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Sample records for magnetospirillum magneticum amb1

  1. Metamorphosis of Magnetospirillum magneticum AMB-1 cells

    Institute of Scientific and Technical Information of China (English)

    张风丽; 张葵; 赵三军; 肖天; Michel; DENIS; 吴龙飞

    2010-01-01

    Magnetospirillum magneticum strain AMB-1 belongs to the family of magnetotactic bacteria. It possesses a magnetosome chain aligning, with the assistance of cytoskeleton filaments MamK, along the long axis of the spiral cells. Most fresh M. magneticum AMB-1 cells exhibit spiral morphology. In addition, other cell shapes such as curved and spherical were also observed in this organism. Interestingly, the spherical cell shape increased steadily with prolonged incubation time. As the actin-like cytoskeleton pro...

  2. Redox control of iron biomineralization in Magnetospirillum magneticum AMB-1

    Science.gov (United States)

    Jones, Stephanie Rhianon

    Magnetotactic bacteria have evolved complex subcellular machinery to construct linear chains of magnetite nanocrystals that allow the host cell to sense direction. Each mixed-valent iron nanoparticle is mineralized from soluble iron within a membrane-encapsulated vesicle termed the magnetosome, which serves as a specialized compartment that regulates the iron, redox, and pH environment of the growing mineral. In order to dissect the biological components that control this process, we have carried out genetic and biochemical studies of proteins proposed to function in iron mineralization in Magnetospirillum magneticum AMB-1. As iron biomineralization by magnetotactic bacteria represents a particularly interesting case for understanding how the production of nanomaterials can be programmed at the genetic level, we also apply synthetic biology techniques towards the production of new cellular materials and new cellular functions. As the production of magnetite requires both the formation of Fe(II) and Fe(III), the redox components of the magnetosome play an essential role in this process. Using genetic complementation studies, we show that the redox cofactors or heme sites of the two putative redox partners, MamP and MamT, are required for magnetite biomineralization in vivo and that removal of one or both sites leads to defects in mineralization. We develop and optimize a heterologous expression method in the E. coli periplasm to cleanly isolate fully heme-loaded MamP for biochemical studies. Spectrochemical redox titrations show that the reduction potential of MamP lies in a different range than other c-type cytochrome involved in either Fe(III) reduction or Fe(II) oxidation. Nonetheless, in vitro mineralization studies with MamP and Fe(II) show that it is able to catalyze the formation of mixed-valent Fe(II)/Fe(III) oxides such as green rust. Biomineralization also requires lattice-templating proteins that guide the growth of the functional crystalline material. We

  3. Involvement of a Gene Encoding Putative Acetate Kinase in Magnetosome Synthesis in Magnetospirillum magneticum AMB-1

    Directory of Open Access Journals (Sweden)

    ARIS TRI WAHYUDI

    2006-03-01

    Full Text Available A nonmagnetic mutant of Magnetospirillum magneticum AMB-1, designated NMA40, was constructed by mini-Tn5 transposon mutagenesis to identify genes involved in magnetosome synthesis. Transposon delivery was carried out through conjugation between M. magneticum AMB-1 as a recipient and Escherichia coli S17-1 (λ pir carrying pUTmini-Tn5Km1 as a donor strain. NAM40 did not respond to the magnetic fields and completely lacked of magnetosome in the cell. DNA sequence/gen interrupted by transposon (called flanking DNA was isolated by inverse PCR and cloned into pGEM-T Easy. Alignment of the DNA sequence of the flanking DNA allowed the isolation of an open reading frame (ORF2 within an operon consisting of three genes. The amino acid sequence deduced from ORF2 showed homology with acetate kinase from Sinorhizobium meliloti (50% identity and 67% similarity, which function for acetate metabolism. Further analysis revealed that upstream of ORF2 is ORF1, had homology with phosphotransacetylase of S. meliloti (67% identity, 77% similarity, and ORF3 located downstream of ORF2, had homology with hypothetical protein of Thermotoga maritima (30% identity, 60% similarity. ORF2 was subsequently isolated, cloned, and overexpressed in Escherichia coli BL21 (DE3 pLysS as an ORF2-Histag fusion polypeptide.

  4. Changes of cell growth and magnetosome biomineralization in Magnetospirillum magneticum AMB-1 after ultraviolet-B irradiation

    Directory of Open Access Journals (Sweden)

    Yinzhao eWang

    2013-12-01

    Full Text Available Effects of ultraviolet radiation on microorganisms are of great interest in field of microbiology and planetary sciences. In the present study, we used Magnetospirillum magneticum AMB-1 as a model organism to examine the influence of ultraviolet-B (UV-B radiation on cell growth and magnetite biomineralization of magnetotactic bacteria. Live AMB-1 cells were exposed to UV-B radiation for 60 s, 300 s and 900 s, which correspond to radiation doses of 120 J/m2, 600 J/m2 and 1800 J/m2, respectively. After irradiation, the amounts of cyclobutane pyrimidine dimers and reactive oxygen species of the cells were increased, and cell growth was stunted up to ~170 h, depending on the UV-B radiation doses. The UV-B irradiated cells also produced on average more magnetite crystals with larger grain sizes and longer chains, which results in changes of their magnetic properties.

  5. Magnetosomes extracted from Magnetospirillum magneticum strain AMB-1 showed enhanced peroxidase-like activity under visible-light irradiation.

    Science.gov (United States)

    Li, Kefeng; Chen, Chuanfang; Chen, Changyou; Wang, Yuzhan; Wei, Zhao; Pan, Weidong; Song, Tao

    2015-05-01

    Magnetosomes are intracellular structures produced by magnetotactic bacteria and are magnetic nanoparticles surrounded by a lipid bilayer membrane. Magnetosomes reportedly possess intrinsic enzyme mimetic activity similar to that found in horseradish peroxidase (HRP) and can scavenge reactive oxygen species depending on peroxidase activity. Our previous study has demonstrated the phototaxis characteristics of Magnetospirillum magneticum strain AMB-1 cells, but the mechanism is not well understood. Therefore, we studied the relationship between visible-light irradiation and peroxidase-like activity of magnetosomes extracted from M. magneticum strain AMB-1. We then compared this characteristic with that of HRP, iron ions, and naked magnetosomes using 3,3',5,5'-tetramethylbenzidine as a peroxidase substrate in the presence of H2O2. Results showed that HRP and iron ions had different activities from those of magnetosomes and naked magnetosomes when exposed to visible-light irradiation. Magnetosomes and naked magnetosomes had enhanced peroxidase-like activities under visible-light irradiation, but magnetosomes showed less affinity toward substrates than naked magnetosomes under visible-light irradiation. These results suggested that the peroxidase-like activity of magnetosomes may follow an ordered ternary mechanism rather than a ping-pong mechanism. This finding may provide new insight into the function of magnetosomes in the phototaxis in magnetotactic bacteria.

  6. A second actin-like MamK protein in Magnetospirillum magneticum AMB-1 encoded outside the genomic magnetosome island.

    Directory of Open Access Journals (Sweden)

    Jean-Baptiste Rioux

    Full Text Available Magnetotactic bacteria are able to swim navigating along geomagnetic field lines. They synthesize ferromagnetic nanocrystals that are embedded in cytoplasmic membrane invaginations forming magnetosomes. Regularly aligned in the cytoplasm along cytoskeleton filaments, the magnetosome chain effectively forms a compass needle bestowing on bacteria their magnetotactic behaviour. A large genomic island, conserved among magnetotactic bacteria, contains the genes potentially involved in magnetosome formation. One of the genes, mamK has been described as encoding a prokaryotic actin-like protein which when it polymerizes forms in the cytoplasm filamentous structures that provide the scaffold for magnetosome alignment. Here, we have identified a series of genes highly similar to the mam genes in the genome of Magnetospirillum magneticum AMB-1. The newly annotated genes are clustered in a genomic islet distinct and distant from the known magnetosome genomic island and most probably acquired by lateral gene transfer rather than duplication. We focused on a mamK-like gene whose product shares 54.5% identity with the actin-like MamK. Filament bundles of polymerized MamK-like protein were observed in vitro with electron microscopy and in vivo in E. coli cells expressing MamK-like-Venus fusions by fluorescence microscopy. In addition, we demonstrate that mamK-like is transcribed in AMB-1 wild-type and DeltamamK mutant cells and that the actin-like filamentous structures observed in the DeltamamK strain are probably MamK-like polymers. Thus MamK-like is a new member of the prokaryotic actin-like family. This is the first evidence of a functional mam gene encoded outside the magnetosome genomic island.

  7. Magnetosome formation and expression of mamA, mms13, mms6 and magA in Magnetospirillum magneticum AMB-1 exposed to pulsed magnetic field.

    Science.gov (United States)

    Wang, Xiaoke; Liang, Likun; Song, Tao; Wu, Longfei

    2009-09-01

    To investigate the effects of pulsed magnetic field on magnetosome formation in Magnetospirillum magneticum AMB-1, cultures inoculated with either mangetic or non-magnetic pre-cultures were incubated under 1 mT pulsed magnetic field. Magnetism of cells was measured by using spectrophotometer coupled with applied magnetic fields and the values were described as C(mag). Magnetosome in cells was counted by transmission electron microscopy observation. The results showed that pulsed magnetic field did not affect cellular growth, but enhanced magnetosome formation. The applied pulsed magnetic field might exceed the chain of magnetosomes and change the homogeneity of the magnetosome particles. The results implied that magnetite precipitation induced by the adjacent magnetosome was affected by pulsed magnetic field. Moreover, the applied pulsed magnetic field up-regulated the magA and mamA expression in cells, which might account for the increasing number and the exceeding chain of magnetosomes in cells.

  8. Effects of static magnetic field on magnetosome formation and expression of mamA, mms13, mms6 and magA in Magnetospirillum magneticum AMB-1.

    Science.gov (United States)

    Wang, Xiaoke; Liang, Likun

    2009-05-01

    Magnetotactic bacteria produce nanometer-size intracellular magnetic crystals. The superior crystalline and magnetic properties of magnetosomes have been attracting much interest in medical applications. To investigate effects of intense static magnetic field on magnetosome formation in Magnetospirillum magneticum AMB-1, cultures inoculated with either magnetic or non-magnetic pre-cultures were incubated under 0.2 T static magnetic field or geomagnetic field. The results showed that static magnetic field could impair the cellular growth and raise C(mag) values of the cultures, which means that the percentage of magnetosome-containing bacteria was increased. Static magnetic field exposure also caused an increased number of magnetic particles per cell, which could contribute to the increased cellular magnetism. The iron depletion in medium was slightly increased after static magnetic field exposure. The linearity of magnetosome chain was also affected by static magnetic field. Moreover, the applied intense magnetic field up-regulated mamA, mms13, magA expression when cultures were inoculated with magnetic cells, and mms13 expression in cultures inoculated with non-magnetic cells. The results implied that the interaction of the magnetic field created by magnetosomes in AMB-1 was affected by the imposed magnetic field. The applied static magnetic field could affect the formation of magnetic crystals and the arrangement of the neighboring magnetosome.

  9. Effect of oxidative stress on the growth of magnetic particles in Magnetospirillum magneticum.

    Science.gov (United States)

    Popa, Radu; Fang, Wen; Nealson, Kenneth H; Souza-Egipsy, Virginia; Berquó, Thelma S; Benerjee, Subir K; Penn, Lee R

    2009-03-01

    Individual magnetosome-containing magnetic mineral particles (MMP) from magnetotactic bacteria grow rapidly such that only a small fraction (5%) of all magnetosomes contain dwarf (Studies of the developmental stages in the growth of MMP are difficult due to the absence of techniques to separate dwarf from mature particles and because the former are sensitive to extraction procedures. Here, O2 stress was used to inhibit MMP expression in Magnetospirillum magneticum strain AMB-1. In addition, defined growth conditions not requiring chemical monitoring or manipulation of the gas composition during growth resulted in the production of cells containing high numbers of dwarf MMP. Cells exposed to different incubation treatments and cells with dwarf MMP were compared to cells with normal MMP with respect to growth, respiration, iron content, and relative magnetite load (RML). The cells were examined by electron microscopy, low temperature magnetometry, X-ray diffraction (XRD), and Mössbauer spectroscopy. In the 0-110 microM O2(aq) range, growth was positively correlated with [O2] and negatively correlated with RML. Most MMP formed during exponential growth of the cells. At 50-100 microM O2(aq) with stirring (150 rpm) and 30% O2 loss during incubation, MMP expression was strongly inhibited whereas MMP nucleation was not. Cells highly enriched (~95%) in dwarf MMP were obtained at the end of the exponential phase in stirred (150 rpm) cultures containing 45 microM O2(aq). Only one dwarf MMP formed in each MMP vesicle and the chain arrangement was largely preserved. O2-stress-induced dwarf MMP consisted of non-euhedral spheroids (~25 nm) that were similar in shape and size to immature MMP from normal cells. They consisted solely of magnetite, with a single domain signature, no superparamagnetic behavior, and magnetic signatures, Fe(II)/Fe(III) ratios, and XRD patterns very similar to those of mature MMP. These results show that O2 stress in liquid cultures amended with an

  10. Formation of Core-Shell Nanoparticles Composed of Magnetite and Samarium Oxide in Magnetospirillum magneticum Strain RSS-1

    Science.gov (United States)

    Shimoshige, Hirokazu; Nakajima, Yoshikata; Kobayashi, Hideki; Yanagisawa, Keiichi; Nagaoka, Yutaka; Shimamura, Shigeru; Mizuki, Toru; Inoue, Akira; Maekawa, Toru

    2017-01-01

    Magnetotactic bacteria (MTB) synthesize magnetosomes composed of membrane-enveloped magnetite (Fe3O4) or greigite (Fe3S4) particles in the cells. Recently, several studies have shown some possibilities of controlling the biomineralization process and altering the magnetic properties of magnetosomes by adding some transition metals to the culture media under various environmental conditions. Here, we successfully grow Magnetospirillum magneticum strain RSS-1, which are isolated from a freshwater environment, and find that synthesis of magnetosomes are encouraged in RSS-1 in the presence of samarium and that each core magnetic crystal composed of magnetite is covered with a thin layer of samarium oxide (Sm2O3). The present results show some possibilities of magnetic recovery of transition metals and synthesis of some novel structures composed of magnetic particles and transition metals utilizing MTB. PMID:28125741

  11. NCBI nr-aa BLAST: CBRC-RNOR-12-0032 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-RNOR-12-0032 ref|YP_421236.1| Signal transduction histidine kinase [Magnetospirillum magnetic...um AMB-1] dbj|BAE50677.1| Signal transduction histidine kinase [Magnetospirillum magneticum AMB-1] YP_421236.1 0.58 25% ...

  12. NCBI nr-aa BLAST: CBRC-XTRO-01-0470 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0470 ref|YP_419798.1| Ice nucleation protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE49239.1| Ice nucleation protein [Magnetospirillum magneticum AMB-1] YP_419798.1 1e-13 24% ...

  13. NCBI nr-aa BLAST: CBRC-TGUT-27-0001 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-TGUT-27-0001 ref|YP_420821.1| Microcystin-dependent protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE50262.1| Microcystin-dependent protein [Magnetospirillum magneticum AMB-1] YP_420821.1 7.2 34% ...

  14. NCBI nr-aa BLAST: CBRC-XTRO-01-2513 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-2513 ref|YP_419798.1| Ice nucleation protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE49239.1| Ice nucleation protein [Magnetospirillum magneticum AMB-1] YP_419798.1 2e-12 28% ...

  15. NCBI nr-aa BLAST: CBRC-XTRO-01-0188 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0188 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 6e-04 27% ...

  16. NCBI nr-aa BLAST: CBRC-XTRO-01-0267 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0267 ref|YP_419798.1| Ice nucleation protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE49239.1| Ice nucleation protein [Magnetospirillum magneticum AMB-1] YP_419798.1 8e-16 18% ...

  17. NCBI nr-aa BLAST: CBRC-XTRO-01-0132 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0132 ref|YP_419798.1| Ice nucleation protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE49239.1| Ice nucleation protein [Magnetospirillum magneticum AMB-1] YP_419798.1 1e-21 25% ...

  18. NCBI nr-aa BLAST: CBRC-XTRO-01-0090 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0090 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 0.043 34% ...

  19. NCBI nr-aa BLAST: CBRC-XTRO-01-0635 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-0635 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 5e-05 27% ...

  20. NCBI nr-aa BLAST: CBRC-XTRO-01-3405 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-3405 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 8e-04 30% ...

  1. NCBI nr-aa BLAST: CBRC-XTRO-01-2304 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-2304 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 0.017 34% ...

  2. NCBI nr-aa BLAST: CBRC-LAFR-01-1856 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-LAFR-01-1856 ref|YP_420189.1| Transcriptional regulator [Magnetospirillum magnetic...um AMB-1] dbj|BAE49630.1| Transcriptional regulator [Magnetospirillum magneticum AMB-1] YP_420189.1 0.25 35% ...

  3. NCBI nr-aa BLAST: CBRC-TNIG-22-0115 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-TNIG-22-0115 ref|YP_419377.1| Ammonia permease [Magnetospirillum magneticum AM...B-1] dbj|BAE48818.1| Ammonia permease [Magnetospirillum magneticum AMB-1] YP_419377.1 5e-04 30% ...

  4. NCBI nr-aa BLAST: CBRC-XTRO-01-3964 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-3964 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 0.002 26% ...

  5. NCBI nr-aa BLAST: CBRC-DDIS-01-0175 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-DDIS-01-0175 ref|YP_422348.1| FAD/FMN-containing dehydrogenase [Magnetospirillum magnetic...um AMB-1] dbj|BAE51789.1| FAD/FMN-containing dehydrogenase [Magnetospirillum magneticum AMB-1] YP_422348.1 1e-105 48% ...

  6. NCBI nr-aa BLAST: CBRC-DSIM-06-0019 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-DSIM-06-0019 ref|YP_421580.1| hypothetical protein amb2217 [Magnetospirillum magnetic...um AMB-1] dbj|BAE51021.1| hypothetical protein [Magnetospirillum magneticum AMB-1] YP_421580.1 0.11 32% ...

  7. NCBI nr-aa BLAST: CBRC-XTRO-01-3821 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-3821 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 4e-04 27% ...

  8. NCBI nr-aa BLAST: CBRC-XTRO-01-2508 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-XTRO-01-2508 ref|YP_422165.1| Predicted membrane metal-binding protein [Magnetospirillum magnetic...um AMB-1] dbj|BAE51606.1| Predicted membrane metal-binding protein [Magnetospirillum magneticum AMB-1] YP_422165.1 0.002 27% ...

  9. NCBI nr-aa BLAST: CBRC-DYAK-06-0066 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-DYAK-06-0066 ref|YP_421580.1| hypothetical protein amb2217 [Magnetospirillum magnetic...um AMB-1] dbj|BAE51021.1| hypothetical protein [Magnetospirillum magneticum AMB-1] YP_421580.1 0.077 27% ...

  10. NCBI nr-aa BLAST: CBRC-OGAR-01-1183 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available CBRC-OGAR-01-1183 ref|YP_420327.1| Periplasmic protein TonB [Magnetospirillum magnetic...um AMB-1] dbj|BAE49768.1| Periplasmic protein TonB [Magnetospirillum magneticum AMB-1] YP_420327.1 0.019 25% ...

  11. N2-dependent growth and nitrogenase activity in the metal-metabolizing bacteria, Geobacter and Magnetospirillum species

    Science.gov (United States)

    Bazylinski, D.A.; Dean, A.J.; Schuler, D.; Phillips, E.J.P.; Lovley, D.R.

    2000-01-01

    Cells of Geobacter metallireducens, Magnetospirillum strain AMB-1, Magnetospirillum magnetotacticum and Magnetospirillum gryphiswaldense showed N2-dependent growth, the first anaerobically with Fe(lll) as the electron acceptor, and the latter three species micro-aerobically in semi-solid oxygen gradient cultures. Cells of the Magnetospirillum species grown with N2 under microaerobic conditions were magnetotactic and therefore produced magnetosomes. Cells of Geobacter metallireducens reduced acetylene to ethylene (11.5 ?? 5.9nmol C2H4 produced min-1 mg-1 cell protein) while growing with Fe(lll) as the electron acceptor in anaerobic growth medium lacking a fixed nitrogen source. Cells of the Magnetospirillum species, grown in a semi-solid oxygen gradient medium, also reduced acetylene at comparable rates. Uncut chromosomal and fragments from endonuclease-digested chromosomal DNA from these species, as well as Geobacter sulphurreducens organisms, hybridized with a nifHDK probe from Rhodospirillum rubrum, indicating the presence of these nitrogenase structural genes in these organisms. The evidence presented here shows that members of the metal-metabolizing genera, Geobacter and Magnetospirillum, fix atmospheric dinitrogen.

  12. Investigating Cell-Material Interactions of Magnetospirillum magneticum as an Approach for Probing Submerged Surface Structural Integrity

    Science.gov (United States)

    2012-07-01

    by which the pair of coils is offset (see Figure 1). We then programmed an Arduino Uno microcontroller to rapidly alternate between the...two coils. A circuit with a transistor (TIP 102) and diode (1N4004) was built to protect the Arduino as the maximum current for the Arduino is about

  13. Effect of Magnetospirillum gryphiswaldense on serum iron levels in mice

    Directory of Open Access Journals (Sweden)

    Tahereh Setayesh

    2012-09-01

    Full Text Available Background and Objectives: The Magnetotactic bacteria Magnetospirillum gryphiswaldense (MSR-1 mineralizes the magnetite (Fe3 O4 crystals and organizes a highly ordered intracellular structure, called the magnetosome. Iron transport system supports the biogenesis of magnetite. Although iron is an essential trace element for many metabolic pathways of the body, increase or decrease in iron will cause many diseases. Mice were infected by MSR-1 to study survival of bacteria in mice when injected by different routes. The aim of this study was to investigate whether bacterial magnetite formation could take up Fe2+ ions from the blood an animal model.Materials and Methods: In this study, MSR-1 at a dose lower than LD50 in 200 μl volume of PBS buffer was injected as intravascular (i.v, peritoneal (i.p and subcutaneous (s.c in mice. Number of viable bacterial was determined in organs such as liver, spleen and lymph node by measuring colony-forming unit (CFU. Moreover, serum iron level was evaluated by using commercial kits.Results and Conclusion: According to CFU measurements, after 96 hours, mice can clear MSR-1 from their body with different routes of injection. We have also shown that MSR-1 bacteria can affect the blood iron level in mice. The serum iron level decreased from control level in the first 24 h after i.v injection (P < 0.05. Our research on optimizing the biological magnetic system is still continuing.

  14. Mass-dependent and -independent signature of Fe isotopes in magnetotactic bacteria.

    Science.gov (United States)

    Amor, Matthieu; Busigny, Vincent; Louvat, Pascale; Gélabert, Alexandre; Cartigny, Pierre; Durand-Dubief, Mickaël; Ona-Nguema, Georges; Alphandéry, Edouard; Chebbi, Imène; Guyot, François

    2016-05-06

    Magnetotactic bacteria perform biomineralization of intracellular magnetite (Fe3O4) nanoparticles. Although they may be among the earliest microorganisms capable of biomineralization on Earth, identifying their activity in ancient sedimentary rocks remains challenging because of the lack of a reliable biosignature. We determined Fe isotope fractionations by the magnetotactic bacterium Magnetospirillum magneticum AMB-1. The AMB-1 strain produced magnetite strongly depleted in heavy Fe isotopes, by 1.5 to 2.5 per mil relative to the initial growth medium. Moreover, we observed mass-independent isotope fractionations in (57)Fe during magnetite biomineralization but not in even Fe isotopes ((54)Fe, (56)Fe, and (58)Fe), highlighting a magnetic isotope effect. This Fe isotope anomaly provides a potential biosignature for the identification of magnetite produced by magnetotactic bacteria in the geological record.

  15. SZ effects in the Magneticum Pathfinder Simulation: Comparison with the Planck, SPT, and ACT results

    CERN Document Server

    Dolag, Klaus; Sunyaev, Rashid

    2015-01-01

    We calculate the one-point probability density distribution functions (PDF) and the power spectra of the thermal and kinetic Sunyaev-Zeldovich (tSZ and kSZ) effects and the mean Compton Y parameter using the Magneticum Pathfinder simulations, state-of-the-art cosmological hydrodynamical simulations of a large cosmological volume of (896 Mpc/h)^3. These simulations follow in detail the thermal and chemical evolution of the intracluster medium as well as the evolution of super-massive black holes and their associated feedback processes. We construct full-sky maps of tSZ and kSZ from the light-cones out to z=0.17, and one realization of 8.8x8.8 degree wide, deep light-cone out to z=5.2. The local universe at z=1.18x10^{-6} for \\Omega_m=0.272 and \\sigma_8=0.809. Nearly half (~ 5x10^{-7}) of the signal comes from halos below a virial mass of 10^{13}M_\\odot/h. Scaling this to the Planck 2015 parameters, we find =1.57x10^{-6}. The PDF and the power spectrum of kSZ from our simulation agree broadly with the previous ...

  16. SZ effects in the Magneticum Pathfinder simulation: comparison with the Planck, SPT, and ACT results

    Science.gov (United States)

    Dolag, K.; Komatsu, E.; Sunyaev, R.

    2016-12-01

    We calculate the one-point probability density distribution functions (PDF) and the power spectra of the thermal and kinetic Sunyaev-Zeldovich (tSZ and kSZ) effects and the mean Compton Y parameter using the Magneticum Pathfinder simulations, state-of-the-art cosmological hydrodynamical simulations of a large cosmological volume of (896 Mpc h-1)3. These simulations follow in detail the thermal and chemical evolution of the intracluster medium as well as the evolution of supermassive black holes and their associated feedback processes. We construct full-sky maps of tSZ and kSZ from the light-cones out to z = 0.17, and one realization of 8.8° × 8.8° deep light-cone out to z = 5.2. The local universe at z half (≈5 × 10-7) of the signal comes from haloes below a virial mass of 1013 M⊙ h-1. Scaling this to the Planck 2015 parameters, we find bar{Y}=1.57× {}10^{-6}.

  17. Biosynthesis of magnetic nanoparticles by human mesenchymal stem cells following transfection with the magnetotactic bacterial gene mms6.

    Science.gov (United States)

    Elfick, Alistair; Rischitor, Grigore; Mouras, Rabah; Azfer, Asim; Lungaro, Lisa; Uhlarz, Marc; Herrmannsdörfer, Thomas; Lucocq, John; Gamal, Wesam; Bagnaninchi, Pierre; Semple, Scott; Salter, Donald M

    2017-01-04

    The use of stem cells to support tissue repair is facilitated by loading of the therapeutic cells with magnetic nanoparticles (MNPs) enabling magnetic tracking and targeting. Current methods for magnetizing cells use artificial MNPs and have disadvantages of variable uptake, cellular cytotoxicity and loss of nanoparticles on cell division. Here we demonstrate a transgenic approach to magnetize human mesenchymal stem cells (MSCs). MSCs are genetically modified by transfection with the mms6 gene derived from Magnetospirillum magneticum AMB-1, a magnetotactic bacterium that synthesises single-magnetic domain crystals which are incorporated into magnetosomes. Following transfection of MSCs with the mms6 gene there is bio-assimilated synthesis of intracytoplasmic magnetic nanoparticles which can be imaged by MR and which have no deleterious effects on cell proliferation, migration or differentiation. The assimilation of magnetic nanoparticle synthesis into mammalian cells creates a real and compelling, cytocompatible, alternative to exogenous administration of MNPs.

  18. Biosynthesis of magnetic nanoparticles by human mesenchymal stem cells following transfection with the magnetotactic bacterial gene mms6

    Science.gov (United States)

    Elfick, Alistair; Rischitor, Grigore; Mouras, Rabah; Azfer, Asim; Lungaro, Lisa; Uhlarz, Marc; Herrmannsdörfer, Thomas; Lucocq, John; Gamal, Wesam; Bagnaninchi, Pierre; Semple, Scott; Salter, Donald M

    2017-01-01

    The use of stem cells to support tissue repair is facilitated by loading of the therapeutic cells with magnetic nanoparticles (MNPs) enabling magnetic tracking and targeting. Current methods for magnetizing cells use artificial MNPs and have disadvantages of variable uptake, cellular cytotoxicity and loss of nanoparticles on cell division. Here we demonstrate a transgenic approach to magnetize human mesenchymal stem cells (MSCs). MSCs are genetically modified by transfection with the mms6 gene derived from Magnetospirillum magneticum AMB-1, a magnetotactic bacterium that synthesises single-magnetic domain crystals which are incorporated into magnetosomes. Following transfection of MSCs with the mms6 gene there is bio-assimilated synthesis of intracytoplasmic magnetic nanoparticles which can be imaged by MR and which have no deleterious effects on cell proliferation, migration or differentiation. The assimilation of magnetic nanoparticle synthesis into mammalian cells creates a real and compelling, cytocompatible, alternative to exogenous administration of MNPs. PMID:28051139

  19. Magnetite biomineralization in Magnetospirillum gryphiswaldense: time-resolved magnetic and structural studies.

    Science.gov (United States)

    Fdez-Gubieda, M Luisa; Muela, Alicia; Alonso, Javier; García-Prieto, Ana; Olivi, Luca; Fernández-Pacheco, Rodrigo; Barandiarán, José Manuel

    2013-04-23

    Magnetotactic bacteria biosynthesize magnetite nanoparticles of high structural and chemical purity that allow them to orientate in the geomagnetic field. In this work we have followed the process of biomineralization of these magnetite nanoparticles. We have performed a time-resolved study on magnetotactic bacteria Magnetospirillum gryphiswaldense strain MSR-1. From the combination of magnetic and structural studies by means of Fe K-edge X-ray absorption near edge structure (XANES) and high-resolution transmission electron microscopy we have identified and quantified two phases of Fe (ferrihydrite and magnetite) involved in the biomineralization process, confirming the role of ferrihydrite as the source of Fe ions for magnetite biomineralization in M. gryphiswaldense. We have distinguished two steps in the biomineralization process: the first, in which Fe is accumulated in the form of ferrihydrite, and the second, in which the magnetite is rapidly biomineralized from ferrihydrite. Finally, the XANES analysis suggests that the origin of the ferrihydrite could be at bacterial ferritin cores, characterized by a poorly crystalline structure and high phosphorus content.

  20. Effect of Polyethylene Glycol on the Formation of Magnetic Nanoparticles Synthesized by Magnetospirillum magnetotacticum MS-1.

    Directory of Open Access Journals (Sweden)

    Hirokazu Shimoshige

    Full Text Available Magnetotactic bacteria (MTB synthesize intracellular magnetic nanocrystals called magnetosomes, which are composed of either magnetite (Fe3O4 or greigite (Fe3S4 and covered with lipid membranes. The production of magnetosomes is achieved by the biomineralization process with strict control over the formation of magnetosome membrane vesicles, uptake and transport of iron ions, and synthesis of mature crystals. These magnetosomes have high potential for both biotechnological and nanotechnological applications, but it is still extremely difficult to grow MTB and produce a large amount of magnetosomes under the conventional cultural conditions. Here, we investigate as a first attempt the effect of polyethylene glycol (PEG added to the culture medium on the increase in the yield of magnetosomes formed in Magnetospirillum magnetotacticum MS-1. We find that the yield of the formation of magnetosomes can be increased up to approximately 130 % by adding PEG200 to the culture medium. We also measure the magnetization of the magnetosomes and find that the magnetosomes possess soft ferromagnetic characteristics and the saturation mass magnetization is increased by 7 %.

  1. Magnetic nanoparticles from Magnetospirillum gryphiswaldense increase the efficacy of thermotherapy in a model of colon carcinoma.

    Directory of Open Access Journals (Sweden)

    Silvia Mannucci

    Full Text Available Magnetic nanoparticles (MNPs are capable of generate heating power under the influence of alternating magnetic fields (AMF; this behaviour recently opened new scenarios for advanced biomedical applications, mainly as new promising tumor therapies. In this paper we have tested magnetic nanoparticles called magnetosomes (MNs: a class of MNPs naturally produced by magnetotactic bacteria. We extracted MNs from Magnetospirillum gryphiswaldense strain MSR-1 and tested the interaction with cellular elements and anti-neoplastic activity both in vitro and in vivo, with the aim of developing new therapeutic approaches for neoplastic diseases. In vitro experiments performed on Human Colon Carcinoma HT-29 cell cultures demonstrated a strong uptake of MNs with no evident signs of cytotoxicity and revealed three phases in the interaction: adherence, transport and accumulation in Golgi vesicles. In vivo studies were performed on subcutaneous tumors in mice; in this model MNs are administered by direct injection in the tumor volume, then a protocol consisting of three exposures to an AMF rated at 187 kHz and 23kA/m is carried out on alternate days, over a week. Tumors were monitored by Magnetic Resonance Imaging (MRI to obtain information about MNs distribution and possible tissue modifications induced by hyperthermia. Histological analysis showed fibrous and necrotic areas close to MNs injection sites in mice subjected to a complete thermotherapy protocol. These results, although concerning a specific tumor model, could be useful to further investigate the feasibility and efficacy of protocols based on MFH. Magnetic nanoparticles naturally produced and extracted from bacteria seem to be promising candidates for theranostic applications in cancer therapy.

  2. Submerged culture of Magne-tospirillum gryphiswaldense under N2-fixing condition and regulation of activity of nitrogen fixation

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A submerged culture technique for Magnetospirillum gryphiswaldense under the nitrogen-fixing condition (microaerobic and N-limited) was set up. In N-limited medium with Na-lactate as a sole carbon source, the optical density (A600 nm) and activity of nitrogen fixation of cells were 1.3 and 217 nmol of ethylene produced per hour per A600nm respectively within 21 h by three times of feeds. The pH and temperature were controlled at 7.2 and 30℃ respectively, and the oxygen concentration was controlled by sparging with N2 containing 0.4%-0.8% of O2. The activity of nitrogen fixation of cells was obviously inhibited by oxygen and ammonium. It indicated that the posttranslational regulation of nitrogenase existed in M. gryphiswaldense.

  3. Development of a novel method for screening of estrogenic compounds using nano-sized bacterial magnetic particles displaying estrogen receptor

    Energy Technology Data Exchange (ETDEWEB)

    Yoshino, Tomoko [Department of Biotechnology, Tokyo University of Agriculture and Technology, 2 24 16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Kato, Fukuichi [Department of Biotechnology, Tokyo University of Agriculture and Technology, 2 24 16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Takeyama, Haruko [Department of Biotechnology, Tokyo University of Agriculture and Technology, 2 24 16 Naka-cho, Koganei, Tokyo 184-8588 (Japan); Nakai, Makoto [Chemicals Assessment Center, Chemicals Evaluation and Research Institute, 1600 Shimo-Takano, Sugito-machi, Kitakatsushika-gun, Saitama 345-0043 (Japan); Yakabe, Yoshikuni [Chemicals Assessment Center, Chemicals Evaluation and Research Institute, 1600 Shimo-Takano, Sugito-machi, Kitakatsushika-gun, Saitama 345-0043 (Japan); Matsunaga, Tadashi [Department of Biotechnology, Tokyo University of Agriculture and Technology, 2 24 16 Naka-cho, Koganei, Tokyo 184-8588 (Japan)]. E-mail: tmatsuna@cc.tuat.ac.jp

    2005-03-14

    In this study, nano-sized bacterial magnetic particles (BMPs) displaying human estrogen receptor ligand binding domain (ERLBD) on the surface was successfully produced by the magnetic bacterium, Magnetospirillum magneticum AMB-1. Furthermore, a non-isotopic binding assay for estrogenic compounds using the BMPs displaying ERLBD was developed. A BMP membrane-specific protein, Mms16, was used as an anchor molecule to localize ERLBD on the surface of BMPs. ERLBD-BMP complexes were simply extracted by magnetic separation from ruptured AMB-1 transformants and used for the assay based on the competitive binding of alkaline phosphatase conjugated 17{beta}-estradiol (ALP-E2) as a tracer. Dissociation constant of the receptor was 2.3 nM. Inhibition curves were evaluated by the decrease in luminescence intensity resulting from the enzymatic reaction of alkaline phosphatase. The overall simplicity of this receptor binding assay results in a method that can be easily adapted to a high throughput format. Moreover, this method can be integrated into a fully-automated ligand screening system using magnetic separation.

  4. Self-recognition mechanism of MamA, a magnetosome-associated TPR-containing protein, promotes complex assembly.

    Science.gov (United States)

    Zeytuni, Natalie; Ozyamak, Ertan; Ben-Harush, Kfir; Davidov, Geula; Levin, Maxim; Gat, Yair; Moyal, Tal; Brik, Ashraf; Komeili, Arash; Zarivach, Raz

    2011-08-16

    The magnetosome, a biomineralizing organelle within magnetotactic bacteria, allows their navigation along geomagnetic fields. Magnetosomes are membrane-bound compartments containing magnetic nanoparticles and organized into a chain within the cell, the assembly and biomineralization of magnetosomes are controlled by magnetosome-associated proteins. Here, we describe the crystal structures of the magnetosome-associated protein, MamA, from Magnetospirillum magneticum AMB-1 and Magnetospirillum gryphiswaldense MSR-1. MamA folds as a sequential tetra-trico-peptide repeat (TPR) protein with a unique hook-like shape. Analysis of the MamA structures indicates two distinct domains that can undergo conformational changes. Furthermore, structural analysis of seven crystal forms verified that the core of MamA is not affected by crystallization conditions and identified three protein-protein interaction sites, namely a concave site, a convex site, and a putative TPR repeat. Additionally, relying on transmission electron microscopy and size exclusion chromatography, we show that highly stable complexes form upon MamA homooligomerization. Disruption of the MamA putative TPR motif or N-terminal domain led to protein mislocalization in vivo and prevented MamA oligomerization in vitro. We, therefore, propose that MamA self-assembles through its putative TPR motif and its concave site to create a large homooligomeric scaffold which can interact with other magnetosome-associated proteins via the MamA convex site. We discuss the structural basis for TPR homooligomerization that allows the proper function of a prokaryotic organelle.

  5. Controlled cobalt doping in the spinel structure of magnetosome magnetite: new evidences from element- and site-specific X-ray magnetic circular dichroism analyses

    Science.gov (United States)

    Menguy, Nicolas; Arrio, Marie-Anne; Sainctavit, Philippe; Juhin, Amélie; Wang, Yinzhao; Chen, Haitao; Bunau, Oana; Otero, Edwige; Ohresser, Philippe; Pan, Yongxin

    2016-01-01

    The biomineralization of magnetite nanocrystals (called magnetosomes) by magnetotactic bacteria (MTB) has attracted intense interest in biology, geology and materials science due to the precise morphology of the particles, the chain-like assembly and their unique magnetic properties. Great efforts have been recently made in producing transition metal-doped magnetosomes with modified magnetic properties for a range of applications. Despite some successful outcomes, the coordination chemistry and magnetism of such metal-doped magnetosomes still remain largely unknown. Here, we present new evidences from X-ray magnetic circular dichroism (XMCD) for element- and site-specific magnetic analyses that cobalt is incorporated in the spinel structure of the magnetosomes within Magnetospirillum magneticum AMB-1 through the replacement of Fe2+ ions by Co2+ ions in octahedral (Oh) sites of magnetite. Both XMCD at Fe and Co L2,3 edges, and energy-dispersive X-ray spectroscopy on transmission electron microscopy analyses reveal a heterogeneous distribution of cobalt occurring either in different particles or inside individual particles. Compared with non-doped one, cobalt-doped magnetosome sample has lower Verwey transition temperature and larger magnetic coercivity, related to the amount of doped cobalt. This study also demonstrates that the addition of trace cobalt in the growth medium can significantly improve both the cell growth and the magnetosome formation within M. magneticum AMB-1. Together with the cobalt occupancy within the spinel structure of magnetosomes, this study indicates that MTB may provide a promising biomimetic system for producing chains of metal-doped single-domain magnetite with an appropriate tuning of the magnetic properties for technological and biomedical applications. PMID:27512138

  6. Controlled cobalt doping in the spinel structure of magnetosome magnetite: new evidences from element- and site-specific X-ray magnetic circular dichroism analyses.

    Science.gov (United States)

    Li, Jinhua; Menguy, Nicolas; Arrio, Marie-Anne; Sainctavit, Philippe; Juhin, Amélie; Wang, Yinzhao; Chen, Haitao; Bunau, Oana; Otero, Edwige; Ohresser, Philippe; Pan, Yongxin

    2016-08-01

    The biomineralization of magnetite nanocrystals (called magnetosomes) by magnetotactic bacteria (MTB) has attracted intense interest in biology, geology and materials science due to the precise morphology of the particles, the chain-like assembly and their unique magnetic properties. Great efforts have been recently made in producing transition metal-doped magnetosomes with modified magnetic properties for a range of applications. Despite some successful outcomes, the coordination chemistry and magnetism of such metal-doped magnetosomes still remain largely unknown. Here, we present new evidences from X-ray magnetic circular dichroism (XMCD) for element- and site-specific magnetic analyses that cobalt is incorporated in the spinel structure of the magnetosomes within Magnetospirillum magneticum AMB-1 through the replacement of Fe(2+) ions by Co(2+) ions in octahedral (Oh) sites of magnetite. Both XMCD at Fe and Co L2,3 edges, and energy-dispersive X-ray spectroscopy on transmission electron microscopy analyses reveal a heterogeneous distribution of cobalt occurring either in different particles or inside individual particles. Compared with non-doped one, cobalt-doped magnetosome sample has lower Verwey transition temperature and larger magnetic coercivity, related to the amount of doped cobalt. This study also demonstrates that the addition of trace cobalt in the growth medium can significantly improve both the cell growth and the magnetosome formation within M. magneticum AMB-1. Together with the cobalt occupancy within the spinel structure of magnetosomes, this study indicates that MTB may provide a promising biomimetic system for producing chains of metal-doped single-domain magnetite with an appropriate tuning of the magnetic properties for technological and biomedical applications. © 2016 The Author(s).

  7. Magnetotaxis as a means for nanofabrication of bioelectronics

    Science.gov (United States)

    Macwan, Isaac

    Self-assembly plays an important role in the formation of different nanostructures either organic or inorganic. Controlled assembly of molecules into higher ordered hierarchical structures on the other hand require a thorough insight into the interactive forces that lie behind such an assembly. The interface between organic and inorganic materials is thus of primary significance when it comes to the tasks of selective deposition and assembly of inorganic molecules through organic agents. One of the bacterial species that belong to the class alpha-proteobacteria called Magnetospirillum magneticum (classified as AMB-1) is investigated in this study and it is found that this species is able to fulfill the requirements that are imposed by the complexity of the selective deposition and controlled assembly tasks. AMB-1 contain single-domain crystals of magnetite (Fe3O4) called magnetosomes that sense the external magnetic field that is further utilized for cellular displacement (magnetotaxis) through lash-like cellular appendages called flagella. The two flagella located at the proximal and distal ends of the cell consists of a protein monomer flagellin. Individual flagellin in turn that are located on the periphery of each of the flagellum's central channel consists of four sub-domains, two inner domains (D0, D1) made up of alpha-helices and two outer domains (D2, D3) made up of beta sheets. However, it is the domain D3 that is exposed to the surrounding micro-environment, thereby interacting with the components to be selectively deposited, in this case, carbon nanotubes (CNT). Based on the electromagnetic and molecular dynamics simulations and the real-time experimental analysis involving optical microscopy utilizing 50 micron diameter conductor (44AWG) magnetic coils as directional magnetic field generation centers to visualize the motion of free as well as loaded AMB-1 as well as electron microscopy (TEM & SEM) to analyze the interactive forces between CNT and AMB-1

  8. Effects of dissolved oxygen concentration and iron addition on immediate-early gene expression of Magnetospirillum gryphiswaldense MSR-1.

    Science.gov (United States)

    Zhuang, Shiwen; Anyaogu, Diana Chinyere; Kasama, Takeshi; Workman, Mhairi; Mortensen, Uffe Hasbro; Hobley, Timothy John

    2017-06-15

    We report the effects of dissolved oxygen (DO) concentration and iron addition on gene expression of Magnetospirillum gryphiswaldense MSR-1 cells during fermentations, focusing on 0.25-24 h after iron addition. The DO was strictly controlled at 0.5% or 5% O2, and compared with aerobic condition. Uptake of iron (and formation of magnetosomes) was only observed in the 0.5% O2 condition where there was little difference in cell growth and carbon consumption compared to the 5% O2 condition. Quantitative reverse transcription PCR analysis showed a rapid (within 0.25 h) genetic response of MSR-1 cells after iron addition for all the genes studied, except for MgFnr (oxygen sensor gene) and fur (ferric uptake regulator family gene), and which in some cases was oxygen dependent. In particular, expression of sodB1 (superoxide dismutase gene) and feoB1 (ferrous transport protein B1 gene) was markedly reduced in cultures at 0.5% O2 compared to those at higher oxygen tensions. Moreover, expression of katG (catalase-peroxidase gene) and feoB2 (ferrous transport protein B2 gene) was reduced markedly by iron addition, regardless of oxygen conditions. These data provide a greater understanding of molecular response of MSR-1 cells to environmental conditions associated with oxygen and iron metabolisms, especially relevant to immediate-early stage of fermentation. © FEMS 2017. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  9. Characterization of a spontaneous nonmagnetic mutant of Magnetospirillum gryphiswaldense reveals a large deletion comprising a putative magnetosome island.

    Science.gov (United States)

    Schübbe, Sabrina; Kube, Michael; Scheffel, André; Wawer, Cathrin; Heyen, Udo; Meyerdierks, Anke; Madkour, Mohamed H; Mayer, Frank; Reinhardt, Richard; Schüler, Dirk

    2003-10-01

    Frequent spontaneous loss of the magnetic phenotype was observed in stationary-phase cultures of the magnetotactic bacterium Magnetospirillum gryphiswaldense MSR-1. A nonmagnetic mutant, designated strain MSR-1B, was isolated and characterized. The mutant lacked any structures resembling magnetosome crystals as well as internal membrane vesicles. The growth of strain MSR-1B was impaired under all growth conditions tested, and the uptake and accumulation of iron were drastically reduced under iron-replete conditions. A large chromosomal deletion of approximately 80 kb was identified in strain MSR-1B, which comprised both the entire mamAB and mamDC clusters as well as further putative operons encoding a number of magnetosome-associated proteins. A bacterial artificial chromosome clone partially covering the deleted region was isolated from the genomic library of wild-type M. gryphiswaldense. Sequence analysis of this fragment revealed that all previously identified mam genes were closely linked with genes encoding other magnetosome-associated proteins within less than 35 kb. In addition, this region was remarkably rich in insertion elements and harbored a considerable number of unknown gene families which appeared to be specific for magnetotactic bacteria. Overall, these findings suggest the existence of a putative large magnetosome island in M. gryphiswaldense and other magnetotactic bacteria.

  10. Single-step production of a recyclable nanobiocatalyst for organophosphate pesticides biodegradation using functionalized bacterial magnetosomes.

    Directory of Open Access Journals (Sweden)

    Nicolas Ginet

    Full Text Available Enzymes are versatile catalysts in laboratories and on an industrial scale; improving their immobilization would be beneficial to broadening their applicability and ensuring their (reuse. Lipid-coated nano-magnets produced by magnetotactic bacteria are suitable for a universally applicable single-step method of enzyme immobilization. By genetically functionalizing the membrane surrounding these magnetite particles with a phosphohydrolase, we engineered an easy-to-purify, robust and recyclable biocatalyst to degrade ethyl-paraoxon, a commonly used pesticide. For this, we genetically fused the opd gene from Flavobacterium sp. ATCC 27551 encoding a paraoxonase to mamC, an abundant protein of the magnetosome membrane in Magnetospirillum magneticum AMB-1. The MamC protein acts as an anchor for the paraoxonase to the magnetosome surface, thus producing magnetic nanoparticles displaying phosphohydrolase activity. Magnetosomes functionalized with Opd were easily recovered from genetically modified AMB-1 cells: after cellular disruption with a French press, the magnetic nanoparticles are purified using a commercially available magnetic separation system. The catalytic properties of the immobilized Opd were measured on ethyl-paraoxon hydrolysis: they are comparable with the purified enzyme, with K(m (and k(cat values of 58 µM (and 178 s(-1 and 43 µM (and 314 s(-1 for the immobilized and purified enzyme respectively. The Opd, a metalloenzyme requiring a zinc cofactor, is thus properly matured in AMB-1. The recycling of the functionalized magnetosomes was investigated and their catalytic activity proved to be stable over repeated use for pesticide degradation. In this study, we demonstrate the easy production of functionalized magnetic nanoparticles with suitably genetically modified magnetotactic bacteria that are efficient as a reusable nanobiocatalyst for pesticides bioremediation in contaminated effluents.

  11. Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosomes deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1

    Institute of Scientific and Technical Information of China (English)

    LI; Feng; LI; Ying; JIANG; Wei; WANG; Zhenfang; LI; Jilun

    2005-01-01

    A magnetosome deleted mutant NM4 of Magnetospirillum gryphiswaldense MSR-1 was generated by mini-Tn5 transposon mutagenesis, and a 5045-bp fragment flanking mini-Tn5 in NM4 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved six putative open reading frames (ORFs); the mini-Tn5 was inserted into ORF4. Functional complementary test indicated that the 5045-bp fragment was required for biosynthesis of magnetosomes in M. gryphiswaldense MSR-1. The protein encoded by ORF4 had 25% of identity with the chemotaxis protein CheYIII of Caulobacter crescentus CB15, and the protein encoded by ORF4 contained a conserved signal receiver domain that can receive the signal from the sensor partner of the bacterial two-component systems. It was suggested that the protein encoded by ORF4 may take part in the signal transduction relating to biosynthesis of magnetosomes.

  12. Isolation and characterization of Magnetospirillum sp. strain 15-1 as a representative anaerobic toluene-degrader from a constructed wetland model.

    Science.gov (United States)

    Meyer-Cifuentes, Ingrid; Martinez-Lavanchy, Paula M; Marin-Cevada, Vianey; Böhnke, Stefanie; Harms, Hauke; Müller, Jochen A; Heipieper, Hermann J

    2017-01-01

    Previously, Planted Fixed-Bed Reactors (PFRs) have been used to investigate microbial toluene removal in the rhizosphere of constructed wetlands. Aerobic toluene degradation was predominant in these model systems although bulk redox conditions were hypoxic to anoxic. However, culture-independent approaches indicated also that microbes capable of anaerobic toluene degradation were abundant. Therefore, we aimed at isolating anaerobic-toluene degraders from one of these PFRs. From the obtained colonies which consisted of spirilli-shaped bacteria, a strain designated 15-1 was selected for further investigations. Analysis of its 16S rRNA gene revealed greatest similarity (99%) with toluene-degrading Magnetospirillum sp. TS-6. Isolate 15-1 grew with up to 0.5 mM of toluene under nitrate-reducing conditions. Cells reacted to higher concentrations of toluene by an increase in the degree of saturation of their membrane fatty acids. Strain 15-1 contained key genes for the anaerobic degradation of toluene via benzylsuccinate and subsequently the benzoyl-CoA pathway, namely bssA, encoding for the alpha subunit of benzylsuccinate synthase, bcrC for subunit C of benzoyl-CoA reductase and bamA for 6-oxocyclohex-1-ene-1-carbonyl-CoA hydrolase. Finally, most members of a clone library of bssA generated from the PFR had highest similarity to bssA from strain 15-1. Our study provides insights about the physiological capacities of a strain of Magnetospirillum isolated from a planted system where active rhizoremediation of toluene is taking place.

  13. Isolation and characterization of Magnetospirillum sp. strain 15-1 as a representative anaerobic toluene-degrader from a constructed wetland model

    Science.gov (United States)

    Meyer-Cifuentes, Ingrid; Martinez-Lavanchy, Paula M.; Marin-Cevada, Vianey; Böhnke, Stefanie; Harms, Hauke; Müller, Jochen A.

    2017-01-01

    Previously, Planted Fixed-Bed Reactors (PFRs) have been used to investigate microbial toluene removal in the rhizosphere of constructed wetlands. Aerobic toluene degradation was predominant in these model systems although bulk redox conditions were hypoxic to anoxic. However, culture-independent approaches indicated also that microbes capable of anaerobic toluene degradation were abundant. Therefore, we aimed at isolating anaerobic-toluene degraders from one of these PFRs. From the obtained colonies which consisted of spirilli-shaped bacteria, a strain designated 15–1 was selected for further investigations. Analysis of its 16S rRNA gene revealed greatest similarity (99%) with toluene-degrading Magnetospirillum sp. TS-6. Isolate 15–1 grew with up to 0.5 mM of toluene under nitrate-reducing conditions. Cells reacted to higher concentrations of toluene by an increase in the degree of saturation of their membrane fatty acids. Strain 15–1 contained key genes for the anaerobic degradation of toluene via benzylsuccinate and subsequently the benzoyl-CoA pathway, namely bssA, encoding for the alpha subunit of benzylsuccinate synthase, bcrC for subunit C of benzoyl-CoA reductase and bamA for 6-oxocyclohex-1-ene-1-carbonyl-CoA hydrolase. Finally, most members of a clone library of bssA generated from the PFR had highest similarity to bssA from strain 15–1. Our study provides insights about the physiological capacities of a strain of Magnetospirillum isolated from a planted system where active rhizoremediation of toluene is taking place. PMID:28369150

  14. Functional expression of an scFv on bacterial magnetic particles by in vitro docking

    Energy Technology Data Exchange (ETDEWEB)

    Sugamata, Yasuhiro; Tanaka, Tsuyoshi; Matsunaga, Tadashi; Yoshino, Tomoko, E-mail: y-tomoko@cc.tuat.ac.jp

    2014-02-28

    Highlights: • We present a novel expression system called “in vitro docking” on bacterial magnetic particles. • An scFv–Fc was functionally expressed on bacterial magnetic particles of magnetotactic bacteria. • Our novel expression system on BacMPs will be effective for disulfide-bonded proteins. - Abstract: A Gram-negative, magnetotactic bacterium, Magnetospirillum magneticum AMB-1 produces nano-sized magnetic particles (BacMPs) in the cytoplasm. Although various applications of genetically engineered BacMPs have been demonstrated, such as immunoassay, ligand–receptor interaction or cell separation, by expressing a target protein on BacMPs, it has been difficult to express disulfide-bonded proteins on BacMPs due to lack of disulfide-bond formation in the cytoplasm. Here, we propose a novel dual expression system, called in vitro docking, of a disulfide-bonded protein on BacMPs by directing an immunoglobulin Fc-fused target protein to the periplasm and its docking protein ZZ on BacMPs. By in vitro docking, an scFv–Fc fusion protein was functionally expressed on BacMPs in the dimeric or trimeric form. Our novel disulfide-bonded protein expression system on BacMPs will be useful for efficient screening of potential ligands or drugs, analyzing ligand–receptor interactions or as a magnetic carrier for affinity purification.

  15. Integrated Self-Assembly of the Mms6 Magnetosome Protein to Form an Iron-Responsive Structure

    Directory of Open Access Journals (Sweden)

    Marit Nilsen-Hamilton

    2013-07-01

    Full Text Available A common feature of biomineralization proteins is their self-assembly to produce a surface consistent in size with the inorganic crystals that they produce. Mms6, a small protein of 60 amino acids from Magnetospirillum magneticum strain AMB-1 that promotes the in vitro growth of superparamagnetic magnetite nanocrystals, assembles in aqueous solution to form spherical micelles that could be visualized by TEM and AFM. The results reported here are consistent with the view that the N and C-terminal domains interact with each other within one polypeptide chain and across protein units in the assembly. From studies to determine the amino acid residues important for self-assembly, we identified the unique GL repeat in the N-terminal domain with additional contributions from amino acids in other positions, throughout the molecule. Analysis by CD spectroscopy identified a structural change in the iron-binding C-terminal domain in the presence of Fe3+. A change in the intrinsic fluorescence of tryptophan in the N-terminal domain showed that this structural change is transmitted through the protein. Thus, self-assembly of Mms6 involves an interlaced structure of intra- and inter-molecular interactions that results in a coordinated structural change in the protein assembly with iron binding.

  16. MamO Is a Repurposed Serine Protease that Promotes Magnetite Biomineralization through Direct Transition Metal Binding in Magnetotactic Bacteria

    Science.gov (United States)

    Hershey, David M.; Ren, Xuefeng; Melnyk, Ryan A.; Browne, Patrick J.; Ozyamak, Ertan; Jones, Stephanie R.; Chang, Michelle C. Y.; Hurley, James H.; Komeili, Arash

    2016-01-01

    Many living organisms transform inorganic atoms into highly ordered crystalline materials. An elegant example of such biomineralization processes is the production of nano-scale magnetic crystals in magnetotactic bacteria. Previous studies implicated the involvement of two putative serine proteases, MamE and MamO, during the early stages of magnetite formation in Magnetospirillum magneticum AMB-1. Here, using genetic analysis and X-ray crystallography, we show that MamO has a degenerate active site, rendering it incapable of protease activity. Instead, MamO promotes magnetosome formation through two genetically distinct, noncatalytic activities: activation of MamE-dependent proteolysis of biomineralization factors and direct binding to transition metal ions. By solving the structure of the protease domain bound to a metal ion, we identify a surface-exposed di-histidine motif in MamO that contributes to metal binding and show that it is required to initiate biomineralization in vivo. Finally, we find that pseudoproteases are widespread in magnetotactic bacteria and that they have evolved independently in three separate taxa. Our results highlight the versatility of protein scaffolds in accommodating new biochemical activities and provide unprecedented insight into the earliest stages of biomineralization. PMID:26981620

  17. Energy losses in mechanically modified bacterial magnetosomes

    Science.gov (United States)

    Molcan, Matus; Gojzewski, Hubert; Skumiel, Andrzej; Dutz, Silvio; Kovac, Jozef; Kubovcikova, Martina; Kopcansky, Peter; Vekas, Ladislau; Timko, Milan

    2016-09-01

    Magnetosomes are isolated from the Magnetospirillum magneticum strain AMB-1 bacteria. Two samples are compared: magnetosomes normally prepared of a ‘standard’ length and magnetosomes of a short length. Chains of magnetosomes are shortened by mechanical modification (cleavage) by means of sonication treatment. They represent a new geometry of magnetosomes that have not been investigated before. The effect of the sonication is analysed using transmission and electron microscopy, atomic force microscopy, and dynamic light scattering. Scanning imaging reveals three types of shortening effect in a sample of shortened magnetosomes, namely, membrane collapse, membrane destruction, and magnetosome cleavage. Dynamic light scattering shows a reduction of hydrodynamic diameter in a sample of shortened magnetosomes. The magnetic properties of magnetosomes are analysed and compared in DC and AC magnetic fields based on the evaluation of quasi-static hysteresis loops (energy losses) and calorimetric hyperthermia measurements (specific absorption rate), respectively. A sample of shortened magnetosomes behaves magnetically in a different manner, showing that both the energy loss and the specific absorption rate are reduced, and thereby indicates a variation in the heating process. The magnetic properties of magnetosomes, together with the new and stable geometry, are balanced, which opens the way for a better adaptation of the magnetic field parameters for particular applications.

  18. MamO Is a Repurposed Serine Protease that Promotes Magnetite Biomineralization through Direct Transition Metal Binding in Magnetotactic Bacteria.

    Directory of Open Access Journals (Sweden)

    David M Hershey

    2016-03-01

    Full Text Available Many living organisms transform inorganic atoms into highly ordered crystalline materials. An elegant example of such biomineralization processes is the production of nano-scale magnetic crystals in magnetotactic bacteria. Previous studies implicated the involvement of two putative serine proteases, MamE and MamO, during the early stages of magnetite formation in Magnetospirillum magneticum AMB-1. Here, using genetic analysis and X-ray crystallography, we show that MamO has a degenerate active site, rendering it incapable of protease activity. Instead, MamO promotes magnetosome formation through two genetically distinct, noncatalytic activities: activation of MamE-dependent proteolysis of biomineralization factors and direct binding to transition metal ions. By solving the structure of the protease domain bound to a metal ion, we identify a surface-exposed di-histidine motif in MamO that contributes to metal binding and show that it is required to initiate biomineralization in vivo. Finally, we find that pseudoproteases are widespread in magnetotactic bacteria and that they have evolved independently in three separate taxa. Our results highlight the versatility of protein scaffolds in accommodating new biochemical activities and provide unprecedented insight into the earliest stages of biomineralization.

  19. The cation diffusion facilitator proteins MamB and MamM of Magnetospirillum gryphiswaldense have distinct and complex functions, and are involved in magnetite biomineralization and magnetosome membrane assembly

    DEFF Research Database (Denmark)

    Uebe, René; Junge, Katja; Henn, Verena

    2011-01-01

    Magnetotactic bacteria form chains of intracellular membrane‐enclosed, nanometre‐sized magnetite crystals for navigation along the earth's magnetic field. The assembly of these prokaryotic organelles requires several specific polypeptides. Among the most abundant proteins associated...... with the magnetosome membrane of Magnetospirillum gryphiswaldense are MamB and MamM, which were implicated in magnetosomal iron transport because of their similarity to the cation diffusion facilitator family. Here we demonstrate that MamB and MamM are multifunctional proteins involved in several steps of magnetosome...... formation. Whereas both proteins were essential for magnetite biomineralization, only deletion of mamB resulted in loss of magnetosome membrane vesicles. MamB stability depended on the presence of MamM by formation of a heterodimer complex. In addition, MamB was found to interact with several other proteins...

  20. Bacterial host and reporter gene optimization for genetically encoded whole cell biosensors.

    Science.gov (United States)

    Brutesco, Catherine; Prévéral, Sandra; Escoffier, Camille; Descamps, Elodie C T; Prudent, Elsa; Cayron, Julien; Dumas, Louis; Ricquebourg, Manon; Adryanczyk-Perrier, Géraldine; de Groot, Arjan; Garcia, Daniel; Rodrigue, Agnès; Pignol, David; Ginet, Nicolas

    2017-01-01

    Whole-cell biosensors based on reporter genes allow detection of toxic metals in water with high selectivity and sensitivity under laboratory conditions; nevertheless, their transfer to a commercial inline water analyzer requires specific adaptation and optimization to field conditions as well as economical considerations. We focused here on both the influence of the bacterial host and the choice of the reporter gene by following the responses of global toxicity biosensors based on constitutive bacterial promoters as well as arsenite biosensors based on the arsenite-inducible Pars promoter. We observed important variations of the bioluminescence emission levels in five different Escherichia coli strains harboring two different lux-based biosensors, suggesting that the best host strain has to be empirically selected for each new biosensor under construction. We also investigated the bioluminescence reporter gene system transferred into Deinococcus deserti, an environmental, desiccation- and radiation-tolerant bacterium that would reduce the manufacturing costs of bacterial biosensors for commercial water analyzers and open the field of biodetection in radioactive environments. We thus successfully obtained a cell survival biosensor and a metal biosensor able to detect a concentration as low as 100 nM of arsenite in D. deserti. We demonstrated that the arsenite biosensor resisted desiccation and remained functional after 7 days stored in air-dried D. deserti cells. We also report here the use of a new near-infrared (NIR) fluorescent reporter candidate, a bacteriophytochrome from the magnetotactic bacterium Magnetospirillum magneticum AMB-1, which showed a NIR fluorescent signal that remained optimal despite increasing sample turbidity, while in similar conditions, a drastic loss of the lux-based biosensors signal was observed.

  1. A novel design strategy for nanoparticles on nanopatterns: interferometric lithographic patterning of Mms6 biotemplated magnetic nanoparticles.

    Science.gov (United States)

    Bird, S M; El-Zubir, O; Rawlings, A E; Leggett, G J; Staniland, S S

    2016-05-14

    Nanotechnology demands the synthesis of highly precise, functional materials, tailored for specific applications. One such example is bit patterned media. These high-density magnetic data-storage materials require specific and uniform magnetic nanoparticles (MNPs) to be patterned over large areas (cm(2) range) in exact nanoscale arrays. However, the realisation of such materials for nanotechnology applications depends upon reproducible fabrication methods that are both precise and environmentally-friendly, for cost-effective scale-up. A potentially ideal biological fabrication methodology is biomineralisation. This is the formation of inorganic minerals within organisms, and is known to be highly controlled down to the nanoscale whilst being carried out under ambient conditions. The magnetotactic bacterium Magnetospirillum magneticum AMB-1 uses a suite of dedicated biomineralisation proteins to control the formation of magnetite MNPs within their cell. One of these proteins, Mms6, has been shown to control formation of magnetite MNPs in vitro. We have previously used Mms6 on micro-contact printed (μCP) patterned self-assembled monolayer (SAM) surfaces to control the formation and location of MNPs in microscale arrays, offering a bioinspired and green-route to fabrication. However, μCP cannot produce patterns reliably with nanoscale dimensions, and most alternative nanofabrication techniques are slow and expensive. Interferometric lithography (IL) uses the interference of laser light to produce nanostructures over large areas via a simple process implemented under ambient conditions. Here we combine the bottom-up biomediated approach with a top down IL methodology to produce arrays of uniform magnetite MNPs (86 ± 21 nm) with a period of 357 nm. This shows a potentially revolutionary strategy for the production of magnetic arrays with nanoscale precision in a process with low environmental impact, which could be scaled readily to facilitate large-scale production

  2. Magnetospirillum gryphiswaldense MSR-1磁小体缺失突变株NM4 Tn5侧翼序列的克隆及功能分析

    Institute of Scientific and Technical Information of China (English)

    李峰; 李颖; 姜伟; 王珍芳; 李季伦

    2005-01-01

    利用mini-Tn5 lacZ2对格瑞菲斯瓦尔德磁螺菌(Magnetospirillum gryphiswaldense)MSR-1进行转座插入突变, 获得磁小体缺失突变株NM4.通过锚定PCR(anchored PCR)从NM4中克隆出Tn5插入位点的侧翼序列, 获得长5045 bp的DNA 片段, 其中含有6个ORFs, Tn5插入在ORF4中.功能互补实验证明该片段与磁小体的合成有关.对ORF4编码的蛋白进行同源比较和功能分析, 发现ORF4编码的蛋白与Caulobacter crescentus CB15的长为200 AA的趋化蛋白CheYIII的同源性为25% (30/116), 且ORF4编码的蛋白也具有与CheYIII相同的接收磷酸基团的REC结构域, 可进行信号传递, 因此推测ORF4编码的蛋白可能参与磁小体合成过程中的某种(低氧分压或铁离子浓度)信号的转导.

  3. Controlled cobalt doping in the spinel structure of magnetosome magnetite: New evidences from element- and site-specific XMCD analyses

    Science.gov (United States)

    Pan, Y.; LI, J.; Menguy, N.; Arrio, M. A.; Sainctavit, P.; Juhin, A.; Wang, Y.; Chen, H.; Bunau, O.; Otero, E.; Ohresser, P.

    2016-12-01

    Controlled cobalt doping in the spinel structure of magnetosome magnetite: New evidences from element- and site-specific XMCD analyses Jinhua Li1,2*, Nicolas Menguy2,3, Marie-Anne Arrio3, Philippe Sainctavit3,4, Amélie Juhin3, Yinzhao Wang1,2, Haitao Chen5, Oana Bunau3, Edwige Otero4, Philippe Ohresser4, Yongxin Pan1,21Key Laboratory of Earth and Planetary Physics, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China. 2France-China Biomineralization and Nano-structures Laboratory, Chinese Academy of Sciences, Beijing 100029, China. 3IMPMC, CNRS UMR 7590, Sorbonne Universités, MNHN, UPMC, IRD UMR 206, 75005 Paris, France. 4Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin, 91192 Gif-sur-Yvette Cedex, France. 5Institute of Deep-Sea Science and Engineering, Chinese Academy of Sciences, Sanya 572000, China *To whom correspondence may be addressed. Email: lijinhua@mail.iggcas.ac.cnThe biomineralization of magnetite nanocrystals (called magnetosomes) by magnetotactic bacteria (MTB) has attracted intense interest in biology, geology and materials science. Great efforts have been recently made in producing transition metal-doped magnetosomes with modified magnetic properties for a range of applications. However, the coordination chemistry and magnetism of such metal-doped magnetosomes still remains largely unknown. Here, we present new evidences from X-ray magnetic circular dichroism (XMCD) for element- and site-specific magnetic analyses that cobalt is incorporated in the spinel structure of the magnetosomes within Magnetospirillum magneticum AMB-1 through the replacement of Fe2+ ions by Co2+ ions in octahedral (Oh) sites of magnetite. Compared with non-doped one, cobalt-doped magnetosome sample has lower Verwey transition temperature and larger magnetic coercivity, related to the amount of doped cobalt. This study this study indicates a biologically controlled process on cobalt doping and magnetic alteration by MTB system

  4. Molecular Mechanism of Bacterial Magnetite Formation and Its Application

    Science.gov (United States)

    2002-04-01

    human immunoglobin G (1gG) [35]. Also, the feasibility of Mmsl6 as an anchor molecule was established by manifesting the estrogen receptor hormone...functional foreign proteins. Similarly, immunoglobulin (IgG) binding cell wall protein and proteinA , 1Ml Magntetospillium magneticum AMB-1Protei nA magB...bacterial magnetic particle using magA gene fusion. were introduced to BMP membranes, using a proteinA -mrag.4 hybrid gene [34]. Using antibody bound proteinA

  5. Chemiluminescence enzyme immunoassay using ProteinA-bacterial magnetite complex

    Science.gov (United States)

    Matsunaga, Tadashi; Sato, Rika; Kamiya, Shinji; Tanaka, Tsuyosi; Takeyama, Haruko

    1999-04-01

    Bacterial magnetic particles (BMPs) which have ProteinA expressed on their surface were constructed using magA which is a key gene in BMP biosynthesis in the magnetic bacterium Magnetospirillum sp. AMB-1. Homogenous chemiluminescence enzyme immunoassay using antibody bound ProteinA-BMP complexes was developed for detection of human IgG. A good correlation between the luminescence yield and the concentration of human IgG was obtained in the range of 1-10 3 ng/ml.

  6. Bioinspired synthesis of magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    David, Anand [Iowa State Univ., Ames, IA (United States)

    2009-01-01

    The synthesis of magnetic nanoparticles has long been an area of active research. Magnetic nanoparticles can be used in a wide variety of applications such as magnetic inks, magnetic memory devices, drug delivery, magnetic resonance imaging (MRI) contrast agents, and pathogen detection in foods. In applications such as MRI, particle uniformity is particularly crucial, as is the magnetic response of the particles. Uniform magnetic particles with good magnetic properties are therefore required. One particularly effective technique for synthesizing nanoparticles involves biomineralization, which is a naturally occurring process that can produce highly complex nanostructures. Also, the technique involves mild conditions (ambient temperature and close to neutral pH) that make this approach suitable for a wide variety of materials. The term 'bioinspired' is important because biomineralization research is inspired by the naturally occurring process, which occurs in certain microorganisms called 'magnetotactic bacteria'. Magnetotactic bacteria use biomineralization proteins to produce magnetite crystals having very good uniformity in size and morphology. The bacteria use these magnetic particles to navigate according to external magnetic fields. Because these bacteria synthesize high quality crystals, research has focused on imitating aspects of this biomineralization in vitro. In particular, a biomineralization iron-binding protein found in a certain species of magnetotactic bacteria, magnetospirillum magneticum, AMB-1, has been extracted and used for in vitro magnetite synthesis; Pluronic F127 gel was used to increase the viscosity of the reaction medium to better mimic the conditions in the bacteria. It was shown that the biomineralization protein mms6 was able to facilitate uniform magnetite synthesis. In addition, a similar biomineralization process using mms6 and a shorter version of this protein, C25, has been used to synthesize cobalt ferrite

  7. Photoemission electron microscopy and scanning electron microscopy of Magnetospirillum magnetotacticum's magnetosome chains.

    Science.gov (United States)

    Keutner, Christoph; von Bohlen, Alex; Berges, Ulf; Espeter, Philipp; Schneider, Claus M; Westphal, Carsten

    2014-10-01

    Magnetotactic bacteria are of great interdisciplinary interest, since a vast field of applications from magnetic recording media to medical nanorobots is conceivable. A key feature for a further understanding is the detailed knowledge about the magnetosome chain within the bacteria. We report on two preparation procedures suitable for UHV experiments in reflective geometry. Further, we present the results of scanning electron microscopy, as well as the first photoemission electron microscopy experiments, both accessing the magnetosomes within intact magnetotactic bacteria and compare these to scanning electron microscopy data from the literature. From the images, we can clearly identify individual magnetosomes within their chains.

  8. Biosynthesis and the conjugation of magnetite nanoparticles with luteinizing hormone releasing hormone (LHRH).

    Science.gov (United States)

    Obayemi, J D; Dozie-Nwachukwu, S; Danyuo, Y; Odusanya, O S; Anuku, N; Malatesta, K; Soboyejo, W O

    2015-01-01

    This paper presents the results of an experimental study of the biosynthesis of magnetite nanoparticles (BMNPs) with particle sizes between 10 nm and 60 nm. The biocompatible magnetic nanoparticles are produced from Magnetospirillum magneticum (M.M.) bacteria that respond to magnetic fields. M.M. bacteria were cultured and used to synthesize magnetite nanoparticles. This was done in an enriched magnetic spirillum growth medium (EMSGM) at different pH levels. The nanoparticle concentrations were characterized with UV-Visible (UV-Vis) spectroscopy, while the particle shapes were elucidated via transmission electron microscopy (TEM). The structure of the particles was studied using X-ray diffraction (XRD), while the hydrodynamic radii, particle size distributions and polydispersity of the nanoparticles were characterized using dynamic light scattering (DLS). Carbodiimide reduction was also used to functionalize the BMNPs with a molecular recognition unit (luteinizing hormone releasing hormone, LHRH) that attaches specifically to receptors that are over-expressed on the surfaces of most breast cancer cell types. The resulting nanoparticles were examined using Fourier Transform Infrared (FTIR) spectroscopy and quantitative image analysis. The implications of the results are then discussed for the potential development of magnetic nanoparticles for the specific targeting and treatment of breast cancer.

  9. Photoemission electron microscopy and scanning electron microscopy of Magnetospirillum magnetotacticum’s magnetosome chains

    Energy Technology Data Exchange (ETDEWEB)

    Keutner, Christoph [Technische Univ. Dortmund, Dortmung (Germany); von Bohlen, Alex [Leibniz-Institut fur Analytische Wissenschaften, Dortmund (Germany); Berges, Ulf [Technische Univ. Dortmund, Dortmung (Germany); Espeter, Philipp [Technische Univ. Dortmund, Dortmung (Germany); Schneider, Claus M. [Peter Grunberg Institut, Julich (Germany); Westphal, Carsten [Technische Univ. Dortmund, Dortmung (Germany)

    2014-10-07

    Magnetotactic bacteria are of great interdisciplinary interest, since a vast field of applications from magnetic recording media to medical nanorobots is conceivable. A key feature for a further understanding is the detailed knowledge about the magnetosome chain within the bacteria. We report on two preparation procedures suitable for UHV experiments in reflective geometry. Further, we present the results of scanning electron microscopy, as well as the first photoemission electron microscopy experiments, both accessing the magnetosomes within intact magnetotactic bacteria and compare these to scanning electron microscopy data from the literature. From the images, we can clearly identify individual magnetosomes within their chains.

  10. Microbial sulfide oxidation in the oxic–anoxic transition zone of freshwater sediment: involvement of lithoautotrophic Magnetospirillum strain J10

    NARCIS (Netherlands)

    Geelhoed, J.S.; Sorokin, D.; Epping, E.; Tourova, T.P.; Banciu, H.L.; Muyzer, G.; Stams, A.J.M.; Loosdrecht, van M.C.

    2009-01-01

    The oxic-anoxic transition zone (OATZ) of freshwater sediments, where opposing gradients exist of reduced iron and sulfide with oxygen, creates a suitable environment for microorganisms that derive energy from the oxidation of iron or sulfide. Gradient microcosms incubated with freshwater sediment

  11. Effects of Dissolved Oxygen Concentration and Iron Addition on Immediate-early Gene Expression of Magnetospirillum gryphiswaldense MSR-1

    DEFF Research Database (Denmark)

    Zhuang, Shiwen; Anyaogu, Diana Chinyere; Kasama, Takeshi

    2017-01-01

    iron addition for all the genes studied, except for MgFnr (oxygen sensor gene) and fur (ferric uptake regulator family gene), and which in some cases was oxygen-dependent. In particular, expression of sodB1 (superoxide dismutase gene) and feoB1 (ferrous transport protein B1 gene) were markedly reduced...... in cultures at 0.5% O2 compared to those at higher oxygen tensions. Moreover, expression of katG (catalase-peroxidase gene) and feoB2 (ferrous transport protein B2 gene) was reduced markedly by iron addition, regardless of oxygen conditions. The data provides a greater understanding of molecular response...

  12. Statistical approach for the culture conditions optimization of magnetotactic bacteria for magnetic cells production

    Institute of Scientific and Technical Information of China (English)

    Li Wenbing; Yu Longjiang; Zhou Pengpeng

    2006-01-01

    The culture of Magnetospirillum magneticum WM-1 depends on several control factors that have great effect on the magnetic cells concentration. Investigation into the optimal culture conditions needs a large number of experiments. So it is desirable to minimize the number of experiments and maximize the information gained from them. The orthogonal design of experiments and mathematical statistical method are considered as effective methods to optimize the culture condition of magnetotactic bacteria WM-1 for high magnetic cells concentration. The effects of the four factors, such as pH value of medium, oxygen concentration of gas phase in the serum bottle, C:C (mtartaric acid: msuccinic acid) ratio and NaNO3 concentration, are simultaneously investigated by only sixteen experiments through the orthogonal design L16(44) method. The optimal culture condition is obtained. At the optimal culture condition ( pH 7.0, an oxygen concentration 4.0%, C: C (mtartaric acid:msuccinic acid) ratio 1:2 and NaNO3 100 mg l-1), the magnetic cells concentration is promoted to 6.5×107 cells ml-1, approximately 8.3% higher than that under the initial conditions. The pH value of medium is a very important factor for magnetic cells concentration. It can be proved that the orthogonal design of experiment is of 90% confidence. Ferric iron uptake follows Michaelis-Menten kinetics with a Km of 2.5 μM and a Vmax of 0.83 min-1.

  13. Biosynthesis and the conjugation of magnetite nanoparticles with luteinizing hormone releasing hormone (LHRH)

    Energy Technology Data Exchange (ETDEWEB)

    Obayemi, J.D. [Department of Materials Science and Engineering, African University of Science and Technology (AUST) Abuja, Federal Capital Territory (Nigeria); Department of Materials Science and Engineering, Kwara State University, Malete, Kwara State (Nigeria); Dozie-Nwachukwu, S. [Department of Materials Science and Engineering, African University of Science and Technology (AUST) Abuja, Federal Capital Territory (Nigeria); Sheda Science and Technology Complex (SHESTCO) Abuja, Federal Capital Territory (Nigeria); Danyuo, Y. [Department of Materials Science and Engineering, African University of Science and Technology (AUST) Abuja, Federal Capital Territory (Nigeria); Department of Electronics and Electricals Engineering, Nigerian Turkish Nile University, Abuja (Nigeria); Odusanya, O.S. [Department of Materials Science and Engineering, African University of Science and Technology (AUST) Abuja, Federal Capital Territory (Nigeria); Sheda Science and Technology Complex (SHESTCO) Abuja, Federal Capital Territory (Nigeria); Anuku, N. [Department of Chemistry, Bronx Community College, New York, NY 10453 (United States); Princeton Institute of Science and Technology of Materials (PRISM), Princeton, NJ 08544 (United States); Malatesta, K. [Princeton Institute of Science and Technology of Materials (PRISM), Princeton, NJ 08544 (United States); Department of Mechanical and Aerospace Engineering, Princeton University, NJ 08544 (United States); Soboyejo, W.O., E-mail: soboyejo@princeton.edu [Department of Materials Science and Engineering, African University of Science and Technology (AUST) Abuja, Federal Capital Territory (Nigeria); Princeton Institute of Science and Technology of Materials (PRISM), Princeton, NJ 08544 (United States); Department of Mechanical and Aerospace Engineering, Princeton University, NJ 08544 (United States)

    2015-01-01

    This paper presents the results of an experimental study of the biosynthesis of magnetite nanoparticles (BMNPs) with particle sizes between 10 nm and 60 nm. The biocompatible magnetic nanoparticles are produced from Magnetospirillum magneticum (M.M.) bacteria that respond to magnetic fields. M.M. bacteria were cultured and used to synthesize magnetite nanoparticles. This was done in an enriched magnetic spirillum growth medium (EMSGM) at different pH levels. The nanoparticle concentrations were characterized with UV–Visible (UV–Vis) spectroscopy, while the particle shapes were elucidated via transmission electron microscopy (TEM). The structure of the particles was studied using X-ray diffraction (XRD), while the hydrodynamic radii, particle size distributions and polydispersity of the nanoparticles were characterized using dynamic light scattering (DLS). Carbodiimide reduction was also used to functionalize the BMNPs with a molecular recognition unit (luteinizing hormone releasing hormone, LHRH) that attaches specifically to receptors that are over-expressed on the surfaces of most breast cancer cell types. The resulting nanoparticles were examined using Fourier Transform Infrared (FTIR) spectroscopy and quantitative image analysis. The implications of the results are then discussed for the potential development of magnetic nanoparticles for the specific targeting and treatment of breast cancer. - Highlights: • Biosynthesis of MNPs with clinically relevant sizes between 10 and 60 nm. • New insights into the effects of pH and processing time on nanoparticle shapes and sizes. • Successful conjugation of biosynthesized magnetite nanoparticles to LHRH ligands. • Conjugated BMNPs that are monodispersed with potential biomedical relevance. • Magnetic properties of biosynthesized MNPs suggest potential for MRI enhancement.

  14. Isolation and characterization of Magnetospirillum sp strain 15-1 as a representative anaerobic toluene-degrader from a constructed wetland model

    DEFF Research Database (Denmark)

    Meyer-Cifuentes, Ingrid; Lavanchy, Paula Maria Martinez; Marin-Cevada, Vianey

    2017-01-01

    Previously, Planted Fixed-Bed Reactors (PFRs) have been used to investigate microbial toluene removal in the rhizosphere of constructed wetlands. Aerobic toluene degradation was predominant in these model systems although bulk redox conditions were hypoxic to anoxic. However, culture...

  15. Cloning and functional analysis of the sequences flanking mini-Tn5 in the magnetosome-deleted mutant NM21 of Magnetospirillum gryphiswaldense MSR-1

    Institute of Scientific and Technical Information of China (English)

    LI Feng; LI Ying; JIANG Wei; WANG ZhenFang; LI JiLun

    2009-01-01

    A magnetosome-deleted mutant NM21 of MagnetospMIlum gryphiswaldense MSR-1 was generated by mini-Tn5 lacZ2 transposon mutagenesis, and a 3073-bp fragment flanking mini-Tn5 lacZ2 in NM21 was cloned by Anchored PCR. Sequencing analysis showed that this fragment involved three putative ORFs; the mini-Tn5 lacZ2 was inserted into ORF1. Functional complementary test indicated that the 3073-bp fragment was required for biosynthesis of magnetosomes in M. gryphiswaldense MSR-1. The majority of proteins, which bad homology with the protein encoded by ORF1, were the cation transporter. Transmembrane domain analysis showed that the protein encoded by ORF1 contained four trans-membrane domains. It may be a transmembrane protein. The protein encoded by ORF1 contained two putative conserved domains: COG0053 and PRK09509. The MMT1 and FieF, containing conserved domains COG0053 and PRK09509 too, were Fe2+ transporter (cation diffusion facilitator superfamily). It was suggested that the protein encoded by ORF1 might take part in the magnetosomes biosynthesis as Fe2+ transporter.

  16. Gene : CBRC-OANA-01-2144 [SEVENS

    Lifescience Database Archive (English)

    Full Text Available protein [Magnetospirillum gryphiswaldense MSR-1] 1e-10 45% gnl|UG|Oan#S38869732 PREDICTED: Ornithorhynchus anatinus similar to repul...sive guidance molecule C, RgmC protein (LOC100074217), mRNA /cds=p(1,3762) /gb=XM_0

  17. Dicty_cDB: Contig-U11414-1 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available ecticidal tox... 77 2e-12 AP007255_1841( AP007255 |pid:none) Magnetospirillum magne... CP000448_360( CP000448 |pid:none) Syntrophomonas wolfei subsp. wol... 77 2e-12 DQ400808_1( DQ400808 |pid:none) Yersinia sp. MH-1 ins

  18. Detection of endogenous magnetic nanoparticles with a tunnelling magneto resistance sensor.

    Science.gov (United States)

    Ionescu, A; Darton, N J; Vyas, K; Llandro, J

    2010-09-28

    The magnetotactic bacterium Magnetospirillum sp. has been cultured and the properties of its endogenous magnetic nanoparticles characterized. Electron-microscopic analyses indicate that the endogenous magnetite nanoparticles in Magnetospirillum sp. are coated with a 3-4 nm thick transparent shell, forming a magnetosome. These magnetite nanoparticles had diameters of 50.9+/-13.3 nm, in good agreement with the diameter of 40.6+/-1.2 nm extracted from magnetometry. Each Magnetospirillum sp. bacterium contained chains of 5-25 magnetosomes. Superconducting quantum interference device magnetometry results indicate that the extrinsic superparamagnetic response of the bacterial solution at room temperature can be attributed to the reversal of the magnetization by physical rotation of the nanoparticles. The intrinsic blocking temperature of a sample of freeze-dried bacteria was estimated to be 282+/-13 K. A tunnelling magneto resistance sensor was used to detect the stray fields of endogenous magnetic nanoparticles in static and quasi-dynamic modes. Based on the tunnelling magneto resistance sensor results, the magnetic moment per bacterium was estimated to be approximately 2.6 x 10(-13) emu. The feasibility of this detection method either as a mass-coverage device or as part of an integrated microfluidic circuit for detection and sorting of magnetosome-containing cells was demonstrated.

  19. Calculational Investigation for Mine-Clearance Experiments

    Science.gov (United States)

    1981-08-31

    Charge Calculation LFT7 Dese ir p= 10 k/m310 lb/ft Charge AMB1IENT AIR Ojrn FIGURE 17. SAP Problem 5.0013 Initial Mesh Configuration 3’ zones of air...LI co OCO -c i C 0 *Lt’ 3d ) 0as~ a a 4)45 I I I I ~14-~ 12 Problem 5.0008 S10 Ii aa I 044 Qiý4 4 0 I 2- 7,Ref lected Shock Brief Negative Phase 0 2 4

  20. Isolation and characterization of Reyranella massiliensis gen. nov., sp. nov. from freshwater samples by using an amoeba co-culture procedure.

    Science.gov (United States)

    Pagnier, Isabelle; Raoult, Didier; La Scola, Bernard

    2011-09-01

    The analysis of three water samples from two cooling towers and one river allowed us to isolate three strains of a novel species of the class Alphaproteobacteria which is phylogenetically related to uncultured alphaproteobacteria. Based upon 16S rRNA gene sequence analysis and phenotypic characterization, we propose to name this novel species Reyranella massiliensis gen. nov., sp. nov., type strain 521(T) ( = CSUR P115(T)  = DSM 23428(T)). The most closely related cultivable micro-organism to this novel bacterium is a member of the genus Magnetospirillum.

  1. AcEST: BP914389 [AcEST

    Lifescience Database Archive (English)

    Full Text Available RIVAREDDEAYGRL 173 TrEMBL (release 39.9) Link to BlastX Result : TrEMBL tr_hit_id Q2W0W4 Definition tr|Q2W0W4|Q2W0W4_MAGMM Aerobic...ces producing significant alignments: (bits) Value tr|Q2W0W4|Q2W0W4_MAGMM Aerobic... ... 33 8.1 >tr|Q2W0W4|Q2W0W4_MAGMM Aerobic-type carbon monoxide dehydrogenase OS=Magnetospirillum magneticu

  2. Liposomal amphotericin B dry powder inhaler: effect of fines on in vitro performance.

    Science.gov (United States)

    Shah, S P; Misra, A

    2004-10-01

    The aim of the present investigation was to improve in vitro pulmonary deposition of amphotericin B (AMB) liposomal dry powder inhaler (LDPI) formulations. Liposomes with negative (AMB1) and positive (AMB2) charge were prepared by the reverse phase evaporation (REV) technique, extruded to reduce size, separated from unentrapped drug and lyophilized using an optimized cryoprotectant to achieve maximum drug retention. Lactose carrier (Sorbolac 400) in varying mass ratio with or without addition of fines (500# sieved Pharmatose 325M) in different mixing sequence were used to formulate AMB LDPI formulations. In vitro evaluation was done with twin stage impinger (TSI) for fine particle fraction. The lactose carrier containing 10% fines was found to be optimum blend at 1:6 mass ratio of liposome: lactose. The addition of fines and order of mixing fines were found to influence the fine particle fraction (FPF) significantly. FPF of LDPI formulations using a Rotahaler (Cipla, India) as delivery device at 30, 60 and 90 L/min were found to be 23.1 +/- 1.5 percent and 17.3 +/- 2.2 percent; 25.3 +/- 1.8 percent and 19.6 +/- 1.5 percent and 28.4 +/- 2.1 percent and 22.9 +/- 1.9 percent for AMB1 and AMB2 respectively.

  3. High-Sensitivity Detection of Fruit Tree Viruses Using Bacterial Magnetic Particles

    Institute of Scientific and Technical Information of China (English)

    Ji-Feng Chen; Ying Li; Zhen-Fang Wang; Ji-Lun Li; Wei Jiang; Shao-Hua Li

    2009-01-01

    Prunus necrotic ring spot virus (PNRSV) and grapevine fanleaf virus (GFLV) were detected by fluoroimmunoassay using bacterial magnetic particles (BMPs),and a double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA).For the fluoroimmunoassay,fluorescein isothiocyanate labeled anti-PNRSV antibody or anti-GFLV antibody was conjugated onto BMPs of Magnetospirillum gryphiswaldense MSR-I.With this method,a very low minimum antigen concentration (1 x 106 dilution of the original sample concentration) could be detected.Using DAS-ELISA,the minimum antigen detection concentration was the original sample concentration.Thus,comparing these two methods,a BMP-based method could increase the sensitivity up to six orders of magnitude (106) higher than an ELISA-based method of detection PNRSV and GFLV.

  4. Preliminary evaluation of nanoscale biogenic magnetite-based ferromagnetic transduction mechanisms for mobile phone bioeffects.

    Science.gov (United States)

    Cranfield, Charles; Wieser, Heinz Gregor; Al Madan, Jaffar; Dobson, Jon

    2003-03-01

    Ferromagnetic transduction models have been proposed as a potential mechanism for mobile phone bioeffects. These models are based on the coupling of RF and pulsed electromagnetic emissions to biogenic magnetite (Fe3O4) present in the human brain via either ferromagnetic resonance or mechanical activation of cellular ion channels. We have tested these models experimentally for the first time using a bacterial analogue (Magnetospirillum magnetotacticum) which produces intracellular biogenic magnetite similar to that present in the human brain. Experimental evaluation revealed that exposure to mobile phone emissions resulted in a consistent and significantly higher proportion of cell death in exposed cultures versus sham exposure (p = 0.037). Though there appears to be a repeatable trend toward higher cell mortality in magnetite-producing bacteria exposed to mobile phone emissions, it is not yet clear that this would extrapolate to a deleterious health effect in humans.

  5. Antifungal activity of amphotericin B conjugated to carbon nanotubes.

    Science.gov (United States)

    Benincasa, Monica; Pacor, Sabrina; Wu, Wei; Prato, Maurizio; Bianco, Alberto; Gennaro, Renato

    2011-01-25

    Amphotericin B (AMB) has long been considered the most effective drug in the treatment of serious invasive fungal infections. There are, however, major limitations to its use, due to several adverse effects, including acute infusional reactions and, most relevant, a dose-dependent nephrotoxicity. At least some of these effects are attributed to the aggregation of AMB as a result of its poor water solubility. To overcome this problem, reformulated versions of the drug have been developed, including a micellar dispersion of AMB with sodium deoxycholate (AMBD), its encapsulation into liposomes, or its incorporation into lipidic complexes. The development of nanobiotechnologies provides novel potential drug delivery systems that make use of nanomaterials such as functionalized carbon nanotubes (f-CNTs), which are emerging as an innovative and efficient tool for the transport and cellular translocation of therapeutic molecules. In this study, we prepared two conjugates between f-CNTs and AMB. The antifungal activity of these conjugates was tested against a collection of reference and clinical fungal strains, in comparison to that of AMB alone or AMBD. Measured minimum inhibition concentration (MIC) values for f-CNT-AMB conjugates were either comparable to or better than those displayed by AMB and AMBD. Furthermore, AMBD-resistant Candida strains were found to be susceptible to f-CNT-AMB 1. Additional studies, aimed at understanding the mechanism of action of the conjugates, suggest a nonlytic mechanism, since the compounds show a major permeabilizing effect on the tested fungal strains only after extended incubation. Interestingly, the f-CNT-AMB 1 does not show any significant toxic effect on Jurkat cells at antifungal concentrations.

  6. Biogenesis of actin-like bacterial cytoskeletal filaments destined for positioning prokaryotic magnetic organelles.

    Science.gov (United States)

    Pradel, Nathalie; Santini, Claire-Lise; Bernadac, Alain; Fukumori, Yoshihiro; Wu, Long-Fei

    2006-11-14

    Magnetosomes comprise a magnetic nanocrystal surrounded by a lipid bilayer membrane. These unique prokaryotic organelles align inside magnetotactic bacterial cells and serve as an intracellular compass allowing the bacteria to navigate along the geomagnetic field in aquatic environments. Cryoelectron tomography of Magnetospirillum strains has revealed that the magnetosome chain is surrounded by a network of filaments that may be composed of MamK given that the filaments are absent in the mamK mutant cells. The process of the MamK filament assembly is unknown. Here we prove the authenticity of the MamK filaments and show that MamK exhibits linear distribution inside Magnetospirillum sp. cells even in the area without magnetosomes. The mamK gene alone is sufficient to direct the synthesis of straight filaments in Escherichia coli, and one extremity of the MamK filaments is located at the cellular pole. By using dual fluorescent labeling of MamK, we found that MamK nucleates at multiple sites and assembles into mosaic filaments. Time-lapse experiments reveal that the assembly of the MamK filaments is a highly dynamic and kinetically asymmetrical process. MamK bundles might initiate the formation of a new filament or associate to one preexistent filament. Our results demonstrate the mechanism of biogenesis of prokaryotic cytoskeletal filaments that are structurally and functionally distinct from the known MreB and ParM filaments. In addition to positioning magnetosomes, other hypothetical functions of the MamK filaments in magnetotaxis might include anchoring magnetosomes and being involved in magnetic reception.

  7. Interplay of magnetic interactions and active movements in the formation of magnetosome chains.

    Directory of Open Access Journals (Sweden)

    Stefan Klumpp

    Full Text Available Magnetotactic bacteria assemble chains of magnetosomes, organelles that contain magnetic nano-crystals. A number of genetic factors involved in the controlled biomineralization of these crystals and the assembly of magnetosome chains have been identified in recent years, but how the specific biological regulation is coordinated with general physical processes such as diffusion and magnetic interactions remains unresolved. Here, these questions are addressed by simulations of different scenarios for magnetosome chain formation, in which various physical processes and interactions are either switched on or off. The simulation results indicate that purely physical processes of magnetosome diffusion, guided by their magnetic interactions, are not sufficient for the robust chain formation observed experimentally and suggest that biologically encoded active movements of magnetosomes may be required. Not surprisingly, the chain pattern is most resembling experimental results when both magnetic interactions and active movement are coordinated. We estimate that the force such active transport has to generate is compatible with forces generated by the polymerization or depolymerization of cytoskeletal filaments. The simulations suggest that the pleiotropic phenotypes of mamK deletion strains may be due to a defect in active motility of magnetosomes and that crystal formation in magneteosome vesicles is coupled to the activation of their active motility in M. gryphiswaldense, but not in M. magneticum.

  8. On the linearity of tracer bias around voids

    CERN Document Server

    Pollina, Giorgia; Dolag, Klaus; Weller, Jochen; Baldi, Marco; Moscardini, Lauro

    2016-01-01

    The large-scale structure of the universe can only be observed directly via luminous tracers of the underlying distribution of dark matter. However, the clustering statistics of tracers are biased and depend on various properties of the tracers themselves, such as their host-halo mass and formation and assembly history. On very large scales, where density fluctuations are within the linear regime, this tracer bias results in a constant offset in the clustering amplitude, which is known as linear bias. Towards smaller non-linear scales, this is no longer the case and tracer bias becomes a complicated function of scale and time. We focus on tracer bias centered on cosmic voids, depressions of the density field that spatially dominate the universe. We consider three different types of tracers: galaxies, galaxy clusters and AGNs, extracted from the hydrodynamical simulation suite Magneticum Pathfinder. In contrast to common clustering statistics that focus on the auto-correlation of tracers, we find that void-tra...

  9. A "Universal" Density Profile for the Outer Stellar Halos of Galaxies

    CERN Document Server

    Remus, Rhea-Silvia; Dolag, Klaus

    2016-01-01

    The outer stellar halos of galaxies contain vital information about the formation history of galaxies, since the relaxation timescales in the outskirts are long enough to keep the memory, while the information about individual formation events in the central parts has long been lost due to mixing, star formation and relaxation. To unveil some of the information encoded in these faint outer halo regions, we study the stellar outskirts of galaxies selected from a fully hydrodynamical high resolution cosmological simulation, called Magneticum. We find that the density profiles of the outer stellar halos of galaxies over a broad mass range can be well described by an Einasto profile. For a fixed total mass range, the free parameters of the Einasto fits are closely correlated. Galaxies which had more (dry) merger events tend to have lesser curved outer stellar halos, however, we find no indication that the amount of curvature is correlated with galaxy morphology. The Einasto-like shape of the outer stellar halo de...

  10. Amphotericin B induced interdigitation of apolipoprotein stabilized nanodisk bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Nguyen, T; Weers, P M; Sulchek, T; Hoeprich, P D; Ryan, R O

    2006-12-07

    Amphotericin B nanodisks (AMB-ND) are ternary complexes of AMB, phospholipid (PL) and apolipoprotein organized as discrete nanometer scale disk-shaped bilayers. In gel filtration chromatography experiments, empty ND lacking AMB elute as a single population of particles with a molecular weight in the range of 200 kDa. AMB-ND formulated at a 4:1 PL:AMB weight ratio, separated into two peaks. Peak 1 eluted at the position of control ND lacking AMB while the second peak, containing all of the AMB present in the original sample, eluted in the void volume. When ND prepared with increased AMB (1:1 phospholipid:AMB molar ratio) were subjected to gel filtration chromatography, an increased proportion of phospholipid and apolipoprotein were recovered in the void volume with the AMB. Prior to gel filtration the AMB-ND sample could be passed through a 0.22 {micro}m filter without loss of AMB while the voided material was lost. Native gel electrophoresis studies corroborated the gel permeation chromatography data. Far UV circular dichroism analyses revealed that apoA-I associated with AMB-ND denatures at a lower guanidine HCl concentration than apoA-I associated with ND lacking AMB. Atomic force microscopy revealed that AMB induces compression of the ND bilayer thickness consistent with bilayer interdigitation, a phenomenon that is likely related to the ability of AMB to induce pore formation in susceptible membranes.

  11. [Molecular diversity of arbuscular mycorrhizal fungi in wild and cultured Gynostemma pentaphyllum roots in Xishuangbanna, Southwest China].

    Science.gov (United States)

    Zhou, Li-Si; Guo, Shun-Xing

    2013-09-01

    By using nested-PCR, DNA cloning, and sequencing techniques, this paper studied the diversity of the community structure of arbuscular mycorrhizal fungi (AMF) in wild and cultured Gynostemma pentaphyllum roots. A total of 551 clones containing 18S rDNA genes of AMF were obtained from the roots. After the analysis of the restriction fragment length polymorphism, 100 different RFLP types were obtained, which were further divided into 20 AMF phylotypes belonging to seven families. The comparison of the sequences of 20 AMF phylotypes with the GenBank database showed that there were 5 AMF phylotypes having high similarity to the sequences of reported AMF species Glomus viscosum, Claroideoglomus etunicatum, Racocetra tropicana, Acaulospora spinosa, and Acaulospora mellea, respectively. These sequences were then assessed for the similarities against the MaarjAM database, and 12 phylotypes showed high similarity to the corresponding molecular virtual taxa, of which, 7 phylotypes were not obtained by the morphological identification of soil asexual spores. Statistical analysis indicated that there were significant differences in the AMF community between wild and cultured G. pentaphyllum roots. The analysis of relative abundance data indicated that Glo-2, Amb-1, and Para-1 were the dominant phylotypes in wild G. pentaphyllum roots, while Glo-3, Glo-8, Glo-10, and Div-1 were the prevalent phylotypes in cultured ones. Claroideoglomeraceae and Ambisporaceae were only detected in wild G. pentaphyllum roots, and Diversisporaceae was only identified in cultured ones.

  12. A double-blind, randomized, controlled trial of amphotericin B colloidal dispersion versus amphotericin B for treatment of invasive aspergillosis in immunocompromised patients.

    Science.gov (United States)

    Bowden, Raleigh; Chandrasekar, Pranatharthi; White, Mary H; Li, Xin; Pietrelli, Larry; Gurwith, Marc; van Burik, Jo-Anne; Laverdiere, Michel; Safrin, Sharon; Wingard, John R

    2002-08-15

    We report a randomized, double-blind, multicenter trial in which amphotericin B colloidal dispersion (ABCD [Amphotec]; 6 mg/kg/day) was compared with amphotericin B (AmB; 1.0-1.5 mg/kg/day) for the treatment of invasive aspergillosis in 174 patients. For evaluable patients in the ABCD and AmB treatment groups, respective rates of therapeutic response (52% vs. 51%; P=1.0), mortality (36% vs. 45%; P=.4), and death due to fungal infection (32% vs. 26%; P=.7) were similar. Renal toxicity was lower (25% vs. 49%; P=.002) and the median time to onset of nephrotoxicity was longer (301 vs. 22 days; P<.001) in patients treated with ABCD. Rates of drug-related toxicity in patients receiving ABCD and AmB, respectively, were 53% versus 30% (chills), 27% versus 16% (fever), 1% versus 4% (hypoxia) and 22% versus 24% (toxicity requiring study drug discontinuation). ABCD appears to have equivalent efficacy and superior renal safety, compared with AmB, in the treatment of invasive aspergillosis. However, infusion-related chills and fever occurred more frequently in patients receiving ABCD than in those receiving AmB.

  13. Inter-phylum structural conservation of the magnetosome-associated TPR-containing protein, MamA.

    Science.gov (United States)

    Zeytuni, Natalie; Baran, Dror; Davidov, Geula; Zarivach, Raz

    2012-12-01

    Magnetotactic bacteria enclose the magnetosome, a unique prokaryotic sub-cellular organelle that allows the biomineralization of magnetic nano-crystals. Membrane-coated magnetosomes are arranged into a linear chain that permits magnetotactic bacteria to navigate geomagnetic fields. Magnetosome assembly and biomineralization are controlled by conserved magnetosome-associated proteins, including MamA, a tetra-trico-peptide repeat (TPR)-containing protein that was shown to coat the magnetosome membrane. In this study, two MamA structures from Candidatus Magnetobacterium bavaricum (Mbav) were determined via X-ray crystallography. These structures confirm that Mbav MamA folds as a sequential TPR protein and shares a high degree of structural similarity with homologous MamA proteins from Magnetospirillum species. Furthermore, the two TPR-containing domains of MamA are separated by an interphylum-conserved region containing a flexible hinge that is involved in ligand binding and recognition. Finally, substantial differences were found in the local stabilization of the MamA N-terminal domain as a result of the loss of an evolutionary conserved salt bridge.

  14. Properties of Magnetite Nanoparticles Produced by Magnetotactic Bacteria

    Institute of Scientific and Technical Information of China (English)

    LI Wenbing; YU Longjiang; ZHOU Pengpeng; WANG Guanghua; XU Binfu; CHENG Zhengzai; XU Weiguo

    2014-01-01

    The magnetic nanoparticles (magnetite) were prepared through the fermentation of the Magnetospirillum strain WM-1 newly isolated by our group. The samples were characterized by TEM, SAED, XRD, rock magnetic analysis, and Mössbauer spectroscopy. TEM and SAED measurements showed that the magnetosomes formed by strain WM-1 were single crystallites of high perfection with a cubic spinel structure of magnetite. X-ray measurements also fitted very well with standard Fe3O4 reflections with an inverse spinel structure of the magnetite core. The size of crystal as calculated by the Debye-Scherrer’s equation was approximately 55 nm. Rock magnetic analysis showed WM-1 synthesized single-domain magnetite magnetosomes, which were arranged in the form of linear chain. The high delta ratio ((δFC/δZFC=4) supported the criteria of Moskowitz test that there were intact magnetosomes chains in cells. The Verwey transition occurred at 105 K that closed to stoochiometric magnetite in composition. These observations provided useful insights into the biomineralization of magnetosomes and properties of M. WM-1 and potential application of biogenic magnetite in biomaterials and biomagnetism.

  15. Assemblies of magnetite nanoparticles extracted from magnetotactic bacteria: A magnetic study

    Science.gov (United States)

    Huízar-Félix, A. M.; Muñoz, D.; Orue, I.; Magén, C.; Ibarra, A.; Barandiarán, J. M.; Muela, A.; Fdez-Gubieda, M. L.

    2016-02-01

    Self-assembly has emerged as a suitable technique for tuning the properties of nanoparticles. In this work, we report the self-assembly of magnetosomes assisted by an external magnetic field. The magnetosomes are magnetite nanoparticles biomineralized by magnetotactic bacteria Magnetospirillum gryphiswaldense. These nanoparticles present truncated cubo-octahedral morphology with a mean diameter of ≈36 nm and are surrounded by a lipid bilayer membrane with a thickness ≈2-4 nm. The use of the appropriate preparation conditions, such as initial colloidal concentration and magnetic fields applied during deposition allowed us to obtain very reproducible self-assembled 2D patterns. Homogeneous ensembles of magnetosomes onto silicon and carbon surfaces are composed of elongated structures in the form of wide chains that cover a large area of the substrates. Transmission electron microscopy image and off-axis electron holography showed the map of the stray magnetic fields produced by these assemblies. The induced magnetic anisotropy was analyzed by measuring the hysteresis loops of the assemblies at different angles in a magneto-optical Kerr effect magnetometer. The evolution of the coercive field and remanence verified the presence of well-defined patterns. The experimental results were analyzed on the based of a biaxial model.

  16. Structure prediction of magnetosome-associated proteins

    Directory of Open Access Journals (Sweden)

    Hila eNudelman

    2014-01-01

    Full Text Available Magnetotactic bacteria (MTB are Gram-negative bacteria that can navigate along geomagnetic fields. This ability is a result of a unique intracellular organelle, the magnetosome. These organelles are composed of membrane-enclosed magnetite (Fe3O4 or greigite (Fe3S4 crystals ordered into chains along the cell. Magnetosome formation, assembly and magnetic nano-crystal biomineralization are controlled by magnetosome-associated proteins (MAPs. Most MAP-encoding genes are located in a conserved genomic region – the magnetosome island (MAI. The MAI appears to be conserved in all MTB that were analyzed so far, although the MAI size and organization differs between species. It was shown that MAI deletion leads to a non-magnetic phenotype, further highlighting its important role in magnetosome formation. Today, about 28 proteins are known to be involved in magnetosome formation, but the structures and functions of most MAPs are unknown. To reveal the structure-function relationship of MAPs we used bioinformatics tools in order to build homology models as a way to understand their possible role in magnetosome formation. Here we present a predicted 3D structural models’ overview for all known Magnetospirillum gryphiswaldense strain MSR-1 MAPs.

  17. Polyphasic analysis of an Azoarcus-Leptothrix-dominated bacterial biofilm developed on stainless steel surface in a gasoline-contaminated hypoxic groundwater.

    Science.gov (United States)

    Benedek, Tibor; Táncsics, András; Szabó, István; Farkas, Milán; Szoboszlay, Sándor; Fábián, Krisztina; Maróti, Gergely; Kriszt, Balázs

    2016-05-01

    Pump and treat systems are widely used for hydrocarbon-contaminated groundwater remediation. Although biofouling (formation of clogging biofilms on pump surfaces) is a common problem in these systems, scarce information is available regarding the phylogenetic and functional complexity of such biofilms. Extensive information about the taxa and species as well as metabolic potential of a bacterial biofilm developed on the stainless steel surface of a pump submerged in a gasoline-contaminated hypoxic groundwater is presented. Results shed light on a complex network of interconnected hydrocarbon-degrading chemoorganotrophic and chemolitotrophic bacteria. It was found that besides the well-known hydrocarbon-degrading aerobic/facultative anaerobic biofilm-forming organisms (e.g., Azoarcus, Leptothrix, Acidovorax, Thauera, Pseudomonas, etc.), representatives of Fe(2+)-and Mn(2+)-oxidizing (Thiobacillus, Sideroxydans, Gallionella, Rhodopseudomonas, etc.) as well as of Fe(3+)- and Mn(4+)-respiring (Rhodoferax, Geobacter, Magnetospirillum, Sulfurimonas, etc.) bacteria were present in the biofilm. The predominance of β-Proteobacteria within the biofilm bacterial community in phylogenetic and functional point of view was revealed. Investigation of meta-cleavage dioxygenase and benzylsuccinate synthase (bssA) genes indicated that within the biofilm, Azoarcus, Leptothrix, Zoogloea, and Thauera species are most probably involved in intrinsic biodegradation of aromatic hydrocarbons. Polyphasic analysis of the biofilm shed light on the fact that subsurface microbial accretions might be reservoirs of novel putatively hydrocarbon-degrading bacterial species. Moreover, clogging biofilms besides their detrimental effects might supplement the efficiency of pump and treat systems.

  18. Switching of swimming modes in Magnetospirillium gryphiswaldense

    CERN Document Server

    Reufer, Mathias; Schwarz-Linek, Jana; Martinez, Vincent A; Morozov, Alexander N; Arlt, Jochen; Trubitsyn, Denis; Ward, Bruce; Poon, Wilson C K

    2013-01-01

    The microaerophilic magnetotactic bacterium Magnetospirillum gryphiswaldense swims along magnetic field lines using a single flagellum at each cell pole. It is believed that this magnetotactic behavior enables cells to seek optimal oxygen concentration with maximal efficiency. We analyse the trajectories of swimming M. gryphiswaldense cells in external magnetic fields larger than the earth's field, and show that each cell can switch very rapidly (in < 0.2 s) between a fast and a slow swimming mode. Close to a glass surface, a variety of trajectories was observed, from straight swimming that systematically deviates from field lines to various helices. A model in which fast (slow) swimming is solely due to the rotation of the trailing (leading) flagellum can account for these observations. We determined the magnetic moment of this bacterium using a new method, and obtained a value of (2.0 $\\pm$ 0.6) $\\times$ $10^{-16}$ Am$^2$. This value is found to be consistent with parameters emerging from quantitative fi...

  19. In vitro assembly of the bacterial actin protein MamK from ‘ Candidatus Magnetobacterium casensis’ in the phylum Nitrospirae

    Directory of Open Access Journals (Sweden)

    Aihua Deng

    2016-03-01

    Full Text Available ABSTRACT Magnetotactic bacteria (MTB, a group of phylogenetically diverse organisms that use their unique intracellular magnetosome organelles to swim along the Earth’s magnetic field, play important roles in the biogeochemical cycles of iron and sulfur. Previous studies have revealed that the bacterial actin protein MamK plays essential roles in the linear arrangement of magnetosomes in MTB cells belonging to the Proteobacteria phylum. However, the molecular mechanisms of multiple-magnetosome-chain arrangements in MTB remain largely unknown. Here, we report that the MamK filaments from the uncultivated ‘Candidatus Magnetobacterium casensis’ (Mcas within the phylum Nitrospirae polymerized in the presence of ATP alone and were stable without obvious ATP hydrolysis-mediated disassembly. MamK in Mcas can convert NTP to NDP and NDP to NMP, showing the highest preference to ATP. Unlike its Magnetospirillum counterparts, which form a single magnetosome chain, or other bacterial actins such as MreB and ParM, the polymerized MamK from Mcas is independent of metal ions and nucleotides except for ATP, and is assembled into well-ordered filamentous bundles consisted of multiple filaments. Our results suggest a dynamically stable assembly of MamK from the uncultivated Nitrospirae MTB that synthesizes multiple magnetosome chains per cell. These findings further improve the current knowledge of biomineralization and organelle biogenesis in prokaryotic systems.

  20. Subcellular localization of the magnetosome protein MamC in the marine magnetotactic bacterium Magnetococcus marinus strain MC-1 using immunoelectron microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Valverde-Tercedor, C [Universidad de Granada; Abada-Molina, F [Universidad de Granada; Martinez-Bueno, M [Universidad de Granada; Pineda-Molina, Estela [Laboratorio de Estudios Cristalograficos; Chen, Lijun [Ohio State University; Oestreicher, Zachery [Ohio State University; Lower, Brian H [Ohio State University; Lower, Steven K [Ohio State University; Bazylinski, Dennis A [Ames Laboratory; Jimenez-Lopez, C [Universidad de Granada

    2014-04-24

    Magnetotactic bacteria are a diverse group of prokaryotes that biomineralize intracellular magnetosomes, composed of magnetic (Fe3O4) crystals each enveloped by a lipid bilayer membrane that contains proteins not found in other parts of the cell. Although partial roles of some of these magnetosome proteins have been determined, the roles of most have not been completely elucidated, particularly in how they regulate the biomineralization process. While studies on the localization of these proteins have been focused solely on Magnetospirillum species, the goal of the present study was to determine, for the first time, the localization of the most abundant putative magnetosome membrane protein, MamC, in Magnetococcus marinus strain MC-1. MamC was expressed in Escherichia coli and purified. Monoclonal antibodies were produced against MamC and immunogold labeling TEM was used to localize MamC in thin sections of cells of M. marinus. Results show that MamC is located only in the magnetosome membrane of Mc. marinus. Based on our findings and the abundance of this protein, it seems likely that it is important in magnetosome biomineralization and might be used in controlling the characteristics of synthetic nanomagnetite.

  1. On the linearity of tracer bias around voids

    Science.gov (United States)

    Pollina, Giorgia; Hamaus, Nico; Dolag, Klaus; Weller, Jochen; Baldi, Marco; Moscardini, Lauro

    2017-07-01

    The large-scale structure of the Universe can be observed only via luminous tracers of the dark matter. However, the clustering statistics of tracers are biased and depend on various properties, such as their host-halo mass and assembly history. On very large scales, this tracer bias results in a constant offset in the clustering amplitude, known as linear bias. Towards smaller non-linear scales, this is no longer the case and tracer bias becomes a complicated function of scale and time. We focus on tracer bias centred on cosmic voids, i.e. depressions of the density field that spatially dominate the Universe. We consider three types of tracers: galaxies, galaxy clusters and active galactic nuclei, extracted from the hydrodynamical simulation Magneticum Pathfinder. In contrast to common clustering statistics that focus on auto-correlations of tracers, we find that void-tracer cross-correlations are successfully described by a linear bias relation. The tracer-density profile of voids can thus be related to their matter-density profile by a single number. We show that it coincides with the linear tracer bias extracted from the large-scale auto-correlation function and expectations from theory, if sufficiently large voids are considered. For smaller voids we observe a shift towards higher values. This has important consequences on cosmological parameter inference, as the problem of unknown tracer bias is alleviated up to a constant number. The smallest scales in existing data sets become accessible to simpler models, providing numerous modes of the density field that have been disregarded so far, but may help to further reduce statistical errors in constraining cosmology.

  2. Redshift-space distortions of galaxies, clusters, and AGN. Testing how the accuracy of growth rate measurements depends on scales and sample selections

    Science.gov (United States)

    Marulli, Federico; Veropalumbo, Alfonso; Moscardini, Lauro; Cimatti, Andrea; Dolag, Klaus

    2017-03-01

    Aims: Redshift-space clustering anisotropies caused by cosmic peculiar velocities provide a powerful probe to test the gravity theory on large scales. However, to extract unbiased physical constraints, the clustering pattern has to be modelled accurately, taking into account the effects of non-linear dynamics at small scales, and properly describing the link between the selected cosmic tracers and the underlying dark matter field. Methods: We used a large hydrodynamic simulation to investigate how the systematic error on the linear growth rate, f, caused by model uncertainties, depends on sample selections and co-moving scales. Specifically, we measured the redshift-space two-point correlation function of mock samples of galaxies, galaxy clusters and active galactic nuclei, extracted from the Magneticum simulation, in the redshift range 0.2 ≤ z ≤ 2, and adopting different sample selections. We estimated fσ8 by modelling both the monopole and the full two-dimensional anisotropic clustering, using the dispersion model. Results: We find that the systematic error on fσ8 depends significantly on the range of scales considered for the fit. If the latter is kept fixed, the error depends on both redshift and sample selection due to the scale-dependent impact of non-linearities if not properly modelled. Concurrently, we show that it is possible to achieve almost unbiased constraints on fσ8 provided that the analysis is restricted to a proper range of scales that depends non-trivially on the properties of the sample. This can have a strong impact on multiple tracer analyses, and when combining catalogues selected at different redshifts.

  3. Sporothrix schenckii complex in Iran: Molecular identification and antifungal susceptibility.

    Science.gov (United States)

    Mahmoudi, Shahram; Zaini, Farideh; Kordbacheh, Parivash; Safara, Mahin; Heidari, Mansour

    2016-08-01

    Sporotrichosis is a global subcutaneous fungal infection caused by the Sporothrix schenckii complex. Sporotrichosis is an uncommon infection in Iran, and there have been no phenotypic, molecular typing or antifungal susceptibility studies of Sporothrix species. This study aimed to identify nine Iranian isolates of the S. schenckii complex to the species level using colony morphology, carbohydrate assimilation tests, and PCR-sequencing of the calmodulin gene. The antifungal susceptibilities of these Sporothrix isolates to five antifungal agents (amphotericin B (AMB), voriconazole (VRC), itraconazole (ITC), fluconazole (FLC), and terbinafine (TRB)) were also evaluated according to the M27-A3 and M38-A2 protocols of the Clinical and Laboratory Standards Institute for yeast and mycelial phases, respectively. Five of seven clinical isolates were identified as S. schenckii, and two clinical and two environmental isolates were identified as S. globosa. This is the first report of S. globosa in Iran. There was significant agreement (73%) between the results of the phenotypic and genotypic identification methods. TRB and ITC were the most effective antifungals against the Sporothrix isolates. The minimum inhibitory concentration (MIC) values of TRB for the yeast and mycelial phases of S. schenckii differed significantly. There was also a significant difference in the minimum fungicidal concentration (MFC) values of AMB and TRB for the two phases. Considering the low efficacy of VRC and FLC and the wide MIC ranges of AMB (1-16 μg/ml and 1-8 μg/ml for yeast and mycelial forms, respectively) observed in the present study, in vitro antifungal susceptibility testing should be performed to determine appropriate therapeutic regimens.

  4. Composted Cattle Manure Increases Microbial Activity and Soil Fertility More Than Composted Swine Manure in a Submerged Rice Paddy

    Directory of Open Access Journals (Sweden)

    Suvendu Das

    2017-09-01

    Full Text Available Livestock waste composts with minimum inorganic fertilizer as a soil amendment in low-input intensive farming are a feasible agricultural practice to improve soil fertility and productivity and to mitigate soil degradation. The key benefits of the practice rely on the activities of soil microorganisms. However, the role of different livestock composts [composted cattle manure (CCM vs. composted swine manure (CSM] on soil microbes, their activities and the overall impact on soil fertility and productivity in a flooded paddy remains elusive. This study compares the effectiveness of CCM and CSM amendment on bacterial communities, activities, nutrient availability, and crop yield in a flooded rice cropping system. We used deep 16S amplicon sequencing and soil enzyme activities to decipher bacterial communities and activities, respectively. Both CCM and CSM amendment significantly increased soil pH, nutrient availability (C, N, and P, microbial biomass, soil enzyme activities indicative for C and N cycles, aboveground plant biomass and grain yield. And the increase in above-mentioned parameters was more prominent in the CCM treatment compared to the CSM treatment. The CCM amendment increased species richness and stimulated copiotrophic microbial groups (Alphaproteobacteria, Betaproteobacteria, and Firmicutes which are often involved in degradation of complex organic compounds. Moreover, some dominant species (e.g., Azospirillum zeae, Azospirillum halopraeferens, Azospirillum rugosum, Clostridium alkalicellulosi, Clostridium caenicola, Clostridium termitidis, Clostridium cellulolyticum, Magnetospirillum magnetotacticum, Pleomorphomonas oryzae, Variovorax boronicumulans, Pseudomonas xanthomarina, Pseudomonas stutzeri, and Bacillus niacini which have key roles in plant growth promotion and/or lignocellulose degradation were enhanced under CCM treatment compared to CSM treatment. Multivariate analysis revealed that soil pH and available carbon (C and

  5. Segregation of prokaryotic magnetosomes organelles is driven by treadmilling of a dynamic actin-like MamK filament.

    Science.gov (United States)

    Toro-Nahuelpan, Mauricio; Müller, Frank D; Klumpp, Stefan; Plitzko, Jürgen M; Bramkamp, Marc; Schüler, Dirk

    2016-10-12

    The navigation of magnetotactic bacteria relies on specific intracellular organelles, the magnetosomes, which are membrane-enclosed crystals of magnetite aligned into a linear chain. The magnetosome chain acts as a cellular compass, aligning the cells in the geomagnetic field in order to search for suitable environmental conditions in chemically stratified water columns and sediments. During cytokinesis, magnetosome chains have to be properly positioned, cleaved and separated in order to be evenly passed into daughter cells. In Magnetospirillum gryphiswaldense, the assembly of the magnetosome chain is controlled by the actin-like MamK, which polymerizes into cytoskeletal filaments that are connected to magnetosomes through the acidic MamJ protein. MamK filaments were speculated to recruit the magnetosome chain to cellular division sites, thus ensuring equal organelle inheritance. However, the underlying mechanism of magnetic organelle segregation has remained largely unknown. Here, we performed in vivo time-lapse fluorescence imaging to directly track the intracellular movement and dynamics of magnetosome chains as well as photokinetic and ultrastructural analyses of the actin-like cytoskeletal MamK filament. We show that magnetosome chains undergo rapid intracellular repositioning from the new poles towards midcell into the newborn daughter cells, and the driving force for magnetosomes movement is likely provided by the pole-to-midcell treadmilling growth of MamK filaments. We further discovered that splitting and equipartitioning of magnetosome chains occurs with unexpectedly high accuracy, which depends directly on the dynamics of MamK filaments. We propose a novel mechanism for prokaryotic organelle segregation that, similar to the type-II bacterial partitioning system of plasmids, relies on the action of cytomotive actin-like filaments together with specific connectors, which transport the magnetosome cargo in a fashion reminiscent of eukaryotic actin

  6. Genetic and Ultrastructural Analysis Reveals the Key Players and Initial Steps of Bacterial Magnetosome Membrane Biogenesis

    Science.gov (United States)

    Kolinko, Isabel; Uebe, René; Schüler, Dirk

    2016-01-01

    Magnetosomes of magnetotactic bacteria contain well-ordered nanocrystals for magnetic navigation and have recently emerged as the most sophisticated model system to study the formation of membrane bounded organelles in prokaryotes. Magnetosome biosynthesis is thought to begin with the formation of a dedicated compartment, the magnetosome membrane (MM), in which the biosynthesis of a magnetic mineral is strictly controlled. While the biomineralization of magnetosomes and their subsequent assembly into linear chains recently have become increasingly well studied, the molecular mechanisms and early stages involved in MM formation remained poorly understood. In the Alphaproteobacterium Magnetospirillum gryphiswaldense, approximately 30 genes were found to control magnetosome biosynthesis. By cryo-electron tomography of several key mutant strains we identified the gene complement controlling MM formation in this model organism. Whereas the putative magnetosomal iron transporter MamB was most crucial for the process and caused the most severe MM phenotype upon elimination, MamM, MamQ and MamL were also required for the formation of wild-type-like MMs. A subset of seven genes (mamLQBIEMO) combined within a synthetic operon was sufficient to restore the formation of intracellular membranes in the absence of other genes from the key mamAB operon. Tracking of de novo magnetosome membrane formation by genetic induction revealed that magnetosomes originate from unspecific cytoplasmic membrane locations before alignment into coherent chains. Our results indicate that no single factor alone is essential for MM formation, which instead is orchestrated by the cumulative action of several magnetosome proteins. PMID:27286560

  7. Magnetic nanoparticles are highly toxic to chloroquine-resistant Plasmodium falciparum, dengue virus (DEN-2), and their mosquito vectors.

    Science.gov (United States)

    Murugan, Kadarkarai; Wei, Jiang; Alsalhi, Mohamad Saleh; Nicoletti, Marcello; Paulpandi, Manickam; Samidoss, Christina Mary; Dinesh, Devakumar; Chandramohan, Balamurugan; Paneerselvam, Chellasamy; Subramaniam, Jayapal; Vadivalagan, Chithravel; Wei, Hui; Amuthavalli, Pandiyan; Jaganathan, Anitha; Devanesan, Sandhanasamy; Higuchi, Akon; Kumar, Suresh; Aziz, Al Thabiani; Nataraj, Devaraj; Vaseeharan, Baskaralingam; Canale, Angelo; Benelli, Giovanni

    2017-02-01

    A main challenge in parasitology is the development of reliable tools to prevent or treat mosquito-borne diseases. We investigated the toxicity of magnetic nanoparticles (MNP) produced by Magnetospirillum gryphiswaldense (strain MSR-1) on chloroquine-resistant (CQ-r) and sensitive (CQ-s) Plasmodium falciparum, dengue virus (DEN-2), and two of their main vectors, Anopheles stephensi and Aedes aegypti, respectively. MNP were studied by Fourier-transform infrared spectroscopy and transmission electron microscopy. They were toxic to larvae and pupae of An. stephensi, LC50 ranged from 2.563 ppm (1st instar larva) to 6.430 ppm (pupa), and Ae. aegypti, LC50 ranged from 3.231 ppm (1st instar larva) to 7.545 ppm (pupa). MNP IC50 on P. falciparum were 83.32 μg ml(-1) (CQ-s) and 87.47 μg ml(-1) (CQ-r). However, the in vivo efficacy of MNP on Plasmodium berghei was low if compared to CQ-based treatments. Moderate cytotoxicity was detected on Vero cells post-treatment with MNP doses lower than 4 μg ml(-1). MNP evaluated at 2-8 μg ml(-1) inhibited DEN-2 replication inhibiting the expression of the envelope (E) protein. In conclusion, our findings represent the first report about the use of MNP in medical and veterinary entomology, proposing them as suitable materials to develop reliable tools to combat mosquito-borne diseases.

  8. The chemical formula of a magnetotactic bacterium.

    Science.gov (United States)

    Naresh, Mohit; Das, Sayoni; Mishra, Prashant; Mittal, Aditya

    2012-05-01

    Elucidation of the chemical logic of life is one of the grand challenges in biology, and essential to the progress of the upcoming field of synthetic biology. Treatment of microbial cells explicitly as a "chemical" species in controlled reaction (growth) environments has allowed fascinating discoveries of elemental formulae of a few species that have guided the modern views on compositions of a living cell. Application of mass and energy balances on living cells has proved to be useful in modeling of bioengineering systems, particularly in deriving optimized media compositions for growing microorganisms to maximize yields of desired bio-derived products by regulating intra-cellular metabolic networks. In this work, application of elemental mass balance during growth of Magnetospirillum gryphiswaldense in bioreactors has resulted in the discovery of the chemical formula of the magnetotactic bacterium. By developing a stoichiometric equation characterizing the formation of a magnetotactic bacterial cell, coupled with rigorous experimental measurements and robust calculations, we report the elemental formula of M. gryphiswaldense cell as CH(2.06)O(0.13)N(0.28)Fe(1.74×10(-3)). Remarkably, we find that iron metabolism during growth of this magnetotactic bacterium is much more correlated individually with carbon and nitrogen, compared to carbon and nitrogen with each other, indicating that iron serves more as a nutrient during bacterial growth rather than just a mineral. Magnetotactic bacteria have not only invoked some interest in the field of astrobiology for the last two decades, but are also prokaryotes having the unique ability of synthesizing membrane bound intracellular organelles. Our findings on these unique prokaryotes are a strong addition to the limited repertoire, of elemental compositions of living cells, aimed at exploring the chemical logic of life.

  9. Influence of magnetic fields on magneto-aerotaxis.

    Science.gov (United States)

    Bennet, Mathieu; McCarthy, Aongus; Fix, Dmitri; Edwards, Matthew R; Repp, Felix; Vach, Peter; Dunlop, John W C; Sitti, Metin; Buller, Gerald S; Klumpp, Stefan; Faivre, Damien

    2014-01-01

    The response of cells to changes in their physico-chemical micro-environment is essential to their survival. For example, bacterial magnetotaxis uses the Earth's magnetic field together with chemical sensing to help microorganisms move towards favoured habitats. The studies of such complex responses are lacking a method that permits the simultaneous mapping of the chemical environment and the response of the organisms, and the ability to generate a controlled physiological magnetic field. We have thus developed a multi-modal microscopy platform that fulfils these requirements. Using simultaneous fluorescence and high-speed imaging in conjunction with diffusion and aerotactic models, we characterized the magneto-aerotaxis of Magnetospirillum gryphiswaldense. We assessed the influence of the magnetic field (orientation; strength) on the formation and the dynamic of a micro-aerotactic band (size, dynamic, position). As previously described by models of magnetotaxis, the application of a magnetic field pointing towards the anoxic zone of an oxygen gradient results in an enhanced aerotaxis even down to Earth's magnetic field strength. We found that neither a ten-fold increase of the field strength nor a tilt of 45° resulted in a significant change of the aerotactic efficiency. However, when the field strength is zeroed or when the field angle is tilted to 90°, the magneto-aerotaxis efficiency is drastically reduced. The classical model of magneto-aerotaxis assumes a response proportional to the cosine of the angle difference between the directions of the oxygen gradient and that of the magnetic field. Our experimental evidence however shows that this behaviour is more complex than assumed in this model, thus opening up new avenues for research.

  10. Microbial synthesis of iron-based nanomaterials—A review

    Indian Academy of Sciences (India)

    Abhilash; K Revati; B D Pandey

    2011-04-01

    Nanoparticles are the materials having dimensions of the order of 100 nm or less. They exhibit a high surface/volume ratio leading to different properties far different from those of the bulk materials. The development of uniform nanoparticles has been intensively pursued because of their technological and fundamental scientific importance. A number of chemical methods are available and are extensively used, but these are often energy intensive and employ toxic chemicals. An alternative approach for the synthesis of uniform nanoparticles is the biological route that occurs at ambient temperature, pressure and at neutral pH. The main aim of this review is to enlist and compare various methods of synthesis of iron-based nanoparticles with emphasis on the biological method. Biologically induced and controlled mineralization mechanisms are the two modes through which the micro-organisms synthesize iron oxide nanoparticles. In biologically induced mineralization (BIM) mode, the environmental factors like pH, pO2, pCO2, redox potential, temperature etc govern the synthesis of iron oxide nanoparticles. In contrast, biologically controlled mineralization (BCM) process initiates the micro-organism itself to control the synthesis. BIM can be observed in the Fe(III) reducing bacterial species of Shewanella, Geobacter, Thermoanaerobacter, and sulphate reducing bacterial species of Archaeoglobus fulgidus, Desulfuromonas acetoxidans, whereas BCM mode can be observed in the magnetotactic bacteria (MTB) like Magnetospirillum magnetotacticum, M. gryphiswaldense and sulphate-reducing magnetic bacteria (Desulfovibrio magneticus). Magnetite crystals formed by Fe(III)-reducing bacteria are epicellular, poorly crystalline, irregular in shapes, having a size range of 10–50 nm super-paramagnetic particles, with a saturation magnetization value ranging from 75–77 emu/g and are not aligned in chains. Magnetite crystals produced by MTB have uniform species-specific morphologies and sizes

  11. Macrozoobenthos community structure of the Bohai Bay in spring time%春季渤海湾大型底栖动物群落结构特征研究

    Institute of Scientific and Technical Information of China (English)

    蔡文倩; 孟伟; 刘录三; 朱延忠; 周娟

    2013-01-01

    本文以2009年5月渤海湾近岸海域采集的大型底栖动物样品和环境资料为基础,分析其群落结构特征,并运用香浓-维纳多样性指数、AZTI海洋生物指数(AZTI's Marine Biotic Index,AMBI)和多元AZTI生物指数(Multivariate-AMBI,M-AMBI)对渤海湾底栖生态环境质量状况进行评价.结果表明,渤海湾底栖动物群落的物种数、栖息密度、生物量及多样性指数低值区皆集中在河口区、排污口区以及港口附近海域,群落结构比较脆弱,物种明显小型化、低质化.渤海湾受到干扰最严重的区域集中在黄骅港、蓟运河口、北塘排污口以及南、北排水河口区附近海域.盐度、水深等环境因子及围海造陆、污染物排放等人为干扰因素联合作用,直接或间接地影响渤海湾大型底栖动物群落.与历史资料相比,渤海湾底栖生物群落发生了较大变化,物种数、生物量和栖息密度急剧下降,河口、排污口区以及港口附近尤为明显;渤海湾环境质量状况可能较优于莱州湾、辽东湾.%Based on the macrozoobenthos and environmental materials collected in May 2009, the characteristics of macrozoobenthos community structure in the Bohai Bay were analyzed. The Shannon-Weiner Diversity index, AMBI and M-AMB1 were used to assess the ecological status of the Bohai Bay. Results showed that the species compositions of macrozoobenthos community were dominated by some short-lived taxa which smaller size indicated that the community structure of Bohai Bay was unhealthy and unstable to a certain degree. Lower values of species number, density, biomass and diversity index were concentrated in the main estuaries, outlets and the adjacent areas of harbors. The most severely disturbed areas of Bohai Bay were in accordance with that of the community structure parameters, mainly concentrated in the Huanghua Harbor, Jiyun River estuary, Beitang Outlets, Nanpaishui River estuary and Beipaishui River estuary

  12. Probabilistic Assessment of Hypobaric Decompression Sickness Treatment Success

    Science.gov (United States)

    Conkin, Johnny; Abercromby, Andrew F. J.; Dervay, Joseph P.; Feiveson, Alan H.; Gernhardt, Michael L.; Norcross, Jason R.; Ploutz-Snyder, Robert; Wessel, James H., III

    2014-01-01

    The Hypobaric Decompression Sickness (DCS) Treatment Model links a decrease in computed bubble volume from increased pressure (DeltaP), increased oxygen (O2) partial pressure, and passage of time during treatment to the probability of symptom resolution [P(symptom resolution)]. The decrease in offending volume is realized in 2 stages: a) during compression via Boyle's Law and b) during subsequent dissolution of the gas phase via the O2 window. We established an empirical model for the P(symptom resolution) while accounting for multiple symptoms within subjects. The data consisted of 154 cases of hypobaric DCS symptoms along with ancillary information from tests on 56 men and 18 women. Our best estimated model is P(symptom resolution) = 1 / (1+exp(-(ln(Delta P) - 1.510 + 0.795×AMB - 0.00308×Ts) / 0.478)), where (DeltaP) is pressure difference (psid), AMB = 1 if ambulation took place during part of the altitude exposure, otherwise AMB = 0; and where Ts is the elapsed time in mins from start of the altitude exposure to recognition of a DCS symptom. To apply this model in future scenarios, values of DeltaP as inputs to the model would be calculated from the Tissue Bubble Dynamics Model based on the effective treatment pressure: (DeltaP) = P2 - P1 | = P1×V1/V2 - P1, where V1 is the computed volume of a spherical bubble in a unit volume of tissue at low pressure P1 and V2 is computed volume after a change to a higher pressure P2. If 100% ground level O2 (GLO) was breathed in place of air, then V2 continues to decrease through time at P2 at a faster rate. This calculated value of (DeltaP then represents the effective treatment pressure at any point in time. Simulation of a "pain-only" symptom at 203 min into an ambulatory extravehicular activity (EVA) at 4.3 psia on Mars resulted in a P(symptom resolution) of 0.49 (0.36 to 0.62 95% confidence intervals) on immediate return to 8.2 psia in the Multi-Mission Space Exploration Vehicle. The P(symptom resolution) increased