH) 2-like structure. In this article, we report the preparation of a series of tochilinite-originated (or Fe 1-xS-based) intercalation compounds (ICs). According to their preparation procedures, these ICs can be divided into four kinds. The first kind of IC was sodium tochilinite (Na-tochilinite), which was prepared by the hydrothermal reaction of metallic Fe particles with concentrated Na 2S·9H 2O aqueous solutions. The hydroxide layer of the Na-tochilinite was a mixed hydroxide of Na + ions along with a certain amount of Fe 2+ ions. When the hydroxide layer of the Na-tochilinite completely dissolved in aqueous solutions, a Fe-deficient mackinawite-like phase Fe 1-xS was obtained, which was probably an electron-deficient p-type conductor. The second kind of ICs was prepared by 'low-temperature direct intercalation in aqueous solutions, using Na-tochilinite as a parental precursor. When the Na-tochilinite was ultrasonicated in aqueous solutions containing Lewis basic complexing agents (like NH 3, N 2H 4, 2,2'-bipyridine (bipy), and 1,10-phenanthroline (phen)), the Na + ions of the Na-tochilinite were removed and the Lewis basic complexing agents entered the hydroxide layer of the Na-tochilinite and became coordinated with the Fe 2+ ions, and the second kind of ICs was thus produced. The second kind of ICs includes NH 3 IC, N 2H 4 IC, N 2H 4-NH 3 IC, [Fe(bipy) 3] 2+-containing IC and [Fe(phen) 3] 2+-containing IC. The third kind of ICs, which includes NH 3 IC, N 2H 4-NH 3 IC and N 2H 4-LiOH (NaOH) IC, was prepared by the hydrothermal reaction of metallic Fe particles with (NH 4) 2S aqueous solution, S (elemental) + N 2H 4·H 2O aqueous solution, and S + N 2H 4·H 2O + LiOH (NaOH) aqueous solution, respectively. The third kind of ICs has a close relationship with the second kind of ICs both

  12. Charge carrier transport in Cu(In,Ga)Se2 thin-film solar-cells studied by electron beam induced current and temperature and illumination dependent current voltage analysis

    International Nuclear Information System (INIS)

    Nichterwitz, Melanie

    2012-01-01

    This work contributes to the understanding of generation dependent charge-carrier transport properties in Cu(In,Ga)Se 2 (CIGSe)/ CdS/ ZnO solar cells and a consistent model for the electronic band diagram of the heterojunction region of the device is developed. Cross section electron-beam induced current (EBIC) and temperature and illumination dependent current voltage (IV) measurements are performed on CIGSe solar cells with varying absorber layer compositions and CdS thickness. For a better understanding of possibilities and limitations of EBIC measurements applied on CIGSe solar cells, detailed numerical simulations of cross section EBIC profiles for varying electron beam and solar cell parameters are performed and compared to profiles obtained from an analytical description. Especially the effects of high injection conditions are considered. Even though the collection function of the solar cell is not independent of the generation function of the electron beam, the local electron diffusion length in CIGSe can still be extracted. Grain specific values ranging from (480±70) nm to (2.3±0.2) μm are determined for a CuInSe 2 absorber layer and a value of (2.8±0.3) μm for CIGSe with a Ga-content of 0.3. There are several models discussed in literature to explain generation dependent charge carrier transport, all assuming a high acceptor density either located in the CIGSe layer close to the CIGSe/CdS interface (p + layer), within the CdS layer or at the CdS/ZnO interface. In all models, a change in charge carrier collection properties is caused by a generation dependent occupation probability of the acceptor type defect state and the resulting potential distribution throughout the device. Numerical simulations of EBIC and IV data are performed with parameters according to these models. The model that explains the experimental data best is that of a p + layer at the CIGSe/CdS interface and acceptor type defect states at the CdS/ZnO interface. The p + layer leads

  13. The role of Cd and Ga in the Cu(In,Ga)S2/CdS heterojunction studied with X-ray spectroscopic methods

    International Nuclear Information System (INIS)

    Johnson, Benjamin E.

    2010-01-01

    readily dissolved by HCl. Also, because it is thought that Cd will replace the cations in the CIS lattice, most likely Cu, the resulting Cd-S bonds in CIS:Cd will be different from those in CdS. Further experiments could not exclude the possibility that Cd diffuses into the CIS. However, it was shown that Cu from the absorber diffuses into the buffer layer during junction formation, although the Cu does not reach the surface of a full ∝35 nm thick CdS layer. The valence band offset between Cu(In,Ga)S 2 and CdS was independent of Ga concentration and had a value 1.35 eV±0.20 eV. However, the position of the conduction band did show a dependence on Ga and moved to lower binding energies with increasing Ga concentration. ∝8% Ga on the absorber surface opened the Cu(In,Ga)S 2 band gap by ∝150 meV when compared to CuInS 2 . Although the opening of the band gap exacerbates the conduction band offset in the CIS/CdS junction, the inclusion of Ga increases the open circuit voltage of the solar cell by ∝100 mV. (orig.)

  14. BN-350 unattended safeguards system current status and initial fuel movement data

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Richard Brady [Los Alamos National Laboratory; Browne, Michael C [Los Alamos National Laboratory; Parker, Robert F [Los Alamos National Laboratory; Ingegneri, Maurizio [IAEA

    2009-01-01

    The Unattended and Remote Monitoring (UNARM) system at the BN-350 fast breeder reactor facility in Aktau, Kazakhstan continues to provide safeguards monitoring data as the spent fuel disposition project transitions from wet fuel storage to dry storage casks. Qualitative data from the initial cask loading procedures has been released by the International Atomic Energy Agency (IAEA) and is presented here for the first time. The BN-350 fast breeder reactor in Aktau, Kazakhstan, operated as a plutonium-producing facility from 1973 W1til 1999. Kazakhstan signed the Nonproliferation Treaty (NPT) in February 1994, and shortly afterwards the IAEA began safeguarding the reactor facility and its nuclear material. Slnce the cessation of reactor operations ten years ago, the chief proliferation concern has been the spent fuel assemblies stored in the pond on-site. By 2002, all fuel assemblies in wet storage had been repackaged into proliferation-resistant canisters. From the beginning, the IAEA's safeguards campaign at the BN-350 included a constant unattended sensor presence in the form of UNARM which monitors nuclear material activities at the facility in the absence of inspector presence. The UNARM equipment at the BN-350 was designed to be modular and extensible, allowing the system to adapt as the safeguards requirements change. This has been particularly important at the BN-350 due to the prolonged wet storage phase of the project. The primary function of the BN-350 UNARM system is to provide the IAEA with an independent, radiation-centric Containment and Surveillance (C&S) layer in addition to the standard seals and video systems. The UNARM system has provided continuous Continuity of Knowledge (COK) data for the BN-350's nuclear material storage areas in order to ensure the validity of the attended measurements during the lifetime of the project. The first of these attended measurements was characterization of the spent fuel assemblies. This characterization

  15. Cellular responses in Bacillus thuringiensis CS33 during bacteriophage BtCS33 infection.

    Science.gov (United States)

    Wu, Dandan; Yuan, Yihui; Liu, Pengming; Wu, Yan; Gao, Meiying

    2014-04-14

    Bacillus thuringiensis (Bt) has been widely used for 50years as a biopesticide for controlling insect pests. However, bacteriophage infection can cause failures in 50%-80% of the batches during Bt fermentation, resulting in severe losses. In the present work, the physiological and biochemical impacts of Bt strain CS33 have been studied during bacteriophage infection. This study adopted a gel-based proteomics approach to probe the sequential changed proteins in phage-infected Bt cells. To phage, it depressed the host energy metabolism by suppressing the respiration chain, the TCA cycle, and the utilization of PHB on one hand; on the other hand, it hijacked the host translational machine for its own macromolecular synthesis. To host, superinfection exclusion might be triggered by the changes of S-layer protein and flagella related proteins, which were located on the cell surface and might play as the candidates for the phage recognition. More importantly, the growth rate, cell mass, and ICPs yield were significantly decreased. The low yield of ICPs was mainly due to the suppressed utilization of PHB granules. Further functional study on these altered proteins may lead to a better understanding of the pathogenic mechanisms and the identification of new targets for phage control. B. thuringiensis (Bt) has been widely used for 50years as a safe biopesticide for controlling agricultural and sanitary insect pests. However, bacteriophage infection can cause severe losses during B. thuringiensis fermentation. The processes and consequences of interactions between bacteriophage and Bt were still poorly understood, and the molecular mechanisms involved were more unknown. This study adopted a gel-based proteomics approach to probe the physiological and biochemical impacts of Bt strain CS33 after phage-infection. The interactions between phage BtCS33 and its host Bt strain CS33 occurred mainly on four aspects. First, phage synthesized its nucleic acids through metabolic

  16. The role of Cd and Ga in the Cu(In,Ga)S{sub 2}/CdS heterojunction studied with X-ray spectroscopic methods

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Benjamin E.

    2010-08-15

    be CdS as this is readily dissolved by HCl. Also, because it is thought that Cd will replace the cations in the CIS lattice, most likely Cu, the resulting Cd-S bonds in CIS:Cd will be different from those in CdS. Further experiments could not exclude the possibility that Cd diffuses into the CIS. However, it was shown that Cu from the absorber diffuses into the buffer layer during junction formation, although the Cu does not reach the surface of a full {proportional_to}35 nm thick CdS layer. The valence band offset between Cu(In,Ga)S{sub 2} and CdS was independent of Ga concentration and had a value 1.35 eV{+-}0.20 eV. However, the position of the conduction band did show a dependence on Ga and moved to lower binding energies with increasing Ga concentration. {proportional_to}8% Ga on the absorber surface opened the Cu(In,Ga)S{sub 2} band gap by {proportional_to} 150 meV when compared to CuInS{sub 2}. Although the opening of the band gap exacerbates the conduction band offset in the CIS/CdS junction, the inclusion of Ga increases the open circuit voltage of the solar cell by {proportional_to}100 mV. (orig.)

  17. Charge separation in contact systems with CdSe quantum dot layers

    International Nuclear Information System (INIS)

    Zillner, Elisabeth Franziska

    2013-01-01

    (recombination). The values of QD-ITO distance and trap density, determined with the simulation were consistent with transmission electron microscopy and photoluminescence measurements. The separation and diffusion of charge carriers was limited due to trapping of charge carriers. Smaller interparticle distances led to faster decays in CdSe QD monolayers. However the increase of traps, which resulted in a slower decay dominated and led to longer decay times of SPV transients of modified CdSe QD layers. By deposition of CdSe QDs on CdS a heterojunction was created. The CdS layer served as acceptor for electrons excited in CdSe QDs. Furthermore a CdSe QD/CdTe nanoparticle heterojunction was realized by successive electrophoretic deposition. CdSe QDs acted as electron acceptors, whereas CdTe nanoparticles acted as electron donors. Charge separation was dominated by the CdSe QD/CdTe nanoparticle interphase, as inverted layer stacking of CdSe QDs and CdTe nanoparticles gave an inverted SPV signal.

  18. Effect of the interface on UV–vis–IR photodetection performance of PbS/ZnO nanocomposite photocatalysts

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Jie; Li, Yuanzhi; Yang, Yi; Bai, Jilin; Zhao, Xiujian

    2015-12-15

    Graphical abstract: - Highlights: • We prepare two PbS/ZnO nanocomposite photocatalyts with different interface. • The PbS/ZnO interface plays important role in UV–vis–IR photodetection performance. • Disordered ZnS layer between PbS and ZnO considerably decreases photocurrent. • We reveal the origin of the interface effect on photodetection. - Abstract: Two PbS/ZnO nanocomposites with the same Pb/Zn molar ratio of 1:12 and different PbS/ZnO interface were prepared by depositing PbS nanocrystals on nano ZnO with the reaction between Pb(NO{sub 3}){sub 2} and Na{sub 2}S through changing the sequence of adding Pb(NO{sub 3}){sub 2} and Na{sub 2}S to the nano ZnO suspension: (A) first adding Pb(NO{sub 3}){sub 2} followed by adding Na{sub 2}S (denoted PbS/ZnO-A); (B) first adding Na{sub 2}S followed by adding Pb(NO{sub 3}){sub 2} (denoted PbS/ZnO-B). The PbS/ZnO nanocomposites are characterized by XRD, BET, Raman, TEM, XPS, and UV–vis–IR. The characterizations indicate that PbS/ZnO-A has an interface of PbS nanocrystal closely contacted to ZnO nanocrystal while PbS/ZnO-B has an interface of a disordered layer between PbS nanocrystal and ZnO nanocrystal. It is found for the first time that the PbS/ZnO interface plays an important role in their photodetection performance. PbS/ZnO-A exhibits much higher photoresponse current and lower rise and recovery time than both PbS/ZnO-B and a mixture of nano PbS and ZnO with the same Pb/Zn molar ratio as PbS/ZnO-A for visible and near-infrared photodetection. PL and the impedance measurement in dark and irradiation reveal that the superior photodetection performance of PbS/ZnO-A over PbS/ZnO-B is attributed to its lower e–h recombination and migration resistance under the irradiation of visible and infrared light due to its very good PbS/ZnO interface of PbS nanocrystals closely attached ZnO nanocrystals, through which photogenerated electrons inject efficiently from the conduction band of PbS to that of ZnO. In

  19. Seismological structures of the subducted Philippine Sea plate and the overriding SW Japan arc, - Reinterpretation of the wide-angle reflection data in the Kii Peninsula, SW Japan -

    Science.gov (United States)

    Iwasaki, Takaya; Kurashimo, Eiji; Abe, Susumu; Yokota, Ken; Iidaka, Takashi; Katao, Hiroshi; Higashinaka, Motonori; Nakanishi, Ayako; Kaneda, Yoshiyuki

    2017-04-01

    dipping reflector band just south of the MTL. This reflection band, about 10-15 km thick, includes the SMB, extending from 2-10 km to 25-35 km depth. The MTL itself is recognized as the uppermost part of this band inclining northward to a depth of nearly 25 km. In the reflection processing, the PHS plate is well imaged as northward dipping reflectors in a depth range of 20-35 km beneath the southern half of our profile. According to the wide-angle reflection analysis, a thin (less than 1 km) low velocity (3.5 5km/s) layer is situated at the top of the PHS plate under the southernmost part of the profile, which corresponds to the trenchward half of the conditionally stable zone. In the central part of the profile (the landward half of the conditionally stable zone), strong reflectors with 2-3 km/s velocity contrast are distributed in a diffused manner at 30-35 km depths, around which low frequency earthquakes are occurring. Such reflective signature fades out further north in the region of stable regime. The obtained lateral structural change are clearly correlated with the frictional properties of the plate boundary, probably controlled by dehydrated fluids from the subducted PHS plate.

  20. Acoustic Streaming, The “Small Invention” of Cianobacteria?

    Directory of Open Access Journals (Sweden)

    Koiller, Jair

    2010-12-01

    Full Text Available Micro-engineering pumping devices without mechanical parts appeared “way back” in the early 1990’s. The working principle is acoustic streaming. Has Nature “rediscovered” this invention 2.7 Gyr ago? Strands of marine cyanobacteria Synechococcus swim 25 diameters per second without any visible means of propulsion. We show that nanoscale amplitude vibrations on the S-layer (a crystalline shell outside the outer membrane present in motile strands and frequencies of the order of 0.5-1.5 MHz (achievable by molecular motors, could produce steady streaming slip velocities outside a (Stokes boundary layer. Inside this boundary layer the flow pattern is rotational (hence biologically advantageous. In addition to this purported “swimming by singing”, we also indicate other possible instantiations of acoustic streaming. Sir James Lighthill has proposed that acoustic streaming occurs in the cochlear dynamics, and new findings on the outer hair cell membranes are suggestive. Other possibilities are membrane vibrations of yeast cells, enhancing its chemistry (beer and bread, keep it up, yeast!, squirming motion of red blood cells along capillaries, and fluid pumping by silicated diatoms.

    Los mecanismos de bombeo en microingeniería aparecieron al principio de la década de los 90. El principio detrás de esto es el de flujo acústico. ¿Ha descubierto la Naturaleza este invento de hace 2.700 millones de años? Algunas cianobacterias marinas de la especie Synechococcus nadan 25 diámetros por segundo sin ningún medio visible de propulsión. Especulamos en este artículo que vibraciones de amplitud de nanoescala del estrato S (una cáscara cristalina que cubre las membranas exteriores en las cepas móviles y con frecuencias del orden de 0,5-1,5 MHz (y esto es factible por los motores moleculares, podrían producir velocidades de deslizamiento del fluido, en el exterior de la frontera de la región Stokes. Dentro de esta capa límite (que

  1. Charge separation in contact systems with CdSe quantum dot layers

    Energy Technology Data Exchange (ETDEWEB)

    Zillner, Elisabeth Franziska

    2013-03-06

    (recombination). The values of QD-ITO distance and trap density, determined with the simulation were consistent with transmission electron microscopy and photoluminescence measurements. The separation and diffusion of charge carriers was limited due to trapping of charge carriers. Smaller interparticle distances led to faster decays in CdSe QD monolayers. However the increase of traps, which resulted in a slower decay dominated and led to longer decay times of SPV transients of modified CdSe QD layers. By deposition of CdSe QDs on CdS a heterojunction was created. The CdS layer served as acceptor for electrons excited in CdSe QDs. Furthermore a CdSe QD/CdTe nanoparticle heterojunction was realized by successive electrophoretic deposition. CdSe QDs acted as electron acceptors, whereas CdTe nanoparticles acted as electron donors. Charge separation was dominated by the CdSe QD/CdTe nanoparticle interphase, as inverted layer stacking of CdSe QDs and CdTe nanoparticles gave an inverted SPV signal.

  2. Research and development of CdTe based thin film PV solar cells

    Science.gov (United States)

    Diso, Dahiru Garba

    -time of 2-3 days. Further work should be carried out to increase the life-time of this bath, so that there can be used continuously minimising waste solution production in a manufacturing line.An efficiencies showing up to 7% was achieved for complete devices. However, the consistency and reproducibility remains un-resolved due to production of efficiencies between (2 - 7)% efficient devices varying from batch to batch. One of the reasons has been identified as the growth of CdS nano-rods with spacing between them. This is the first observation of CdS nano-rods and could open up many applications in nanodevices area. In order to improve the consistency of the solar cell efficiency, CdS layers should be grown with nano-rods aligned perpendicular to the glass surface and with tight packing without gaps, or with uniform coverage of CdS over the conducting glass surface.The possibility of growth of CdTe absorber layers with n- and p-type electrical conduction using change of stoichiometry was confirmed using the results presented in this thesis. This is a key finding, important to form multi-layer solar cell structures in the future.

  3. Bacillus anthracis: una mirada molecular a un patógeno célebre Bacillus anthracis: a molecular look at a famous pathogen

    Directory of Open Access Journals (Sweden)

    María E Pavan

    2011-12-01

    molecular aspects of traditional virulence factors: capsule, protective antigen, lethal factor and edema factor are described in depth, together with virulence factors recently proposed, such as the siderophores petrobactin and bacillibactin, the S-layer adhesin and the MntA lipoprotein. It is detailed the molecular organization of megaplasmids pXO1 and pXO2, including the pathogenicity island of pXO1. The genetic skeleton of these plasmids has been observed in related species, and this could be attributed to lateral gene transfer. Finally, the two anthrax toxin protective antigen receptors, ANTXR1/TEM8 and ANTXR2/CMG2, essential for the interaction of the pathogen with the host, are presented. The molecular studies performed in recent years have greatly increased knowledge in different aspects of this microorganism and its relationship with the host, but at the same time they have raised new questions about this noted pathogen.

  4. Optical dynamics of MgO/Ga{sub 4}Se{sub 3}S interface

    Energy Technology Data Exchange (ETDEWEB)

    Qasrawi, A.F., E-mail: aqasrawi@aauj.edu [Department of Physics, Arab-American University, Jenin, West Bank, Palestine (Country Unknown); Group of Physics, Faculty of Engineering, Atilim University, 06836 Ankara (Turkey); Abd-Alrazq, Mariam M. [Department of Physics, Arab-American University, Jenin, West Bank, Palestine (Country Unknown); Gasanly, N.M. [Department of Physics, Middle East Technical University, 06531 Ankara (Turkey)

    2014-01-15

    Highlights: • A p–n interface made of MgO as an optical window to Ga{sub 4}Se{sub 3}S crystals is designed. • The device is studied by means of transmittance, reflectance and absorbance. • The reflection dependence on incident angle is investigated in the range of 30–80°. • The Brewster angles for the layers are determined. • The strong absorption domination conditions are reported. -- Abstract: A new p–n interface made of p-type MgO as an optical window to the n-type Ga{sub 4}Se{sub 3}S crystals is investigated by means of optical reflectance, transmittance and absorbance in the incident light wavelength (λ) range of 200–1100 nm. The reflectivity spectral analysis as a function of angle of incidence for MgO, Ga{sub 4}Se{sub 3}S and the Ga{sub 4}Se{sub 3}S/MgO layers revealed Brewster angles of 75°, 80° and 70° with the corresponding dielectric constants of 13.93, 32.16 and ε{sub MgO}=7.55ε{sub Ga{sub 4Se{sub 3S}}}, respectively. To remove Brewster condition of reflection and obtain maximum absorption, the light must be incident from the MgO side. A novel light absorbability is observed. Namely, for all λ < 600 nm, the absorbance is dominated by the Ga{sub 4}Se{sub 3}S layer. For larger λ values, while the crystal absorbance decreases significantly, the bilayer absorbance increased by four times in the visible range and three times in the IR range of spectrum. In the MgO layer, two distinct sets of band tails of the localized states with the widths of 2.30 and 1.26 eV are determined from the absorption spectral analysis. These band tails shift up to 2.32 and 1.44 eV when the interface is constructed. In addition, an indirect energy band gaps (E{sub g}) which are located at 3.10, 2.13 and 1.90 eV for the MgO, Ga{sub 4}Se{sub 3}S and the Ga{sub 4}Se{sub 3}S/MgO layers, respectively, are determined. The E{sub g} value of the crystal shifts by a 0.23 eV upon bilayer construction. The reflection properties, the band tails, the energy gaps and