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Sample records for mat-forming filamentous cyanobacterium

  1. Seeking sunlight: rapid phototactic motility of filamentous mat-forming cyanobacteria optimize photosynthesis and enhance carbon burial in Lake Huron’s submerged sinkholes

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    Bopaiah A Biddanda

    2015-09-01

    Full Text Available We studied the motility of filamentous mat-forming cyanobacteria consisting primarily of Oscillatoria-like cells growing under low-light, low-oxygen and high-sulfur conditions in Lake Huron’s submerged sinkholes using in situ observations, in vitro measurements and time-lapse microscopy. Gliding movement of the cyanobacterial trichomes (100-10,000 µm long filaments, composed of cells ~10 µm wide and ~3 µm tall revealed individual as well as group-coordinated motility. When placed in a petri dish and dispersed in ground water from the sinkhole, filaments re-aggregated into defined colonies within minutes, then dispersed again. Speed of individual filaments increased with temperature from ~50 µm minute-1 or ~15 body lengths minute-1 at 10°C to ~215 µm minute-1 or ~70 body lengths minute-1 at 35°C – rates that are rapid relative to non-flagellated/ciliated microbes. Filaments exhibited precise and coordinated positive phototaxis towards pinpoints of light and congregated under the light of foil cutouts. Such light-responsive clusters showed an increase in photosynthetic yield – suggesting phototactic motility aids in light acquisition as well as photosynthesis. Once light source was removed, filaments slowly spread out evenly and re-aggregated, demonstrating coordinated movement through inter-filament communication regardless of light. Pebbles and pieces of broken shells placed upon intact mat were quickly covered by vertically motile filaments within hours and became fully buried in the anoxic sediments over 3-4 diurnal cycles – likely facilitating the preservation of falling debris. Coordinated horizontal and vertical filament motility optimize mat cohesion and dynamics, photosynthetic efficiency and sedimentary carbon burial in modern-day sinkhole habitats that resemble the shallow seas in Earth’s early history. Analogous cyanobacterial motility may have played a key role in the oxygenation of the planet by optimizing

  2. Seeking sunlight: rapid phototactic motility of filamentous mat-forming cyanobacteria optimize photosynthesis and enhance carbon burial in Lake Huron's submerged sinkholes.

    Science.gov (United States)

    Biddanda, Bopaiah A; McMillan, Adam C; Long, Stephen A; Snider, Michael J; Weinke, Anthony D

    2015-01-01

    We studied the motility of filamentous mat-forming cyanobacteria consisting primarily of Oscillatoria-like cells growing under low-light, low-oxygen, and high-sulfur conditions in Lake Huron's submerged sinkholes using in situ observations, in vitro measurements and time-lapse microscopy. Gliding movement of the cyanobacterial trichomes (100-10,000 μm long filaments, composed of cells ∼10 μm wide and ∼3 μm tall) revealed individual as well as group-coordinated motility. When placed in a petri dish and dispersed in ground water from the sinkhole, filaments re-aggregated into defined colonies within minutes, then dispersed again. Speed of individual filaments increased with temperature from ∼50 μm min(-1) or ∼15 body lengths min(-1) at 10°C to ∼215 μm min(-1) or ∼70 body lengths min(-1) at 35°C - rates that are rapid relative to non-flagellated/ciliated microbes. Filaments exhibited precise and coordinated positive phototaxis toward pinpoints of light and congregated under the light of foil cutouts. Such light-responsive clusters showed an increase in photosynthetic yield - suggesting phototactic motility aids in light acquisition as well as photosynthesis. Once light source was removed, filaments slowly spread out evenly and re-aggregated, demonstrating coordinated movement through inter-filament communication regardless of light. Pebbles and pieces of broken shells placed upon intact mat were quickly covered by vertically motile filaments within hours and became fully buried in the anoxic sediments over 3-4 diurnal cycles - likely facilitating the preservation of falling debris. Coordinated horizontal and vertical filament motility optimize mat cohesion and dynamics, photosynthetic efficiency and sedimentary carbon burial in modern-day sinkhole habitats that resemble the shallow seas in Earth's early history. Analogous cyanobacterial motility may have played a key role in the oxygenation of the planet by optimizing photosynthesis while favoring

  3. Seeking sunlight: rapid phototactic motility of filamentous mat-forming cyanobacteria optimize photosynthesis and enhance carbon burial in Lake Huron’s submerged sinkholes

    Science.gov (United States)

    Biddanda, Bopaiah A.; McMillan, Adam C.; Long, Stephen A.; Snider, Michael J.; Weinke, Anthony D.

    2015-01-01

    We studied the motility of filamentous mat-forming cyanobacteria consisting primarily of Oscillatoria-like cells growing under low-light, low-oxygen, and high-sulfur conditions in Lake Huron’s submerged sinkholes using in situ observations, in vitro measurements and time-lapse microscopy. Gliding movement of the cyanobacterial trichomes (100–10,000 μm long filaments, composed of cells ∼10 μm wide and ∼3 μm tall) revealed individual as well as group-coordinated motility. When placed in a petri dish and dispersed in ground water from the sinkhole, filaments re-aggregated into defined colonies within minutes, then dispersed again. Speed of individual filaments increased with temperature from ∼50 μm min-1 or ∼15 body lengths min-1 at 10°C to ∼215 μm min-1 or ∼70 body lengths min-1 at 35°C – rates that are rapid relative to non-flagellated/ciliated microbes. Filaments exhibited precise and coordinated positive phototaxis toward pinpoints of light and congregated under the light of foil cutouts. Such light-responsive clusters showed an increase in photosynthetic yield – suggesting phototactic motility aids in light acquisition as well as photosynthesis. Once light source was removed, filaments slowly spread out evenly and re-aggregated, demonstrating coordinated movement through inter-filament communication regardless of light. Pebbles and pieces of broken shells placed upon intact mat were quickly covered by vertically motile filaments within hours and became fully buried in the anoxic sediments over 3–4 diurnal cycles – likely facilitating the preservation of falling debris. Coordinated horizontal and vertical filament motility optimize mat cohesion and dynamics, photosynthetic efficiency and sedimentary carbon burial in modern-day sinkhole habitats that resemble the shallow seas in Earth’s early history. Analogous cyanobacterial motility may have played a key role in the oxygenation of the planet by optimizing photosynthesis while

  4. Evidence for paralytic shellfish poisons in the freshwater cyanobacterium Lyngbya wollei (Farlow ex Gomont) comb. nov.

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    Carmichael, W W; Evans, W R; Yin, Q Q; Bell, P; Moczydlowski, E

    1997-01-01

    Lyngbya wollei (Farlow ex Gomont) comb. nov., a perennial mat-forming filamentous cyanobacterium prevalent in lakes and reservoirs of the southeastern United States, was found to produce a potent, acutely lethal neurotoxin when tested in the mouse bioassay. Signs of poisoning were similar to those of paralytic shellfish poisoning. As part of the Tennessee Valley Authority master plan for Guntersville Reservoir, the mat-forming filamentous cyanobacterium L. wollei, a species that had recently ...

  5. Antagonistic interactions between filamentous heterotrophs and the cyanobacterium Nostoc muscorum

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    Wolf Sarah

    2011-09-01

    Full Text Available Abstract Background Little is known about interactions between filamentous heterotrophs and filamentous cyanobacteria. Here, interactions between the filamentous heterotrophic bacteria Fibrella aestuarina (strain BUZ 2 and Fibrisoma limi (BUZ 3 with an axenic strain of the autotrophic filamentous cyanobacterium Nostoc muscorum (SAG 25.82 were studied in mixed cultures under nutrient rich (carbon source present in medium and poor (carbon source absent in medium conditions. Findings F. aestuarina BUZ 2 significantly reduced the cyanobacterial population whereas F. limi BUZ 3 did not. Physical contact between heterotrophs and autotroph was observed and the cyanobacterial cells showed some level of damage and lysis. Therefore, either contact lysis or entrapment with production of extracellular compounds in close vicinity of host cells could be considered as potential modes of action. The supernatants from pure heterotrophic cultures did not have an effect on Nostoc cultures. However, supernatant from mixed cultures of BUZ 2 and Nostoc had a negative effect on cyanobacterial growth, indicating that the lytic compounds were only produced in the presence of Nostoc. The growth and survival of tested heterotrophs was enhanced by the presence of Nostoc or its metabolites, suggesting that the heterotrophs could utilize the autotrophs and its products as a nutrient source. However, the autotroph could withstand and out-compete the heterotrophs under nutrient poor conditions. Conclusions Our results suggest that the nutrients in cultivation media, which boost or reduce the number of heterotrophs, were the important factor influencing the outcome of the interplay between filamentous heterotrophs and autotrophs. For better understanding of these interactions, additional research is needed. In particular, it is necessary to elucidate the mode of action for lysis by heterotrophs, and the possible defense mechanisms of the autotrophs.

  6. Detection of Bioactive Exometabolites Produced by the Filamentous Marine Cyanobacterium Geitlerinema sp.

    OpenAIRE

    Caicedo, Nelson H.; Kumirska, Jolanta; Neumann, Jennifer; Stolte, Stefan; Thöming, Jorg

    2011-01-01

    Marine cyanobacteria are noted for their ability to excrete metabolites with biotic properties. This paper focuses on such exometabolites obtained from the culture of the marine filamentous cyanobacterium Geitlerinema sp. strain, their purification and subsequent analyses. By this means the recoveries of the active compounds, a prerequisite for properly determining their concentration, are quantified here for the first time. We demonstrate a new procedure using Amberlite XAD-1180 resin in com...

  7. Detection of bioactive exometabolites produced by the filamentous marine cyanobacterium Geitlerinema sp.

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    Caicedo, Nelson H; Kumirska, Jolanta; Neumann, Jennifer; Stolte, Stefan; Thöming, Jorg

    2012-08-01

    Marine cyanobacteria are noted for their ability to excrete metabolites with biotic properties. This paper focuses on such exometabolites obtained from the culture of the marine filamentous cyanobacterium Geitlerinema sp. strain, their purification and subsequent analyses. By this means the recoveries of the active compounds, a prerequisite for properly determining their concentration, are quantified here for the first time. We demonstrate a new procedure using Amberlite XAD-1180 resin in combination with the eluent isopropanol for extraction of the culture media and gas chromatography as simplified chemical analysis. This procedure reduced necessary bacteria cultivation time (from 150 to 21 days) at low volumes of culture media (300 mL) required for identification of two selected bioactive compounds: 4,4'-dihydroxybiphenyl and harmane.

  8. Sterol Compositions of the Filamentous Nitrogen-Fixing Terrestrial Cyanobacterium Scytonema sp

    Czech Academy of Sciences Publication Activity Database

    Řezanka, Tomáš; Dembitsky, V. M.; Go, J. V.; Dor, I.; Prell, Aleš; Hanuš, L.

    2003-01-01

    Roč. 48, č. 3 (2003), s. 357-360 ISSN 0015-5632 Institutional research plan: CEZ:AV0Z5020903 Keywords : nitrogen-fixing * cyanobacterium * scytonema Subject RIV: EE - Microbiology, Virology Impact factor: 0.857, year: 2003

  9. The effects of the exopolysaccharide and growth rate on the morphogenesis of the terrestrial filamentous cyanobacterium Nostoc flagelliforme

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    Lijuan Cui

    2017-09-01

    Full Text Available The terrestrial cyanobacterium Nostoc flagelliforme, which contributes to carbon and nitrogen supplies in arid and semi-arid regions, adopts a filamentous colony form. Owing to its herbal and dietary values, this species has been overexploited. Largely due to the lack of understanding on its morphogenesis, artificial cultivation has not been achieved. Additionally, it may serve as a useful model for recognizing the morphological adaptation of colonial cyanobacteria in terrestrial niches. However, it shows very slow growth in native habitats and is easily disintegrated under laboratory conditions. Thus, a novel experimental system is necessary to explore its morphogenetic mechanism. Liquid-cultured N. flagelliforme has been well developed for exopolysaccharide (EPS production, in which microscopic colonies (micro-colonies are generally formed. In this study, we sought to gain some insight into the morphogenesis of N. flagelliforme by examining the effects of two external factors, the EPS and environmental stress-related growth rate, on the morphological shaping of micro-colonies. Our findings indicate that the EPS matrix could act as a basal barrier, leading to the bending of trichomes during their elongation, while very slow growth is conducive to their straight elongation. These findings will guide future cultivation and application of this cyanobacterium for ecological improvement.

  10. Dynamic localization of HmpF regulates type IV pilus activity and directional motility in the filamentous cyanobacterium Nostoc punctiforme.

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    Cho, Ye Won; Gonzales, Alfonso; Harwood, Thomas V; Huynh, Jessica; Hwang, Yeji; Park, Jun Sang; Trieu, Anthony Q; Italia, Parth; Pallipuram, Vivek K; Risser, Douglas D

    2017-10-01

    Many cyanobacteria exhibit surface motility powered by type 4 pili (T4P). In the model filamentous cyanobacterium Nostoc punctiforme, the T4P systems are arrayed in static, bipolar rings in each cell. The chemotaxis-like Hmp system is essential for motility and the coordinated polar accumulation of PilA on cells in motile filaments, while the Ptx system controls positive phototaxis. Using transposon mutagenesis, a gene, designated hmpF, was identified as involved in motility. Synteny among filamentous cyanobacteria and the similar expression patterns for hmpF and hmpD imply that HmpF is part of the Hmp system. Deletion of hmpF produced a phenotype distinct from other hmp genes, but indistinguishable from pilB or pilQ. Both an HmpF-GFPuv fusion protein, and PilA, as assessed by in situ immunofluorescence, displayed coordinated, unipolar localization at the leading pole of each cell. Reversals were modulated by changes in light intensity and preceded by the migration of HmpF-GFPuv to the lagging cell poles. These results are consistent with a model where direct interaction between HmpF and the T4P system activates pilus extension, the Hmp system facilitates coordinated polarity of HmpF to establish motility, and the Ptx system modulates HmpF localization to initiate reversals in response to changes in light intensity. © 2017 John Wiley & Sons Ltd.

  11. The non-metabolizable sucrose analog sucralose is a potent inhibitor of hormogonium differentiation in the filamentous cyanobacterium Nostoc punctiforme.

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    Splitt, Samantha D; Risser, Douglas D

    2016-03-01

    Nostoc punctiforme is a filamentous cyanobacterium which forms nitrogen-fixing symbioses with several different plants and fungi. Establishment of these symbioses requires the formation of motile hormogonium filaments. Once infected, the plant partner is thought to supply a hormogonium-repressing factor (HRF) to maintain the cyanobacteria in a vegetative, nitrogen-fixing state. Evidence implies that sucrose may serve as a HRF. Here, we tested the effects of sucralose, a non-metabolizable sucrose analog, on hormogonium differentiation. Sucralose inhibited hormogonium differentiation at a concentration approximately one-tenth that of sucrose. This result implies that: (1) sucrose, not a sucrose catabolite, is perceived by the cell and (2) inhibition is not due to a more general osmolarity-dependent effect. Additionally, both sucrose and sucralose induced the accrual of a polysaccharide sheath which bound specifically to the lectin ConA, indicating the presence of α-D-mannose and/or α-D-glucose. A ConA-specific polysaccharide was also found to be expressed in N. punctiforme colonies from tissue sections of the symbiotically grown hornwort Anthoceros punctatus. These findings imply that plant-derived sucrose or sucrose analogs may have multiple effects on N. punctiforme, including both repression of hormogonia and the induction of a polysaccharide sheath that may be essential to establish and maintain the symbiotic state.

  12. Aspects of the ecology of mat-forming lichens

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    P. D. Crittenden

    2000-03-01

    Full Text Available Lichen species in the genera Cladonia (subgenus Cladina, Cetraria, Stereocaulon and Alectoria are important vegetation components on well-drained terrain and on elevated micro-sites in peatlands in boreal-Arctic regions. These lichens often form closed mats, the component thalli in which grow vertically upwards at the apices and die off in the older basal regions; they are therefore only loosely attached to the underlying soil. This growth habit is relatively unusual in lichens being found in <0.5% of known species. It might facilitate internal nutrienr recycling and higher growth rates and, together with the production of allelochemicals, it might underlie the considerable ecological success of mat-forming lichens; experiments to critically assess the importance of these processes are required. Mat-forming lichens can constitute in excess of 60% of the winter food intake of caribou and reindeer. Accordingly there is a pressing need for data on lichen growth rates, measured as mass increment, in order to help determine the carrying capacity of winter ranges for rhese herbivores and to better predict recovery rates following grazing. Trampling during the snow-free season fragments lichen thalli; mat-forming lichens regenerate very successfully from thallus fragments provided trampling does nor re-occur. Frequent recurrence of trampling creates disturbed habitats from which lichens will rapidly become eliminated consistent with J.P. Grime's CSR strategy theory. Such damage to lichen ground cover has occurred where reindeer or caribou are unable to migrate away from their winter range such as on small islands or where political boundaries have been fenced; it can also occur on summer range that contains a significant lichen component and on winter range where numbers of migrarory animals become excessive. Species of Stereocaulon, and other genera that contain cyanobacteria (most notably Peltigera and Nephroma, are among the principal agents of

  13. Draft Genome Sequence of Leptolyngbya sp. KIOST-1, a Filamentous Cyanobacterium with Biotechnological Potential for Alimentary Purposes.

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    Kim, Ji Hyung; Kang, Do-Hyung

    2016-09-15

    Here, we report the draft genome of cyanobacterium Leptolyngbya sp. KIOST-1 isolated from a microalgal culture pond in South Korea. The genome consists of 13 contigs containing 6,320,172 bp, and a total of 5,327 coding sequences were predicted. This genomic information will allow further exploitation of its biotechnological potential for alimentary purposes. Copyright © 2016 Kim and Kang.

  14. Effects of the filamentous cyanobacterium Nodularia on fitness and feeding behavior of young-of-the-year (YOY) Eurasian perch (Perca fluviatilis).

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    Persson, Karl-Johan; Stenroth, Patrik; Legrand, Catherine

    2011-06-01

    This study reveals that both cyanobacterial toxicity and turbidity have the potential to reduce the growth and energy storage of young-of-the-year (YOY) perch and thereby influence survival rates. During the 1990's a reduction in recruitment of YOY perch (Perca fluviatilis) occurred along the Swedish East coast. Concurrently, large blooms of filamentous cyanobacteria have increased in the Baltic Proper and in coastal waters. This study examined whether extended exposure to toxic and non-toxic filamentous cyanobacterium Nodularia affect YOY perch growth and feeding behavior under simulated bloom conditions (30 days at 50 μg Chl a L(-1)). Specific growth rate (SGR), the somatic condition index (SCI) and the lipid content of YOY perch (10-12 weeks old) were significantly lower in perch exposed to Nodularia compared to fed controls (no Nodularia). YOY perch exposed to non-toxic Nodularia displayed a higher attack rate than perch living in Nodularia free controls in 2 out of 3 trials. Reductions in growth and energy storage, mediated by cyanobacteria, increase the risk of starvation and predation and could locally influence recruitment of YOY perch. Copyright © 2011 Elsevier Ltd. All rights reserved.

  15. Optimization and effects of different culture conditions on growth of Halomicronema hongdechloris – a filamentous cyanobacterium containing chlorophyll f

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    Yaqiong eLi

    2014-02-01

    Full Text Available A chlorophyll f containing cyanobacterium, Halomicronema hongdechloris (H. hongdechloris was isolated from a stromatolite cyanobacterial community. However, the extremely slower growth rate of H. hongdechloris culture became a critical factor, hindering the research on this newly isolated cyanobacterium and the investigation of chlorophyll f-photosynthesis. Therefore, optimizing H. hongdechloris culture conditions has become an essential requirement for future research. This work investigated the effects of various culture conditions, essential nutrients and light environments to determine the optimal growth conditions for H. hongdechloris and the biosynthetic rate of chlorophyll f. Based on the total chlorophyll concentration, an optimal growth rate of 0.22 ± 0.02 day-1 (doubling time: 3.1 ± 0.3 days was observed when cells were grown under continuous illumination with far-red light with an intensity of 20 µE at 32°C in modified K+ES seawater (pH 8.0 with additional supplements of 11.75 mM NaNO3 and 0.15 mM K2HPO4. High performance liquid chromatography on H. hongdechloris pigments confirmed that chlorophyll a is the major chlorophyll and chlorophyll f constitutes approximately 10% of the total chlorophyll from cells grown under far-red light. Fluorescence confocal image analysis demonstrated changes of photosynthetic membranes and the distribution of photopigments in response to different light conditions. The total photosynthetic oxygen evolution yield per cell showed no changes under different light conditions, which confirms the involvement of chlorophyll f in oxygenic photosynthesis. The implications of the presence of chlorophyll f in H. hongdechloris and its relationship to light environment are discussed.

  16. Analysis of the early heterocyst Cys-proteome in the multicellular cyanobacterium Nostoc punctiforme reveals novel insights into the division of labor within diazotrophic filaments.

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    Sandh, Gustaf; Ramström, Margareta; Stensjö, Karin

    2014-12-04

    In the filamentous cyanobacterium Nostoc punctiforme ATCC 29133, removal of combined nitrogen induces the differentiation of heterocysts, a cell-type specialized in N2 fixation. The differentiation involves genomic, structural and metabolic adaptations. In cyanobacteria, changes in the availability of carbon and nitrogen have also been linked to redox regulated posttranslational modifications of protein bound thiol groups. We have here employed a thiol targeting strategy to relatively quantify the putative redox proteome in heterocysts as compared to N2-fixing filaments, 24 hours after combined nitrogen depletion. The aim of the study was to expand the coverage of the cell-type specific proteome and metabolic landscape of heterocysts. Here we report the first cell-type specific proteome of newly formed heterocysts, compared to N2-fixing filaments, using the cysteine-specific selective ICAT methodology. The data set defined a good quantitative accuracy of the ICAT reagent in complex protein samples. The relative abundance levels of 511 proteins were determined and 74% showed a cell-type specific differential abundance. The majority of the identified proteins have not previously been quantified at the cell-type specific level. We have in addition analyzed the cell-type specific differential abundance of a large section of proteins quantified in both newly formed and steady-state diazotrophic cultures in N. punctiforme. The results describe a wide distribution of members of the putative redox regulated Cys-proteome in the central metabolism of both vegetative cells and heterocysts of N. punctiforme. The data set broadens our understanding of heterocysts and describes novel proteins involved in heterocyst physiology, including signaling and regulatory proteins as well as a large number of proteins with unknown function. Significant differences in cell-type specific abundance levels were present in the cell-type specific proteomes of newly formed diazotrophic filaments

  17. Single-cell confocal spectrometry of a filamentous cyanobacterium Nostoc at room and cryogenic temperature. Diversity and differentiation of pigment systems in 311 cells.

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    Sugiura, Kana; Itoh, Shigeru

    2012-08-01

    The fluorescence spectrum at 298 and 40 K and the absorption spectrum at 298 K of each cell of the filamentous cyanobacterium Nostoc sp. was measured by single-cell confocal laser spectroscopy to study the differentiation of cell pigments. The fluorescence spectra of vegetative (veg) and heterocyst (het) cells of Nostoc formed separate groups with low and high PSII to PSI ratios, respectively. The fluorescence spectra of het cells at 40 K still contained typical PSII bands. The PSII/PSI ratio estimated for the veg cells varied between 0.4 and 1.2, while that of het cells varied between 0 and 0.22 even in the same culture. The PSII/PSI ratios of veg cells resembled each other more closely in the same filament. 'pro-het' cells, which started to differentiate into het cells, were identified from the small but specific difference in the PSII/PSI ratio. The allophycocyanin (APC)/PSII ratio was almost constant in both veg and het cells, indicating their tight couplings. Phycocyanin (PC) showed higher fluorescence in most het cells, suggesting the uncoupling from PSII. Veg cells seem to vary their PSI contents to give different PSII/PSI ratios even in the same culture, and to suppress the synthesis of PSII, APC and PC to differentiate into het cells. APC and PC are gradually liberated from membranes in het cells with the uncoupling from PSII. Single-cell spectrometry will be useful to study the differentiation of intrinsic pigments of cells and chloroplasts, and to select microbes from natural environments.

  18. Soft x-ray imaging of intracellular granules of filamentous cyanobacterium generating musty smell in Lake Biwa

    International Nuclear Information System (INIS)

    Takemoto, K; Mizuta, G; Namba, H; Yamamoto, A; Kihara, H; Yoshimura, M; Ichise, S

    2013-01-01

    A planktonic blue-green algae, which are currently identified as Phormidium tenue, was observed by a soft x-ray microscopy (XM) for comparing a musty smell generating green strain (PTG) and a non-smell brown strain (PTB). By XM, cells were clearly imaged, and several intracellular granules which could not be observed under a light microscope were visualized. The diameter of granules was about 0.5–1 μm, and one or a few granules were seen in a cell. XM analyses showed that width of cells and sizes of intracellular granules were quite different between PTG and PTB strains. To study the granules observed by XM, transmission in more detail, transmission electron microscopy (TEM) and indirect fluorescent-antibody technique (IFA) were applied. By TEM, carboxysomes, thylakoids and polyphosphate granules were observed. IFA showed the presence of carboxysomes. Results lead to the conclusion that intracellular granules observed under XM are carboxysomes or polyphosphate granules. These results demonstrate that soft XM is effective for analyzing fine structures of small organisms such as cyanobacterium, and for discriminating the strains which generates musty smells from others

  19. Sulfate-driven elemental sparing is regulated at the transcriptional and posttranscriptional levels in a filamentous cyanobacterium.

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    Gutu, Andrian; Alvey, Richard M; Bashour, Sami; Zingg, Daniel; Kehoe, David M

    2011-03-01

    Sulfur is an essential nutrient that can exist at growth-limiting concentrations in freshwater environments. The freshwater cyanobacterium Fremyella diplosiphon (also known as Tolypothrix sp. PCC 7601) is capable of remodeling the composition of its light-harvesting antennae, or phycobilisomes, in response to changes in the sulfur levels in its environment. Depletion of sulfur causes these cells to cease the accumulation of two forms of a major phycobilisome protein called phycocyanin and initiate the production of a third form of phycocyanin, which possesses a minimal number of sulfur-containing amino acids. Since phycobilisomes make up approximately 50% of the total protein in these cells, this elemental sparing response has the potential to significantly influence the fitness of this species under low-sulfur conditions. This response is specific for sulfate and occurs over the physiological range of sulfate concentrations likely to be encountered by this organism in its natural environment. F. diplosiphon has two separate sulfur deprivation responses, with low sulfate levels activating the phycobilisome remodeling response and low sulfur levels activating the chlorosis or bleaching response. The phycobilisome remodeling response results from changes in RNA abundance that are regulated at both the transcriptional and posttranscriptional levels. The potential of this response, and the more general bleaching response of cyanobacteria, to provide sulfur-containing amino acids during periods of sulfur deprivation is examined.

  20. Viruses Infecting a Freshwater Filamentous Cyanobacterium (Nostoc sp.) Encode a Functional CRISPR Array and a Proteobacterial DNA Polymerase B.

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    Chénard, Caroline; Wirth, Jennifer F; Suttle, Curtis A

    2016-06-14

    Here we present the first genomic characterization of viruses infecting Nostoc, a genus of ecologically important cyanobacteria that are widespread in freshwater. Cyanophages A-1 and N-1 were isolated in the 1970s and infect Nostoc sp. strain PCC 7210 but remained genomically uncharacterized. Their 68,304- and 64,960-bp genomes are strikingly different from those of other sequenced cyanophages. Many putative genes that code for proteins with known functions are similar to those found in filamentous cyanobacteria, showing a long evolutionary history in their host. Cyanophage N-1 encodes a CRISPR array that is transcribed during infection and is similar to the DR5 family of CRISPRs commonly found in cyanobacteria. The presence of a host-related CRISPR array in a cyanophage suggests that the phage can transfer the CRISPR among related cyanobacteria and thereby provide resistance to infection with competing phages. Both viruses also encode a distinct DNA polymerase B that is closely related to those found in plasmids of Cyanothece sp. strain PCC 7424, Nostoc sp. strain PCC 7120, and Anabaena variabilis ATCC 29413. These polymerases form a distinct evolutionary group that is more closely related to DNA polymerases of proteobacteria than to those of other viruses. This suggests that the polymerase was acquired from a proteobacterium by an ancestral virus and transferred to the cyanobacterial plasmid. Many other open reading frames are similar to a prophage-like element in the genome of Nostoc sp. strain PCC 7524. The Nostoc cyanophages reveal a history of gene transfers between filamentous cyanobacteria and their viruses that have helped to forge the evolutionary trajectory of this previously unrecognized group of phages. Filamentous cyanobacteria belonging to the genus Nostoc are widespread and ecologically important in freshwater, yet little is known about the genomic content of their viruses. Here we report the first genomic analysis of cyanophages infecting

  1. A Putative O-Linked β-N-Acetylglucosamine Transferase Is Essential for Hormogonium Development and Motility in the Filamentous Cyanobacterium Nostoc punctiforme.

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    Khayatan, Behzad; Bains, Divleen K; Cheng, Monica H; Cho, Ye Won; Huynh, Jessica; Kim, Rachelle; Omoruyi, Osagie H; Pantoja, Adriana P; Park, Jun Sang; Peng, Julia K; Splitt, Samantha D; Tian, Mason Y; Risser, Douglas D

    2017-05-01

    Most species of filamentous cyanobacteria are capable of gliding motility, likely via a conserved type IV pilus-like system that may also secrete a motility-associated polysaccharide. In a subset of these organisms, motility is achieved only after the transient differentiation of hormogonia, which are specialized filaments that enter a nongrowth state dedicated to motility. Despite the fundamental importance of hormogonia to the life cycles of many filamentous cyanobacteria, the molecular regulation of hormogonium development is largely undefined. To systematically identify genes essential for hormogonium development and motility in the model heterocyst-forming filamentous cyanobacterium Nostoc punctiforme , a forward genetic screen was employed. The first gene identified using this screen, designated ogtA , encodes a putative O-linked β- N -acetylglucosamine transferase (OGT). The deletion of ogtA abolished motility, while ectopic expression of ogtA induced hormogonium development even under hormogonium-repressing conditions. Transcription of ogtA is rapidly upregulated (1 h) following hormogonium induction, and an OgtA-GFPuv fusion protein localized to the cytoplasm. In developing hormogonia, accumulation of PilA but not HmpD is dependent on ogtA Reverse transcription-quantitative PCR (RT-qPCR) analysis indicated equivalent levels of pilA transcript in the wild-type and Δ ogtA mutant strains, while a reporter construct consisting of the intergenic region in the 5' direction of pilA fused to gfp produced lower levels of fluorescence in the Δ ogtA mutant strain than in the wild type. The production of hormogonium polysaccharide in the Δ ogtA mutant strain is reduced compared to that in the wild type but comparable to that in a pilA deletion strain. Collectively, these results imply that O -GlcNAc protein modification regulates the accumulation of PilA via a posttranscriptional mechanism in developing hormogonia. IMPORTANCE Filamentous cyanobacteria are among

  2. Viruses Infecting a Freshwater Filamentous Cyanobacterium (Nostoc sp. Encode a Functional CRISPR Array and a Proteobacterial DNA Polymerase B

    Directory of Open Access Journals (Sweden)

    Caroline Chénard

    2016-06-01

    Full Text Available Here we present the first genomic characterization of viruses infecting Nostoc, a genus of ecologically important cyanobacteria that are widespread in freshwater. Cyanophages A-1 and N-1 were isolated in the 1970s and infect Nostoc sp. strain PCC 7210 but remained genomically uncharacterized. Their 68,304- and 64,960-bp genomes are strikingly different from those of other sequenced cyanophages. Many putative genes that code for proteins with known functions are similar to those found in filamentous cyanobacteria, showing a long evolutionary history in their host. Cyanophage N-1 encodes a CRISPR array that is transcribed during infection and is similar to the DR5 family of CRISPRs commonly found in cyanobacteria. The presence of a host-related CRISPR array in a cyanophage suggests that the phage can transfer the CRISPR among related cyanobacteria and thereby provide resistance to infection with competing phages. Both viruses also encode a distinct DNA polymerase B that is closely related to those found in plasmids of Cyanothece sp. strain PCC 7424, Nostoc sp. strain PCC 7120, and Anabaena variabilis ATCC 29413. These polymerases form a distinct evolutionary group that is more closely related to DNA polymerases of proteobacteria than to those of other viruses. This suggests that the polymerase was acquired from a proteobacterium by an ancestral virus and transferred to the cyanobacterial plasmid. Many other open reading frames are similar to a prophage-like element in the genome of Nostoc sp. strain PCC 7524. The Nostoc cyanophages reveal a history of gene transfers between filamentous cyanobacteria and their viruses that have helped to forge the evolutionary trajectory of this previously unrecognized group of phages.

  3. The biomechanical role of overall-shape transformation in a primitive multicellular organism: A case study of dimorphism in the filamentous cyanobacterium Arthrospira platensis.

    Science.gov (United States)

    Chaiyasitdhi, Atitheb; Miphonpanyatawichok, Wirat; Riehle, Mathis Oliver; Phatthanakun, Rungrueang; Surareungchai, Werasak; Kundhikanjana, Worasom; Kuntanawat, Panwong

    2018-01-01

    Morphological transformations in primitive organisms have long been observed; however, its biomechanical roles are largely unexplored. In this study, we investigate the structural advantages of dimorphism in Arthrospira platensis, a filamentous multicellular cyanobacterium. We report that helical trichomes, the default shape, have a higher persistence length (Lp), indicating a higher resistance to bending or a large value of flexural rigidity (kf), the product of the local cell stiffness (E) and the moment of inertia of the trichomes' cross-section (I). Through Atomic Force Microscopy (AFM), we determined that the E of straight and helical trichomes were the same. In contrast, our computational model shows that I is greatly dependent on helical radii, implying that trichome morphology is the major contributor to kf variation. According to our estimation, increasing the helical radii alone can increase kf by 2 orders of magnitude. We also observe that straight trichomes have improved gliding ability, due to its structure and lower kf. Our study shows that dimorphism provides mechanical adjustability to the organism and may allow it to thrive in different environmental conditions. The higher kf provides helical trichomes a better nutrient uptake through advection in aquatic environments. On the other hand, the lower kf improves the gliding ability of straight trichomes in aquatic environments, enabling it to chemotactically relocate to more favorable territories when it encounters certain environmental stresses. When more optimal conditions are encountered, straight trichomes can revert to their original helical form. Our study is one of the first to highlight the biomechanical role of an overall-shape transformation in cyanobacteria.

  4. 16S rRNA gene-based molecular analysis of mat-forming and accompanying bacteria covering organically-enriched marine sediments underlying a salmon farm in Southern Chile (Calbuco Island)

    OpenAIRE

    Aranda, Carlos; Paredes, Javier; Valenzuela, Cristian; Lam, Phyllis; Guillou, Laure

    2010-01-01

    The mat forming bacteria covering organic matter-enriched and anoxic marine sediments underlying a salmon farm in Southern Chile, were examined using 16S rRNA gene phylogenies. This mat was absent in the sea bed outside the direct influence of the farm (360 m outside fish cages). Based on nearly complete 16S rRNA gene sequences (-1500 bp), mat-forming filamentous cells were settled as the sulphur-oxidizing and putatively dissimilative nitrate-reducing Beggiatoa spp., being closely related (up...

  5. Distinctive fungal and bacterial communities are associated with mats formed by ectomycorrhizal fungi

    Science.gov (United States)

    Laurel A. Kluber; Jane E. Smith; David D. Myrold

    2011-01-01

    The distinct rhizomorphic mats formed by ectomycorrhizal Piloderma fungi are common features of the organic soil horizons of coniferous forests of the Pacific Northwest. These mats have been found to cover 25-40% of the forest floor in some Douglas-fir stands, and are associated with physical and biochemical properties that distinguish them from...

  6. Evidence for paralytic shellfish poisons in the freshwater cyanobacterium Lyngbya wollei (Farlow ex Gomont) comb. nov.

    Science.gov (United States)

    Carmichael, W W; Evans, W R; Yin, Q Q; Bell, P; Moczydlowski, E

    1997-08-01

    Lyngbya wollei (Farlow ex Gomont) comb. nov., a perennial mat-forming filamentous cyanobacterium prevalent in lakes and reservoirs of the southeastern United States, was found to produce a potent, acutely lethal neurotoxin when tested in the mouse bioassay. Signs of poisoning were similar to those of paralytic shellfish poisoning. As part of the Tennessee Valley Authority master plan for Guntersville Reservoir, the mat-forming filamentous cyanobacterium L. wollei, a species that had recently invaded from other areas of the southern United States, was studied to determine if it could produce any of the known cyanotoxins. Of the 91 field samples collected at 10 locations at Guntersville Reservoir, Ala., on the Tennessee River, over a 3-year period, 72.5% were toxic. The minimum 100% lethal doses of the toxic samples ranged from 150 to 1,500 mg kg of lyophilized L. wollei cells-1, with the majority of samples being toxic at 500 mg kg-1. Samples bioassayed for paralytic shellfish toxins by the Association of Official Analytical Chemists method exhibited saxitoxin equivalents ranging from 0 to 58 micrograms g (dry weight)-1. Characteristics of the neurotoxic compound(s), such as the lack of adsorption by C18 solid-phase extraction columns, the short retention times on C18 high-performance liquid chromatography (HPLC) columns, the interaction of the neurotoxins with saxiphilin (a soluble saxitoxin-binding protein), and external blockage of voltage-sensitive sodium channels, led to our discovery that this neurotoxin(s) is related to the saxitoxins, the compounds responsible for paralytic shellfish poisonings. The major saxitoxin compounds thus far identified by comparison of HPLC fluorescence retention times are decarbamoyl gonyautoxins 2 and 3. There was no evidence of paralytic shellfish poison C toxins being produced by L. wollei. Fifty field samples were placed in unialgal culture and grown under defined culture conditions. Toxicity and signs of poisoning for these

  7. The heterocyst differentiation transcriptional regulator HetR of the filamentous cyanobacterium Anabaena forms tetramers and can be regulated by phosphorylation.

    Science.gov (United States)

    Valladares, Ana; Flores, Enrique; Herrero, Antonia

    2016-02-01

    Many filamentous cyanobacteria respond to the external cue of nitrogen scarcity by the differentiation of heterocysts, cells specialized in the fixation of atmospheric nitrogen in oxic environments. Heterocysts follow a spatial pattern along the filament of two heterocysts separated by ca. 10-15 vegetative cells performing oxygenic photosynthesis. HetR is a transcriptional regulator that directs heterocyst differentiation. In the model strain Anabaena sp. PCC 7120, the HetR protein was observed in various oligomeric forms in vivo, including a tetramer that peaked with maximal hetR expression during differentiation. Tetramers were not detected in a hetR point mutant incapable of differentiation, but were conspicuous in an over-differentiating strain lacking the PatS inhibitor. In differentiated filaments the HetR tetramer was restricted to heterocysts, being undetectable in vegetative cells. HetR co-purified with RNA polymerase from Anabaena mainly as a tetramer. In vitro, purified recombinant HetR was distributed between monomers, dimers, trimers and tetramers, and it was phosphorylated when incubated with (γ-(32)P)ATP. Phosphorylation and PatS hampered the accumulation of HetR tetramers and impaired HetR binding to DNA. In summary, tetrameric HetR appears to represent a functionally relevant form of HetR, whose abundance in the Anabaena filament could be negatively regulated by phosphorylation and by PatS. © 2015 John Wiley & Sons Ltd.

  8. Growth Characteristics of an Estuarine Heterocystous Cyanobacterium

    NARCIS (Netherlands)

    Guimarães, P.; Yunes, J.S.; Cretoiu, M.S.; Stal, L.J.

    2017-01-01

    A new estuarine filamentous heterocystous cyanobacterium was isolated from intertidal sediment of the Lagoa dos Patos estuary (Brazil). The isolate may represent a new genus related to Cylindrospermopsis. While the latter is planktonic, contains gas vesicles, and is toxic, the newly isolated strain

  9. Association of a new type of gliding, filamentous, purple phototrophic bacterium inside bundles of Microcoleus chthonoplastes in hypersaline cyanobacterial mats

    Science.gov (United States)

    D'Amelio, E. D.; Cohen, Y.; Des Marais, D. J.

    1987-01-01

    An unidentified filamentous purple bacterium, probably belonging to a new genus or even a new family, is found in close association with the filamentous, mat-forming cyanobacterium Microcoleus chthonoplastes in a hypersaline pond at Guerrero Negro, Baja California Sur, Mexico, and in Solar Lake, Sinai, Egypt. This organism is a gliding, segmented trichome, 0.8-0.9 micrometer wide. It contains intracytoplasmic stacked lamellae which are perpendicular and obliquely oriented to the cell wall, similar to those described for the purple sulfur bacteria Ectothiorhodospira. These bacteria are found inside the cyanobacterial bundle, enclosed by the cyanobacterial sheath. Detailed transmission electron microscopical analyses carried out in horizontal sections of the upper 1.5 mm of the cyanobacterial mat show this cyanobacterial-purple bacterial association at depths of 300-1200 micrometers, corresponding to the zone below that of maximal oxygenic photosynthesis. Sharp gradients of oxygen and sulfide are established during the day at this microzone in the two cyanobacterial mats studied. The close association, the distribution pattern of this association and preliminary physiological experiments suggest a co-metabolism of sulfur by the two-membered community. This probable new genus of purple bacteria may also grow photoheterotrophically using organic carbon excreted by the cyanobacterium. Since the chemical gradients in the entire photic zone fluctuate widely in a diurnal cycle, both types of metabolism probably take place. During the morning and afternoon, sulfide migrates up to the photic zone allowing photoautotrophic metabolism with sulfide as the electron donor. During the day the photic zone is highly oxygenated and the purple bacteria may either use oxidized species of sulfur such as elemental sulfur and thiosulfate in the photoautotrophic mode or grow photoheterotrophically using organic carbon excreted by M. chthonoplastes. The new type of filamentous purple sulfur

  10. Cell wall amidase AmiC1 is required for cellular communication and heterocyst development in the cyanobacterium Anabaena PCC 7120 but not for filament integrity.

    Science.gov (United States)

    Berendt, Susanne; Lehner, Josef; Zhang, Yao Vincent; Rasse, Tobias M; Forchhammer, Karl; Maldener, Iris

    2012-10-01

    Filamentous cyanobacteria of the order Nostocales display typical properties of multicellular organisms. In response to nitrogen starvation, some vegetative cells differentiate into heterocysts, where fixation of N(2) takes place. Heterocysts provide a micro-oxic compartment to protect nitrogenase from the oxygen produced by the vegetative cells. Differentiation involves fundamental remodeling of the gram-negative cell wall by deposition of a thick envelope and by formation of a neck-like structure at the contact site to the vegetative cells. Cell wall-hydrolyzing enzymes, like cell wall amidases, are involved in peptidoglycan maturation and turnover in unicellular bacteria. Recently, we showed that mutation of the amidase homologue amiC2 gene in Nostoc punctiforme ATCC 29133 distorts filament morphology and function. Here, we present the functional characterization of two amiC paralogues from Anabaena sp. strain PCC 7120. The amiC1 (alr0092) mutant was not able to differentiate heterocysts or to grow diazotrophically, whereas the amiC2 (alr0093) mutant did not show an altered phenotype under standard growth conditions. In agreement, fluorescence recovery after photobleaching (FRAP) studies showed a lack of cell-cell communication only in the AmiC1 mutant. Green fluorescent protein (GFP)-tagged AmiC1 was able to complement the mutant phenotype to wild-type properties. The protein localized in the septal regions of newly dividing cells and at the neck region of differentiating heterocysts. Upon nitrogen step-down, no mature heterocysts were developed in spite of ongoing heterocyst-specific gene expression. These results show the dependence of heterocyst development on amidase function and highlight a pivotal but so far underestimated cellular process, the remodeling of peptidoglycan, for the biology of filamentous cyanobacteria.

  11. Concentration and transport of nitrate by the mat-forming sulphur bacterium Thioploca

    Science.gov (United States)

    Fossing, H.; Gallardo, V. A.; Jørgensen, B. B.; Hüttel, M.; Nielsen, L. P.; Schulz, H.; Canfield, D. E.; Forster, S.; Glud, R. N.; Gundersen, J. K.; Küver, J.; Ramsing, N. B.; Teske, A.; Thamdrup, B.; Ulloa, O.

    1995-04-01

    MARINE species of Thioploca occur over 3,000 km along the continental shelf off Southern Peru and North and Central Chile1-4. These filamentous bacteria live in bundles surrounded by a common sheath and form thick mats on the sea floor under the oxygen-minimum zone in the upwelling region, at between 40 and 280 m water depth. The metabolism of this marine bacterium5,6 remained a mystery until long after its discovery1,7. We report here that Thioploca cells are able to concentrate nitrate to up to 500 mM in a liquid vacuole that occupies >80% of the cell volume. Gliding filaments transport this nitrate 5-10 cm down into the sediment and reduce it, with concomitant oxidation of hydrogen sulphide, thereby coupling the nitrogen and sulphur cycles in the sediment.

  12. A conceptual model for the growth, persistence, and blooming behavior of the benthic mat-forming diatom Didymosphenia geminata (Invited)

    Science.gov (United States)

    Cullis, J. D.; Gillis, C.; Bothwell, M.; Kilroy, C.; Packman, A. I.; Hassan, M. A.

    2010-12-01

    The nuisance diatom Didymosphenia geminata (didymo) presents an ecological paradox. How can this benthic algae produce such large amounts of biomass in cold, fast flowing, low nutrient streams? The aim of this paper is to present a conceptual model for the growth, persistence, and blooming behavior of this benthic mat-forming diatom that may help to explain this paradox. The conceptual model highlights the importance of distinguishing between mat thickness and cell growth. It presents evidence gathered from a range of existing studies around the world to support the proposed relationship between growth and light, nutrients and temperature as well as the importance of flood events and bed disturbance in mat removal. It is anticipated that this conceptual model will not only help in identifying the key controlling variables and set a framework for future studies but also support the future management of this nuisance algae. Summary of the conceptual model for didymo growth showing the proposed relationships for the growth of cells and mats with nutrients, radiation and water temperature and the dependence of removal on bed shear stress and the potential for physical bed disturbance.

  13. Diversity of Mat-Forming Fungi in Relation to Soil Properties, Disturbance, and Forest Ecotype at Crater Lake National Park, Oregon, USA

    Directory of Open Access Journals (Sweden)

    James M. Trappe

    2012-04-01

    Full Text Available In forest ecosystems, fungal mats are functionally important in nutrient and water uptake in litter and wood decomposition processes, in carbon resource allocation, soil weathering and in cycling of soil resources. Fungal mats can occur abundantly in forests and are widely distributed globally. We sampled ponderosa pine/white fir and mountain hemlock/noble fir communities at Crater Lake National Park for mat-forming soil fungi. Fungus collections were identified by DNA sequencing. Thirty-eight mat-forming genotypes were identified; members of the five most common genera (Gautieria, Lepiota, Piloderma, Ramaria, and Rhizopogon comprised 67% of all collections. The mycorrhizal genera Alpova and Lactarius are newly identified as ectomycorrhizal mat-forming taxa, as are the saprotrophic genera Flavoscypha, Gastropila, Lepiota and Xenasmatella. Twelve typical mat forms are illustrated, representing both ectomycorrhizal and saprotrophic fungi that were found. Abundance of fungal mats was correlated with higher soil carbon to nitrogen ratios, fine woody debris and needle litter mass in both forest ecotypes. Definitions of fungal mats are discussed, along with some of the challenges in defining what comprises a fungal “mat”.

  14. Nostoc PCC7524, a cyanobacterium which contains five sequence-specific deoxyribonucleases

    NARCIS (Netherlands)

    Reaston, J.; Duybesteyn, M.G.C.; Waard, Adrian de

    1982-01-01

    Five nucleotide sequence-specific deoxyribonucleases present in cell-free extracts of the filamentous cyanobacterium Nostoc PCC7524 have been purified and characterized. One of these enzymes, designated Nsp(7524)I cleaves at a new kind of nucleotide sequence i.e. 5'-PuCATG λ Py-3'. The other four

  15. Horizontal transfer of the nitrogen fixation gene cluster in the cyanobacterium Microcoleus chthonoplastes

    NARCIS (Netherlands)

    Bolhuis, H.; Severin, I.; Confurius-Guns, V.; Wollenzien, U.I.A.; Stal, L.J.

    2010-01-01

    The filamentous, non-heterocystous cyanobacterium Microcoleus chthonoplastes is a cosmopolitan organism, known to build microbial mats in a variety of different environments. Although most of these cyanobacterial mats are known for their capacity to fix dinitrogen, M. chthonoplastes has not been

  16. Dissolved organic nitrogen and carbon release by a marine unicellular diazotrophic cyanobacterium

    NARCIS (Netherlands)

    Benavides, M.; Agawin, N.S.R.; Aristegui, J.; Peene, J.; Stal, L.J.

    2013-01-01

    Dinitrogen (N-2) fixation rates may be underestimated when recently fixed N2 is released as dissolved organic nitrogen (DON). DON release (DONr) is substantial in the filamentous cyanobacterium Trichodesmium but has never been reported in unicellular diazotrophic cyanobacteria. We used axenic

  17. Dissolved organic nitrogen and carbon release by a marine unicellular diazotrophic cyanobacterium

    NARCIS (Netherlands)

    Benavides, M.; Agawin, N.S.R.; Aristegui, J.; Peene, J.; Stal, L.J.

    2013-01-01

    Dinitrogen (N2) fixation rates may be underestimated when recently fixed N2 is released as dissolved organic nitrogen (DON). DON release (DONr) is substantial in the filamentous cyanobacterium Trichodesmium but has never been reported in unicellular diazotrophic cyanobacteria. We used axenic

  18. Concentration and Transport of Nitrate by the Mat-Forming Sulfur Bacterium Thioploca Rid E-1821-2011

    DEFF Research Database (Denmark)

    FOSSING, H.; GALLARDO, VA; JØRGENSEN, BB

    1995-01-01

    MARINE species of Thioploca occur over 3,000 km along the continental shelf off Southern Peru and North and Central Chile(1-4). These filamentous bacteria live in bundles surrounded by a common sheath and form thick mats on the sea floor under the oxygen-minimum zone in the upwelling region......, at between 40 and 280 m water depth. The metabolism of this marine bacterium(5,6) remained a mystery until long after its discovery(1,7). We report here that Thioploca cells are able to concentrate nitrate to up to 500 mM in a liquid vacuole that occupies >80% of the cell volume. Gliding filaments transport...... this nitrate 5-10 cm down into the sediment and reduce it, with concomitant oxidation of hydrogen sulphide, thereby coupling the nitrogen and sulphur cycles in the sediment....

  19. Identifying the interacting roles of stressors in driving the global loss of canopy-forming to mat-forming algae in marine ecosystems.

    Science.gov (United States)

    Strain, Elisabeth M A; Thomson, Russell J; Micheli, Fiorenza; Mancuso, Francesco P; Airoldi, Laura

    2014-11-01

    Identifying the type and strength of interactions between local anthropogenic and other stressors can help to set achievable management targets for degraded marine ecosystems and support their resilience by identifying local actions. We undertook a meta-analysis, using data from 118 studies to test the hypothesis that ongoing global declines in the dominant habitat along temperate rocky coastlines, forests of canopy-forming algae and/or their replacement by mat-forming algae are driven by the nonadditive interactions between local anthropogenic stressors that can be addressed through management actions (fishing, heavy metal pollution, nutrient enrichment and high sediment loads) and other stressors (presence of competitors or grazers, removal of canopy algae, limiting or excessive light, low or high salinity, increasing temperature, high wave exposure and high UV or CO2 ), not as easily amenable to management actions. In general, the cumulative effects of local anthropogenic and other stressors had negative effects on the growth and survival of canopy-forming algae. Conversely, the growth or survival of mat-forming algae was either unaffected or significantly enhanced by the same pairs of stressors. Contrary to our predictions, the majority of interactions between stressors were additive. There were however synergistic interactions between nutrient enrichment and heavy metals, the presence of competitors, low light and increasing temperature, leading to amplified negative effects on canopy-forming algae. There were also synergistic interactions between nutrient enrichment and increasing CO2 and temperature leading to amplified positive effects on mat-forming algae. Our review of the current literature shows that management of nutrient levels, rather than fishing, heavy metal pollution or high sediment loads, would provide the greatest opportunity for preventing the shift from canopy to mat-forming algae, particularly in enclosed bays or estuaries because of the

  20. Genetically modified cyanobacterium Nostoc muscorum ...

    Indian Academy of Sciences (India)

    Madhu

    diazotrophic cultures of the cyanobacterium N. muscorum in quantities of 5 .... growth media and then used for estimation of their characteristics. Each reading is ..... 1224–1232. Christian J H B 1950 The influence of nutrition on the water rela-.

  1. Plectolyngbya hodgsonii: a novel filamentous cyanobacterium from Antarctic lakes

    Czech Academy of Sciences Publication Activity Database

    Taton, A.; Wilmotte, A.; Šmarda, J.; Elster, Josef; Komárek, Jiří

    2011-01-01

    Roč. 34, č. 2 (2011), 181-191 ISSN 0722-4060 R&D Projects: GA ČR GA206/05/0253 Institutional research plan: CEZ:AV0Z60050516 Keywords : Antarctica * benthos of lake * cyanobacteria Subject RIV: EF - Botanics Impact factor: 1.659, year: 2011

  2. Growth Characteristics of an Estuarine Heterocystous Cyanobacterium

    Directory of Open Access Journals (Sweden)

    Pablo Guimarães

    2017-06-01

    Full Text Available A new estuarine filamentous heterocystous cyanobacterium was isolated from intertidal sediment of the Lagoa dos Patos estuary (Brazil. The isolate may represent a new genus related to Cylindrospermopsis. While the latter is planktonic, contains gas vesicles, and is toxic, the newly isolated strain is benthic and does not contain gas vesicles. It is not known whether the new strain is toxic. It grows equally well in freshwater, brackish and full salinity growth media, in the absence of inorganic or organic combined nitrogen, with a growth rate 0.6 d-1. Nitrogenase, the enzyme complex responsible for fixing dinitrogen, was most active during the initial growth phase and its activity was not different between the different salinities tested (freshwater, brackish, and full salinity seawater. Salinity shock also did not affect nitrogenase activity. The frequency of heterocysts was high, coinciding with high nitrogenase activity during the initial growth phase, but decreased subsequently. However, the frequency of heterocysts decreased considerably more at higher salinity, while no change in nitrogenase activity occurred, indicating a higher efficiency of dinitrogen fixation. Akinete frequency was low in the initial growth phase and higher in the late growth phase. Akinete frequency was much lower at high salinity, which might indicate better growth conditions or that akinete differentiation was under the same control as heterocyst differentiation. These trends have hitherto not been reported for heterocystous cyanobacteria but they seem to be well fitted for an estuarine life style.

  3. Helical filaments

    Energy Technology Data Exchange (ETDEWEB)

    Barbieri, Nicholas; Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin [Townes Laser Institute, CREOL—The College of Optics and Photonics, University of Central Florida, Orlando, Florida 32816 (United States); Hosseinimakarem, Zahra; Johnson, Eric [Micro-Photonics Laboratory – Center for Optical Material Science, Clemson, Anderson, South Carolina 29634 (United States)

    2014-06-30

    The shaping of laser-induced filamenting plasma channels into helical structures by guiding the process with a non-diffracting beam is demonstrated. This was achieved using a Bessel beam superposition to control the phase of an ultrafast laser beam possessing intensities sufficient to induce Kerr effect driven non-linear self-focusing. Several experimental methods were used to characterize the resulting beams and confirm the observed structures are laser air filaments.

  4. A conceptual model for the blooming behavior and persistence of the benthic mat-forming diatom Didymosphenia geminata in oligotrophic streams

    Science.gov (United States)

    Cullis, James D. S.; Gillis, Carole-Anne; Bothwell, Max L.; Kilroy, Cathy; Packman, Aaron; Hassan, Marwan

    2012-06-01

    The benthic, mat-forming diatomDidymosphenia geminata has the unique ability to produce large amounts of algal biomass under oligotrophic conditions in cold, fast flowing streams and rivers. This presents an ecological paradox that challenges our current understanding of stream ecosystem dynamics. Our understanding of the drivers of D. geminata ecology is still limited. Here we present a conceptual model for the blooming behavior and persistence of this species to advance scientific understanding of strategies for life in fast flowing oligotrophic waters and support the design of future research and mitigation measures for nuisance algal blooms. The conceptual model is based on a synthesis of data and ideas from a range of disciplines including hydrology, geomorphology, biogeochemistry, and ecology. The conceptual model highlights the role of water chemistry, river morphology, and flow thresholds in defining the habitat window for D. geminata. We propose that bed disturbance is a primary control on accumulation and persistence of D. geminataand that the removal threshold can be determined by synthesizing site-specific information on hydrology and geomorphology. Further, we propose that a key to understanding the didymo paradox is the separation of cellular reproduction and mat morphology with specific controls acting in respect of the different processes.

  5. Filamentous Fungi.

    Science.gov (United States)

    Powers-Fletcher, Margaret V; Kendall, Brian A; Griffin, Allen T; Hanson, Kimberly E

    2016-06-01

    Filamentous mycoses are often associated with significant morbidity and mortality. Prompt diagnosis and aggressive treatment are essential for good clinical outcomes in immunocompromised patients. The host immune response plays an essential role in determining the course of exposure to potential fungal pathogens. Depending on the effectiveness of immune response and the burden of organism exposure, fungi can either be cleared or infection can occur and progress to a potentially fatal invasive disease. Nonspecific cellular immunity (i.e., neutrophils, natural killer [NK] cells, and macrophages) combined with T-cell responses are the main immunologic mechanisms of protection. The most common potential mold pathogens include certain hyaline hyphomycetes, endemic fungi, the Mucorales, and some dematiaceous fungi. Laboratory diagnostics aimed at detecting and differentiating these organisms are crucial to helping clinicians make informed decisions about treatment. The purpose of this chapter is to provide an overview of the medically important fungal pathogens, as well as to discuss the patient characteristics, antifungal-therapy considerations, and laboratory tests used in current clinical practice for the immunocompromised host.

  6. Nitrogen uptake dynamics of a persistent cyanobacterium ...

    African Journals Online (AJOL)

    Worldwide, persistent cyanobacterial blooms are becoming more frequent and are often associated with effects of global climate change. In June 2009, a widespread bloom of the unicellular cyanobacterium, Cyanothece sp., appeared in North Lake and False Bay of Lake St Lucia – a large (360 km2) estuarine lake system ...

  7. Photoacclimation of cultured strains of the cyanobacterium

    NARCIS (Netherlands)

    Bañares-España, E.; Kromkamp, J.C.; López-Rodas, V.; Costas, E.; Flores-Moya, A.

    2013-01-01

    The cyanobacterium Microcystis aeruginosa forms blooms that can consist of colonies. We have investigated how M.aeruginosa acclimatizes to changing light conditions such as can occur during blooms. Three different strains were exposed to two irradiance levels: lower (LL) and higher (HL) than the

  8. Antagonism at combined effects of chemical fertilizers and carbamate insecticides on the rice-field N2-fixing cyanobacterium Cylindrospermum sp. in vitro

    OpenAIRE

    Padhy Rabindra N.; Nayak Nabakishore; Rath Shakti

    2014-01-01

    Effects of chemical fertilizers (urea, super phosphate and potash) on toxicities of two carbamate insecticides, carbaryl and carbofuran, individually to the N2-fixing cyanobacterium, Cylindrospermum sp. were studied in vitro at partially lethal levels (below highest permissive concentrations) of each insecticide. The average number of vegetative cells between two polar heterocysts was 16.3 in control cultures, while the mean value of filament length increased in the presence of chemical ferti...

  9. Solar Features - Prominences and Filaments - Filaments

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Filaments are formed in magnetic loops that hold relatively cool, dense gas suspended above the surface of the Sun (David Hathaway/NASA)

  10. Cellular and functional specificity among ferritin-like proteins in the multicellular cyanobacterium Nostoc punctiforme.

    Science.gov (United States)

    Ekman, Martin; Sandh, Gustaf; Nenninger, Anja; Oliveira, Paulo; Stensjö, Karin

    2014-03-01

    Ferritin-like proteins constitute a remarkably heterogeneous protein family, including ferritins, bacterioferritins and Dps proteins. The genome of the filamentous heterocyst-forming cyanobacterium Nostoc punctiforme encodes five ferritin-like proteins. In the present paper, we report a multidimensional characterization of these proteins. Our phylogenetic and bioinformatics analyses suggest both structural and physiological differences among the ferritin-like proteins. The expression of these five genes responded differently to hydrogen peroxide treatment, with a significantly higher rise in transcript level for Npun_F3730 as compared with the other four genes. A specific role for Npun_F3730 in the cells tolerance against hydrogen peroxide was also supported by the inactivation of Npun_F3730, Npun_R5701 and Npun_R6212; among these, only the ΔNpun_F3730 strain showed an increased sensitivity to hydrogen peroxide compared with wild type. Analysis of promoter-GFP reporter fusions of the ferritin-like genes indicated that Npun_F3730 and Npun_R5701 were expressed in all cell types of a diazotrophic culture, while Npun_F6212 was expressed specifically in heterocysts. Our study provides the first comprehensive analysis combining functional differentiation and cellular specificity within this important group of proteins in a multicellular cyanobacterium. © 2013 John Wiley & Sons Ltd and Society for Applied Microbiology.

  11. Arsenic biotransformation by a cyanobacterium Nostoc sp. PCC 7120.

    Science.gov (United States)

    Xue, Xi-Mei; Yan, Yu; Xiong, Chan; Raber, Georg; Francesconi, Kevin; Pan, Ting; Ye, Jun; Zhu, Yong-Guan

    2017-09-01

    Nostoc sp. PCC 7120 (Nostoc), a typical filamentous cyanobacterium ubiquitous in aquatic system, is recognized as a model organism to study prokaryotic cell differentiation and nitrogen fixation. In this study, Nostoc cells incubated with arsenite (As(III)) for two weeks were extracted with dichloromethane/methanol (DCM/MeOH) and the extract was partitioned between water and DCM. Arsenic species in aqueous and DCM layers were determined using high performance liquid chromatography - inductively coupled plasma mass spectrometer/electrospray tandem mass spectrometry (HPLC-ICPMS/ESIMSMS). In addition to inorganic arsenic (iAs), the aqueous layer also contained monomethylarsonate (MAs(V)), dimethylarsinate (DMAs(V)), and the two arsenosugars, namely a glycerol arsenosugar (Oxo-Gly) and a phosphate arsenosugar (Oxo-PO4). Two major arsenosugar phospholipids (AsSugPL982 and AsSugPL984) were detected in DCM fraction. Arsenic in the growth medium was also investigated by HPLC/ICPMS and shown to be present mainly as the inorganic forms As(III) and As(V) accounting for 29%-38% and 29%-57% of the total arsenic respectively. The total arsenic of methylated arsenic, arsenosugars, and arsenosugar phospholipids in Nostoc cells with increasing As(III) exposure were not markedly different, indicating that the transformation to organoarsenic in Nostoc was not dependent on As(III) concentration in the medium. Our results provide new insights into the role of cyanobacteria in the biogeochemical cycling of arsenic. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. BMAA Inhibits Nitrogen Fixation in the Cyanobacterium Nostoc sp. PCC 7120

    Directory of Open Access Journals (Sweden)

    Birgitta Bergman

    2013-08-01

    Full Text Available Cyanobacteria produce a range of secondary metabolites, one being the neurotoxic non-protein amino acid β-N-methylamino-L-alanine (BMAA, proposed to be a causative agent of human neurodegeneration. As for most cyanotoxins, the function of BMAA in cyanobacteria is unknown. Here, we examined the effects of BMAA on the physiology of the filamentous nitrogen-fixing cyanobacterium Nostoc sp. PCC 7120. Our data show that exogenously applied BMAA rapidly inhibits nitrogenase activity (acetylene reduction assay, even at micromolar concentrations, and that the inhibition was considerably more severe than that induced by combined nitrogen sources and most other amino acids. BMAA also caused growth arrest and massive cellular glycogen accumulation, as observed by electron microscopy. With nitrogen fixation being a process highly sensitive to oxygen species we propose that the BMAA effects found here may be related to the production of reactive oxygen species, as reported for other organisms.

  13. Inhibition of motility in the cyanobacterium, Phormidium uncinatum, by solar and monochromatic UV irradiation

    International Nuclear Information System (INIS)

    Häder, D.P.; Watanabe, M.; Furuya, M.

    1986-01-01

    The effect of solar radiation and monochromatic UV radiation on the motility of the filamentous cyanobacterium Phormidium uncinatum was determined. Solar radiation (mid-day, in midsummer at a location near Lisboa, Portugal) was found to impair motility within about 30 min. This effect is neither a result of a temperature increase nor of visible light. The spectral sensitivity determined using the Okazaki Largé Spectrograph shows the maximal effectiveness of radiation of ≤300 nm. The short time requirement for the response and the lack of any photoreactivation of motility argues against DNA being the UV target. Investigations using reagents diagnostic of superoxide free radicals and singlet oxygen failed to confirm the involvement of photodynamic effects as the molecular mechanism causing UV inhibition of motility

  14. BMAA Inhibits Nitrogen Fixation in the Cyanobacterium Nostoc sp. PCC 7120

    Science.gov (United States)

    Berntzon, Lotta; Erasmie, Sven; Celepli, Narin; Eriksson, Johan; Rasmussen, Ulla; Bergman, Birgitta

    2013-01-01

    Cyanobacteria produce a range of secondary metabolites, one being the neurotoxic non-protein amino acid β-N-methylamino-L-alanine (BMAA), proposed to be a causative agent of human neurodegeneration. As for most cyanotoxins, the function of BMAA in cyanobacteria is unknown. Here, we examined the effects of BMAA on the physiology of the filamentous nitrogen-fixing cyanobacterium Nostoc sp. PCC 7120. Our data show that exogenously applied BMAA rapidly inhibits nitrogenase activity (acetylene reduction assay), even at micromolar concentrations, and that the inhibition was considerably more severe than that induced by combined nitrogen sources and most other amino acids. BMAA also caused growth arrest and massive cellular glycogen accumulation, as observed by electron microscopy. With nitrogen fixation being a process highly sensitive to oxygen species we propose that the BMAA effects found here may be related to the production of reactive oxygen species, as reported for other organisms. PMID:23966039

  15. Lake viruses lyse cyanobacteria, Cylindrospermopsis raciborskii, enhances filamentous-host dispersal in Australia

    Science.gov (United States)

    Pollard, Peter C.; Young, Loretta M.

    2010-01-01

    Globally, cyanobacterial blooms are increasing along with observations of the controlling influence of viruses. Our aim here was to test whether viruses from an Australian freshwater lake could lyse the cyanobacterium Cylindrospermopsis raciborskii (Woloszynska) Seenaya and Subba Raju. C. raciborskii was selectively isolated from Lake Samsonvale southeast Queensland Australia using a Modified Jaworski Medium (without any form of inorganic nitrogen). Microscopy confirmed the resulting culture of a single cyanobacterial species. Natural viral-like particles (VLPs) were incubated with C. raciborskii cells, the host abundance decreased by 86% in 5 days, while the number of VLPs increased stepwise. As a cell lysed, the filaments of cells split into smaller, but viable, fragments. This process may help disperse the cyanobacterium in the wild. Hence the use of this virus to control blooms may inadvertently encourage the dispersal of toxic filamentous cyanobacteria. The cyanophage (virus infecting cyanobacteria) replication time was 21 h, with an average burst size of 64 viruses cell -1. Transmission Electron Microscopy showed this cyanophage for C. raciborskii, with its long, non-contractile tail and a capsid diameter of 70 nm, belongs to the Siphoviridae family of viruses. This cyanophage can affect the abundance and distribution of the cyanobacterium C. raciborskii in this Australian freshwater lake.

  16. Tungsten Filament Fire

    Science.gov (United States)

    Ruiz, Michael J.; Perkins, James

    2016-01-01

    We safely remove the outer glass bulb from an incandescent lamp and burn up the tungsten filament after the glass is removed. This demonstration dramatically illustrates the necessity of a vacuum or inert gas for the environment surrounding the tungsten filament inside the bulb. Our approach has added historical importance since the incandescent…

  17. Proteomics of Filamentous Fungi

    NARCIS (Netherlands)

    Passel, van M.W.J.; Schaap, P.J.; Graaff, de L.H.

    2013-01-01

    Filamentous fungi, such as Aspergillus niger and Aspergillus oryzae traditionally have had an important role in providing enzymes and enzyme cocktails that are used in food industry. In recent years the genome sequences of many filamentous fungi have become available. This combined with

  18. SYMPATHETIC SOLAR FILAMENT ERUPTIONS

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Rui; Liu, Ying D.; Zimovets, Ivan; Hu, Huidong; Yang, Zhongwei [State Key Laboratory of Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing 100190 (China); Dai, Xinghua, E-mail: liuxying@spaceweather.ac.cn [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China)

    2016-08-10

    The 2015 March 15 coronal mass ejection as one of the two that together drove the largest geomagnetic storm of solar cycle 24 so far was associated with sympathetic filament eruptions. We investigate the relations between the different filaments involved in the eruption. A surge-like small-scale filament motion is confirmed as the trigger that initiated the erupting filament with multi-wavelength observations and using a forced magnetic field extrapolation method. When the erupting filament moved to an open magnetic field region, it experienced an obvious acceleration process and was accompanied by a C-class flare and the rise of another larger filament that eventually failed to erupt. We measure the decay index of the background magnetic field, which presents a critical height of 118 Mm. Combining with a potential field source surface extrapolation method, we analyze the distributions of the large-scale magnetic field, which indicates that the open magnetic field region may provide a favorable condition for F2 rapid acceleration and have some relation with the largest solar storm. The comparison between the successful and failed filament eruptions suggests that the confining magnetic field plays an important role in the preconditions for an eruption.

  19. Evolution of Filament Barbs

    OpenAIRE

    Liu, Rui; Xu, Yan; Wang, Haimin

    2010-01-01

    We present a selected few cases in which the sense of chirality of filament barbs changed within as short as hours. We investigate in detail a quiescent filament on 2003 September 10 and 11. Of its four barbs displaying such changes only one overlay a small polarity inversion line inside the EUV filament channel (EFC). No magnetic elements with magnitude above the noise level were detected at the endpoints of all barbs. In particular, a pair of barbs first approached toward and then departed ...

  20. Bacterial intermediate filaments

    DEFF Research Database (Denmark)

    Charbon, Godefroid; Cabeen, M.; Jacobs-Wagner, C.

    2009-01-01

    Crescentin, which is the founding member of a rapidly growing family of bacterial cytoskeletal proteins, was previously proposed to resemble eukaryotic intermediate filament (IF) proteins based on structural prediction and in vitro polymerization properties. Here, we demonstrate that crescentin...

  1. Femtosecond Laser Filamentation

    CERN Document Server

    Chin, See Leang

    2010-01-01

    Femtosecond Laser Filamentation gives a comprehensive review of the physics of propagation of intense femtosecond laser pulses in optical media (principally air) and the applications and challenges of this new technique. This book presents the modern understanding of the physics of femtosecond laser pulse propagation, including unusual new effects such as the self-transformation of the pulse into a white light laser pulse, intensity clamping, the physics of multiple filamentation and competition, and how filaments’ ability to melt glass leads to wave guide writing. The potential applications of laser filamentation in atmospheric sensing and the generation of other electromagnetic pulses from the UV to the radio frequency are treated, together with possible future challenges in the excitation of super-excited states of molecules. Exciting new phenomena such as filament induced ultrafast birefringence and the excitation of molecular rotational wave packets and their multiple revivals in air (gases) will also ...

  2. Biogeochemical tracers of the marine cyanobacterium Trichodesmium

    Science.gov (United States)

    Carpenter, Edward J.; Harvey, H. Rodger; Fry, Brian; Capone, Douglas G.

    1997-01-01

    We examined the utility of several biogeochemical tracers for following the fate of the planktonic diazotrophic cyanobacterium Trichodesmium in the sea. The presence of a (CIO) fatty acid previously reported was observed in a culture of Trichodesmium but was not found in natural samples. This cyanobacterium had high concentrations of C 14 and C 16 acids, with lesser amounts of several saturated and unsaturated C 18 fatty acids. This composition was similar to that of other marine cyanobacteria. The major hydrocarbon identified was the C 17n-alkane, which was present in all samples from the five stations examined. Sterols common to algae and copepods were observed in many samples along with hopanoids representative of bacteria, suggesting a varied community structure in colonies collected from different stations. We found no unique taxonomic marker of Trichodesmium among the sterols. Measurements of the σ 15N and σ 13C in Trichodesmium samples from the SW Sargasso and NW Caribbean Seas averaged -0.4960 (range from -0.7 to -0.25960) and -12.9%0 (range from -15.2 to -11.9960), respectively, thus confirming previous observations that this cyanobacterial diazotroph has both the lowest σ 15N and highest σ 13C of any marine phytoplankter observed to date. A culture of Trichodesmium grown under diazotrophic conditions had a σ 15N between -1.3 and -3.6960. Our results support the supposition that the relatively low σ 15N and high σ 13C values observed in suspended and sediment-trapped material from some tropical and subtropical seas result from substantial input of C and N by Trichodesmium.

  3. Fundamentals of Filament Interaction

    Science.gov (United States)

    2017-05-19

    AFRL-AFOSR-VA-TR-2017-0110 FUNDAMENTALS OF FILAMENT INTERACTION Martin Richardson UNIVERSITY OF CENTRAL FLORIDA Final Report 06/02/2017 DISTRIBUTION...of Filament Interaction 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA95501110001 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Martin Richardson 5d. PROJECT...NAME OF RESPONSIBLE PERSON Martin Richardson a. REPORT b. ABSTRACT c. THIS PAGE 19b. TELEPHONE NUMBER (Include area code) 407-823-6819 Standard Form

  4. Colored fused filament fabrication

    OpenAIRE

    Song, Haichuan; Lefebvre, Sylvain

    2017-01-01

    Filament fused fabrication is the method of choice for printing 3D models at low cost, and is the de-facto standard for hobbyists, makers and schools. Unfortunately, filament printers cannot truly reproduce colored objects. The best current techniques rely on a form of dithering exploiting occlusion, that was only demonstrated for shades of two base colors and that behaves differently depending on surface slope. We explore a novel approach for 3D printing colored objects, capable of creating ...

  5. ORGANIZATION OF THE nif GENES OF THE NONHETEROCYSTOUS CYANOBACTERIUM TRICHODESMIUM SP. IMS101.

    Science.gov (United States)

    Dominic, Benny; Zani, Sabino; Chen, Yi-Bu; Mellon, Mark T; Zehr, Jonathan P

    2000-08-26

    An approximately 16-kb fragment of the Trichodesmium sp. IMS101 (a nonheterocystous filamentous cyanobacterium) "conventional"nif gene cluster was cloned and sequenced. The gene organization of the Trichodesmium and Anabaena variabilis vegetative (nif 2) nitrogenase gene clusters spanning the region from nif B to nif W are similar except for the absence of two open reading frames (ORF3 and ORF1) in Trichodesmium. The Trichodesmium nif EN genes encode a fused Nif EN polypeptide that does not appear to be processed into individual Nif E and Nif N polypeptides. Fused nif EN genes were previously found in the A. variabilis nif 2 genes, but we have found that fused nif EN genes are widespread in the nonheterocystous cyanobacteria. Although the gene organization of the nonheterocystous filamentous Trichodesmium nif gene cluster is very similar to that of the A. variabilis vegetative nif 2 gene cluster, phylogenetic analysis of nif sequences do not support close relatedness of Trichodesmium and A. variabilis vegetative (nif 2) nitrogenase genes.

  6. Filament Substructures and their Interrelation

    Science.gov (United States)

    Lin, Y.; Martin, S. F.; Engvold, O.

    The main structural components of solar filaments, their spines, barbs, and legs at the extreme ends of the spine, are illustrated from recent high-resolution observations. The thread-like structures appear to be present in filaments everywhere and at all times. They are the fundamental elements of solar filaments. The interrelation of the spines, barbs and legs are discussed. From observations, we present a conceptual model of the magnetic field of a filament. We suggest that only a single physical model is needed to explain filaments in a continuous spectrum represented by active region filaments at one end and quiescent filaments at the other end.

  7. Effect of UV-B on enzymes of nitrogen metabolism in the cyanobacterium Nostoc calcicola

    International Nuclear Information System (INIS)

    Kumar, A.; Sinha, R.P.; Häder, D. P.

    1996-01-01

    The effects of ultraviolet-B (UV-B; 280–315 nm) irradiation on nitrogenase and nitrate reductase (NR) activity have been studied in the filamentous and heterocystous N 2 -fixing cyanobacterium Nostoc calcicola. Exposure of cultures to UV-B (5W/m 2 ) for as little as 30 min caused complete inactivation of nitrogenase activity whereas nitrate reductase activity was stimulated twofold in comparison to one exposed to fluorescent white light. GS activity was also inhibited by UV-B treatment, but there was no total loss of activity even after 4 h. NR activity showed a gradual stimulation up to 4 h and thereafter it became constant. Stimulation was also obtained in reductant deficient cultures (12 h incubation in the dark) suggesting independence of NR of PS-II under UV-B. NR activity was also unaffected in the presence of DCMU, a known inhibitor of PS-II. However, both O 2 evolution and 14 CO 2 uptake were completely abolished following 30 min of UV-B treatment. Addition of the protein synthesis inhibitor chloramphenicol (25 μg/mL) to cultures did not show any inhibitory effect on NR activity. SDS-PAGE analysis of UV-B treated cultures elicited gradual loss of protein bands with increasing duration of exposure. Our findings suggest that UV-B irradiance has differential effects on the enzymes of the nitrogen metabolism in the cyanobacterium Nostoc calcicola. Further studies are needed to reveal the exact mechanism involved in the stimulation of NR activity by UV-B. Whether UV-B has a direct effect on NO 2 − accumulation in the cells needs detailed investigation. (author)

  8. Evolution of filament barbs.

    Science.gov (United States)

    Liu, R.; Xu, Y.; Wang, H.

    We present a selected few cases in which the sense of chirality of filament barbs changed within periods as short as hours. We investigate in detail a quiescent filament on 2003 September 10 and 11. Of its four barbs displaying such changes, only one overlays a small polarity inversion line inside the EUV filament channel (EFC). No magnetic elements with magnitude above the noise level were detected at the endpoints of all barbs. In particular, a pair of barbs first approached toward, and then departed from, each other in Halpha , with the barb endpoints migrating as far as ˜ 10 arcsec. We conclude that the evolution of the barbs was driven by flux emergence and cancellation of small bipolar units at the EFC border.

  9. Filaments in Lupus I

    Science.gov (United States)

    Takahashi, Satoko; Rodon, J.; De Gregorio-Monsalvo, I.; Plunkett, A.

    2017-06-01

    The mechanisms behind the formation of sub-stellar mass sources are key to determine the populations at the low-mass end of the stellar distribution. Here, we present mapping observations toward the Lupus I cloud in C18O(2-1) and 13CO(2-1) obtained with APEX. We have identified a few velocity-coherent filaments. Each contains several substellar mass sources that are also identified in the 1.1mm continuum data (see also SOLA catalogue presentation). We will discuss the velocity structure, fragmentation properties of the identified filaments, and the nature of the detected sources.

  10. Arabinogalactan proteins occur in the free-living cyanobacterium genus Nostoc and in plant-Nostoc symbioses.

    Science.gov (United States)

    Jackson, Owen; Taylor, Oliver; Adams, David G; Knox, J Paul

    2012-10-01

    Arabinogalactan proteins (AGP) are a diverse family of proteoglycans associated with the cell surfaces of plants. AGP have been implicated in a wide variety of plant cell processes, including signaling in symbioses. This study investigates the existence of putative AGP in free-living cyanobacterial cultures of the nitrogen-fixing, filamentous cyanobacteria Nostoc punctiforme and Nostoc sp. strain LBG1 and at the symbiotic interface in the symbioses between Nostoc spp. and two host plants, the angiosperm Gunnera manicata (in which the cyanobacterium is intracellular) and the liverwort Blasia pusilla (in which the cyanobacterium is extracellular). Enzyme-linked immunosorbent assay, immunoblotting, and immunofluorescence analyses demonstrated that three AGP glycan epitopes (recognized by monoclonal antibodies LM14, MAC207, and LM2) are present in free-living Nostoc cyanobacterial species. The same three AGP glycan epitopes are present at the Gunnera-Nostoc symbiotic interface and the LM2 epitope is detected during the establishment of the Blasia-Nostoc symbiosis. Bioinformatic analysis of the N. punctiforme genome identified five putative AGP core proteins that are representative of AGP classes found in plants. These results suggest a possible involvement of AGP in cyanobacterial-plant symbioses and are also suggestive of a cyanobacterial origin of AGP.

  11. Solar Features - Prominences and Filaments

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Prominences and filaments are two manifestations of the same phenomenon. Both prominences and filaments are features formed above the chromosphere by cool dense...

  12. Permanent Draft Genome of Strain ESFC-1: Ecological Genomics of a Newly Discovered Lineage of Filamentous Diazotrophic Cyanobacteria

    Science.gov (United States)

    Everroad, R. Craig; Stuart, Rhona K.; Bebout, Brad M.; Detweiler, Angela M.; Lee, Jackson Zan; Woebken, Dagmar; Bebout, Leslie E.; Pett-Ridge, Jennifer

    2016-01-01

    The nonheterocystous filamentous cyanobacterium, strain ESFC-1, is a recently described member of the order Oscillatoriales within the Cyanobacteria. ESFC-1 has been shown to be a major diazotroph in the intertidal microbial mat system at Elkhorn Slough, CA, USA. Based on phylogenetic analyses of the 16S RNA gene, ESFC-1 appears to belong to a unique, genus-level divergence; the draft genome sequence of this strain has now been determined. Here we report features of this genome as they relate to the ecological functions and capabilities of strain ESFC-1. The 5,632,035 bp genome sequence encodes 4914 protein-coding genes and 92 RNA genes. One striking feature of this cyanobacterium is the apparent lack of either uptake or bi-directional hydrogenases typically expected within a diazotroph. Additionally, a large genomic island is found that contains numerous low GC-content genes and genes related to extracellular polysaccharide production and cell wall synthesis and maintenance.

  13. Filamentous Fungi Fermentation

    DEFF Research Database (Denmark)

    Nørregaard, Anders; Stocks, Stuart; Woodley, John

    2014-01-01

    Filamentous fungi (including microorganisms such as Aspergillus niger and Rhizopus oryzae) represent an enormously important platform for industrial fermentation. Two particularly valuable features are the high yield coefficients and the ability to secrete products. However, the filamentous...... morphology, together with non-Newtonian rheological properties (shear thinning), result in poor oxygen transfer unless sufficient energy is provided to the fermentation. While genomic research may improve the organisms, there is no doubt that to enable further application in future it will be necessary...... to match such research with studies of oxygen transfer and energy supply to high viscosity fluids. Hence, the implementation of innovative solutions (some of which in principle are already possible) will be essential to ensure the further development of such fermentations....

  14. Filament heater current modulation for increased filament lifetime

    International Nuclear Information System (INIS)

    Paul, J.D.; Williams, H.E. III.

    1996-01-01

    The surface conversion H-minus ion source employs two 60 mil tungsten filaments which are approximately 17 centimeters in length. These filaments are heated to approximately 2,800 degrees centigrade by 95--100 amperes of DC heater current. The arc is struck at a 120 hertz rate, for 800 microseconds and is generally run at 30 amperes peak current. Although sputtering is considered a contributing factor in the demise of the filament, evaporation is of greater concern. If the peak arc current can be maintained with less average heater current, the filament evaporation rate for this arc current will diminish. In the vacuum of an ion source, the authors expect the filaments to retain much of their heat throughout a 1 millisecond (12% duty) loss of heater current. A circuit to eliminate 100 ampere heater currents from filaments during the arc pulse was developed. The magnetic field due to the 100 ampere current tends to hold electrons to the filament, decreasing the arc current. By eliminating this magnetic field, the arc should be more efficient, allowing the filaments to run at a lower average heater current. This should extend the filament lifetime. The circuit development and preliminary filament results are discussed

  15. Copper-Based Aquatic Algaecide Adsorption and Accumulation Kinetics: Influence of Exposure Concentration and Duration for Controlling the Cyanobacterium Lyngbya wollei.

    Science.gov (United States)

    Bishop, West M; Lynch, Clayton L; Willis, Ben E; Cope, W Gregory

    2017-09-01

    Filamentous mat-forming cyanobacteria are increasingly impairing uses of freshwater resources. To effectively manage, a better understanding of control measures is needed. Copper (Cu)-based algaecide formulations are often applied to reactively control nuisance cyanobacterial blooms. This laboratory research assessed typical field exposure scenarios for the ability of Cu to partition to, and accumulate in Lyngbya wollei. Exposure factors (Cu concentration × duration) of 4, 8, 16, 24, 32 h were tested across three aqueous Cu concentrations (1, 2, 4 ppm). Results indicated that internally accumulated copper correlated with control of L. wollei, independent of adsorbed copper. L. wollei control was determined by filament viability and chlorophyll a concentrations. Similar exposure factors elicited similar internalized copper levels and consequent responses of L. wollei. Ultimately, a "concentration-exposure-time" (CET) model was created to assist water resource managers in selecting an appropriate treatment regime for a specific in-water infestation. By assessing the exposure concentration and duration required to achieve the internal threshold of copper (i.e., critical burden) that elicits control, water management objectives can be achieved while simultaneously decreasing the environmental loading of copper and potential for non-target species risks.

  16. Effect of solar radiation on photosynthesis and pigmentation in the cyanobacterium microcoleus chtihonoplastes

    International Nuclear Information System (INIS)

    Annan, J.N.; Galyuon, I. K. A.; Donkor, V.A.

    2007-01-01

    The effects of solar radiation on the photosynthetic oxygen production and pigmentation were investigated in the marine filamentous cyanobacterium. Microcoleus chthonoplastes harvested from the intertidal zone of the Biriwa coast in Ghana. The organism was exposed to unfiltered solar radiation (UV-B. UV-A and PAR) and solar radiation filtered through optical filters. WG320 (UV-A and PAR), GG400 (PAR only), and UG5 (only UV-B and UV-A), Photosynthetic oxygen production was impaired. The reduction in the rate of photosynthetic oxygen production took over 2 hours to occur. The photoinhibition due to unfiltered solar radiation and combined UV-A and PAR were most severe. Absorption spectra of the crude extracts of M. chthonoplastes, indicated the presence of chlorophyll a, carotenoids, phycoerythrin and phycocyanin as the photosynthetic pigments, which were significantly bleached under the various solar radiation wavelengths. Generally, the phycobilins were affected most. Fluorescence measurements showed peaks that decreased significantly in amplitude and also underwent a shift towards shorter wavelengths, with prolonged exposure time, indicating that energy transfer from the accessory pigments was adversely affected. The implication is that increased solar radiation may have severe consequences on the marine ecosystem. (au)

  17. Nostopeptolide plays a governing role during cellular differentiation of the symbiotic cyanobacterium Nostoc punctiforme.

    Science.gov (United States)

    Liaimer, Anton; Helfrich, Eric J N; Hinrichs, Katrin; Guljamow, Arthur; Ishida, Keishi; Hertweck, Christian; Dittmann, Elke

    2015-02-10

    Nostoc punctiforme is a versatile cyanobacterium that can live either independently or in symbiosis with plants from distinct taxa. Chemical cues from plants and N. punctiforme were shown to stimulate or repress, respectively, the differentiation of infectious motile filaments known as hormogonia. We have used a polyketide synthase mutant that accumulates an elevated amount of hormogonia as a tool to understand the effect of secondary metabolites on cellular differentiation of N. punctiforme. Applying MALDI imaging to illustrate the reprogramming of the secondary metabolome, nostopeptolides were identified as the predominant difference in the pks2(-) mutant secretome. Subsequent differentiation assays and visualization of cell-type-specific expression of nostopeptolides via a transcriptional reporter strain provided evidence for a multifaceted role of nostopeptolides, either as an autogenic hormogonium-repressing factor or as a chemoattractant, depending on its extracellular concentration. Although nostopeptolide is constitutively expressed in the free-living state, secreted levels dynamically change before, during, and after the hormogonium differentiation phase. The metabolite was found to be strictly down-regulated in symbiosis with Gunnera manicata and Blasia pusilla, whereas other metabolites are up-regulated, as demonstrated via MALDI imaging, suggesting plants modulate the fine-balanced cross-talk network of secondary metabolites within N. punctiforme.

  18. Novel toxic effects associated with a tropical Limnothrix/Geitlerinema-like cyanobacterium.

    Science.gov (United States)

    Bernard, Catherine; Froscio, Suzanne; Campbell, Rebecca; Monis, Paul; Humpage, Andrew; Fabbro, Larelle

    2011-06-01

    The presence of a toxic strain of a fine filamentous cyanobacterium belonging to the Oscillatorialean family Pseudanabaenacea was detected during a survey of cyanobacterial taxa associated with the presence of cylindrospermopsin in dams in Central Queensland (Australia). The strain, AC0243, was isolated and cultured, its genomic DNA extracted and 16S RNA gene sequenced. Phylogenetic analysis placed AC0243 with Limnothrix species, although this genus appears polyphyletic. Moreover, not all morphological characters are consistent with this genus but more closely fit the description of Geitlerinema unigranulatum (R.N. Singh) Komárek and Azevedo. The potential toxic effects of AC0243 extract were assessed chemically and biologically. Cell free protein synthesis was inhibited by the extract. Exposure of Vero cells to the extract resulted in a significant reduction in cellular ATP levels following 24-72 h incubation. The presence of cylindrospermopsin was excluded based on the nature of responses obtained in cell and cell-free assays; in addition, (i) it could not be detected by HPLC, LC-MS, or immunological assay, and (ii) no genes currently associated with the production of cylindrospermopsin were found in the genome. Other known cyanobacterial toxins were not detected. The apparent novelty of this toxin is discussed. Copyright © 2009 Wiley Periodicals, Inc.

  19. Proteome-wide analysis and diel proteomic profiling of the cyanobacterium Arthrospira platensis PCC 8005.

    Directory of Open Access Journals (Sweden)

    Sabine Matallana-Surget

    Full Text Available The filamentous cyanobacterium Arthrospira platensis has a long history of use as a food supply and it has been used by the European Space Agency in the MELiSSA project, an artificial microecosystem which supports life during long-term manned space missions. This study assesses progress in the field of cyanobacterial shotgun proteomics and light/dark diurnal cycles by focusing on Arthrospira platensis. Several fractionation workflows including gel-free and gel-based protein/peptide fractionation procedures were used and combined with LC-MS/MS analysis, enabling the overall identification of 1306 proteins, which represents 21% coverage of the theoretical proteome. A total of 30 proteins were found to be significantly differentially regulated under light/dark growth transition. Interestingly, most of the proteins showing differential abundance were related to photosynthesis, the Calvin cycle and translation processes. A novel aspect and major achievement of this work is the successful improvement of the cyanobacterial proteome coverage using a 3D LC-MS/MS approach, based on an immobilized metal affinity chromatography, a suitable tool that enabled us to eliminate the most abundant protein, the allophycocyanin. We also demonstrated that cell growth follows a light/dark cycle in A. platensis. This preliminary proteomic study has highlighted new characteristics of the Arthrospira platensis proteome in terms of diurnal regulation.

  20. Filament wound structure and method

    International Nuclear Information System (INIS)

    Dritt, W.S.; Gerth, H.L.; Knight, C.E. Jr.; Pardue, R.M.

    1977-01-01

    A filament wound spherical structure is described comprising a plurality of filament band sets disposed about the surface of a mandrel with each band of each set formed of a continuous filament circumferentially wound about the mandrel a selected number of circuits and with each circuit of filament being wound parallel to and contiguous with an immediate previously wound circuit. Each filament band in each band set is wound at the same helix angle from the axis of revolution of the mandrel and all of the bands of each set are uniformly distributed about the mandrel circumference. The pole-to-equator wall thickness taper associated with each band set, as several contiguous band sets are wound about the mandrel starting at the poles, is accumulative as the band sets are nested to provide a complete filament wound sphere of essentially uniform thickness

  1. Magnetic vortex filament flows

    International Nuclear Information System (INIS)

    Barros, Manuel; Cabrerizo, Jose L.; Fernandez, Manuel; Romero, Alfonso

    2007-01-01

    We exhibit a variational approach to study the magnetic flow associated with a Killing magnetic field in dimension 3. In this context, the solutions of the Lorentz force equation are viewed as Kirchhoff elastic rods and conversely. This provides an amazing connection between two apparently unrelated physical models and, in particular, it ties the classical elastic theory with the Hall effect. Then, these magnetic flows can be regarded as vortex filament flows within the localized induction approximation. The Hasimoto transformation can be used to see the magnetic trajectories as solutions of the cubic nonlinear Schroedinger equation showing the solitonic nature of those

  2. Soliton on thin vortex filament

    International Nuclear Information System (INIS)

    Konno, Kimiaki; Mituhashi, Masahiko; Ichikawa, Y.H.

    1990-12-01

    Showing that one of the equations found by Wadati, Konno and Ichikawa is equivalent to the equation of motion of a thin vortex filament, we investigate solitons on the vortex filament. N vortex soliton solution is given in terms of the inverse scattering method. We examine two soliton collision processes on the filament. Our analysis provides the theoretical foundation of two soliton collision processes observed numerically by Aref and Flinchem. (author)

  3. Solar Filament Extraction and Characterizing

    Science.gov (United States)

    Yuan, Yuan; Shih, F. Y.; Jing, J.; Wang, H.

    2010-05-01

    This paper presents a new method to extract and characterize solar filaments from H-alpha full-disk images produced by Big Bear Solar Observatory. A cascading Hough Transform method is designed to identify solar disk center location and radius. Solar disks are segmented from the background, and unbalanced illumination on the surface of solar disks is removed using polynomial surface fitting. And then a localized adaptive thresholding is employed to extract solar filament candidates. After the removal of small solar filament candidates, the remaining larger candidates are used as the seeds of region growing. The procedure of region growing not only connects broken filaments but also generate complete shape for each filament. Mathematical morphology thinning is adopted to produce the skeleton of each filament, and graph theory is used to prune branches and barbs to get the main skeleton. The length and the location of the main skeleton is characterized. The proposed method can help scientists and researches study the evolution of solar filament, for instance, to detect solar filament eruption. The presented method has already been used by Space Weather Research Lab of New Jersey Institute of Technology (http://swrl.njit.edu) to generate the solar filament online catalog using H-alpha full-disk images of Global H-alpha Network (http://swrl.njit.edu/ghn_web/).

  4. Culture temperature affects gene expression and metabolic pathways in the 2-methylisoborneol-producing cyanobacterium Pseudanabaena galeata.

    Science.gov (United States)

    Kakimoto, Masayuki; Ishikawa, Toshiki; Miyagi, Atsuko; Saito, Kazuaki; Miyazaki, Motonobu; Asaeda, Takashi; Yamaguchi, Masatoshi; Uchimiya, Hirofumi; Kawai-Yamada, Maki

    2014-02-15

    A volatile metabolite, 2-methylisoborneol (2-MIB), causes an unpleasant taste and odor in tap water. Some filamentous cyanobacteria produce 2-MIB via a two-step biosynthetic pathway: methylation of geranyl diphosphate (GPP) by methyl transferase (GPPMT), followed by the cyclization of methyl-GPP by monoterpene cyclase (MIBS). We isolated the genes encoding GPPMT and MIBS from Pseudanabaena galeata, a filamentous cyanobacterium known to be a major causal organism of 2-MIB production in Japanese lakes. The predicted amino acid sequence showed high similarity with that of Pseudanabaena limnetica (96% identity in GPPMT and 97% identity in MIBS). P. galeata was cultured at different temperatures to examine the effect of growth conditions on the production of 2-MIB and major metabolites. Gas chromatograph-mass spectrometry (GC-MS) measurements showed higher accumulation of 2-MIB at 30 °C than at 4 °C or 20 °C after 24 h of culture. Real-time-RT PCR analysis showed that the expression levels of the genes encoding GPPMT and MIBS decreased at 4 °C and increased at 30 °C, compared with at 20 °C. Furthermore, metabolite analysis showed dramatic changes in primary metabolite concentrations in cyanobacteria grown at different temperatures. The data indicate that changes in carbon flow in the TCA cycle affect 2-MIB biosynthesis at higher temperatures. Copyright © 2013 Elsevier GmbH. All rights reserved.

  5. Decoupling of ammonium regulation and ntcA transcription in the diazotrophic marine cyanobacterium Trichodesmium sp. IMS101.

    Science.gov (United States)

    Post, Anton F; Rihtman, Branko; Wang, Qingfeng

    2012-03-01

    Nitrogen (N) physiology in the marine cyanobacterium Trichodesmium IMS101 was studied along with transcript accumulation of the N-regulatory gene ntcA and of two of its target genes: napA (nitrate assimilation) and nifH (N(2) fixation). N(2) fixation was impaired in the presence of nitrite, nitrate and urea. Strain IMS101 was capable of growth on these combined N sources at ammonium. Whereas ecologically relevant N concentrations (2-20 μM) suppressed growth and assimilation, much higher concentrations were required to affect transcript levels. Transcripts of nifH accumulated under nitrogen-fixing conditions; these transcript levels were maintained in the presence of nitrate (100 μM) and ammonium (20 μM). However, nifH transcript levels were below detection at ammonium concentrations >20 μM. napA mRNA was found at low levels in both N(2)-fixing and ammonium-utilizing filaments, and it accumulated in filaments grown with nitrate. The positive effect of nitrate on napA transcription was abolished by ammonium additions of >200 μM. This effect was restored upon addition of the glutamine synthetase inhibitor L-methionin-DL-sulfoximine. Surprisingly, ntcA transcript levels remained high in the presence of ammonium, even at elevated concentrations. These findings indicate that ammonium repression is decoupled from transcriptional activation of ntcA in Trichodesmium IMS101.

  6. Amino Acid Transporters and Release of Hydrophobic Amino Acids in the Heterocyst-Forming Cyanobacterium Anabaena sp. Strain PCC 7120

    Directory of Open Access Journals (Sweden)

    Rafael Pernil

    2015-04-01

    Full Text Available Anabaena sp. strain PCC 7120 is a filamentous cyanobacterium that can use inorganic compounds such as nitrate or ammonium as nitrogen sources. In the absence of combined nitrogen, it can fix N2 in differentiated cells called heterocysts. Anabaena also shows substantial activities of amino acid uptake, and three ABC-type transporters for amino acids have been previously characterized. Seven new loci encoding predicted amino acid transporters were identified in the Anabaena genomic sequence and inactivated. Two of them were involved in amino acid uptake. Locus alr2535-alr2541 encodes the elements of a hydrophobic amino acid ABC-type transporter that is mainly involved in the uptake of glycine. ORF all0342 encodes a putative transporter from the dicarboxylate/amino acid:cation symporter (DAACS family whose inactivation resulted in an increased uptake of a broad range of amino acids. An assay to study amino acid release from Anabaena filaments to the external medium was set up. Net release of the alanine analogue α-aminoisobutyric acid (AIB was observed when transport system N-I (a hydrophobic amino acid ABC-type transporter was engaged in the uptake of a specific substrate. The rate of AIB release was directly proportional to the intracellular AIB concentration, suggesting leakage from the cells by diffusion.

  7. Colony formation in the cyanobacterium Microcystis.

    Science.gov (United States)

    Xiao, Man; Li, Ming; Reynolds, Colin S

    2018-02-22

    Morphological evolution from a unicellular to multicellular state provides greater opportunities for organisms to attain larger and more complex living forms. As the most common freshwater cyanobacterial genus, Microcystis is a unicellular microorganism, with high phenotypic plasticity, which forms colonies and blooms in lakes and reservoirs worldwide. We conducted a systematic review of field studies from the 1990s to 2017 where Microcystis was dominant. Microcystis was detected as the dominant genus in waterbodies from temperate to subtropical and tropical zones. Unicellular Microcystis spp. can be induced to form colonies by adjusting biotic and abiotic factors in laboratory. Colony formation by cell division has been induced by zooplankton filtrate, high Pb 2+ concentration, the presence of another cyanobacterium (Cylindrospermopsis raciborskii), heterotrophic bacteria, and by low temperature and light intensity. Colony formation by cell adhesion can be induced by zooplankton grazing, high Ca 2+ concentration, and microcystins. We hypothesise that single cells of all Microcystis morphospecies initially form colonies with a similar morphology to those found in the early spring. These colonies gradually change their morphology to that of M. ichthyoblabe, M. wesenbergii and M. aeruginosa with changing environmental conditions. Colony formation provides Microcystis with many ecological advantages, including adaption to varying light, sustained growth under poor nutrient supply, protection from chemical stressors and protection from grazing. These benefits represent passive tactics responding to environmental stress. Microcystis colonies form at the cost of decreased specific growth rates compared with a unicellular habit. Large colony size allows Microcystis to attain rapid floating velocities (maximum recorded for a single colony, ∼ 10.08 m h -1 ) that enable them to develop and maintain a large biomass near the surface of eutrophic lakes, where they may shade

  8. Photosynthetic Versatility in the Genome of Geitlerinema sp. PCC 9228 (Formerly Oscillatoria limnetica 'Solar Lake'), a Model Anoxygenic Photosynthetic Cyanobacterium.

    Science.gov (United States)

    Grim, Sharon L; Dick, Gregory J

    2016-01-01

    Anoxygenic cyanobacteria that use sulfide as the electron donor for photosynthesis are a potentially influential but poorly constrained force on Earth's biogeochemistry. Their versatile metabolism may have boosted primary production and nitrogen cycling in euxinic coastal margins in the Proterozoic. In addition, they represent a biological mechanism for limiting the accumulation of atmospheric oxygen, especially before the Great Oxidation Event and in the low-oxygen conditions of the Proterozoic. In this study, we describe the draft genome sequence of Geitlerinema sp. PCC 9228, formerly Oscillatoria limnetica 'Solar Lake', a mat-forming diazotrophic cyanobacterium that can switch between oxygenic photosynthesis and sulfide-based anoxygenic photosynthesis (AP). Geitlerinema possesses three variants of psbA , which encodes protein D1, a core component of the photosystem II reaction center. Phylogenetic analyses indicate that one variant is closely affiliated with cyanobacterial psbA genes that code for a D1 protein used for oxygen-sensitive processes. Another version is phylogenetically similar to cyanobacterial psbA genes that encode D1 proteins used under microaerobic conditions, and the third variant may be cued to high light and/or elevated oxygen concentrations. Geitlerinema has the canonical gene for sulfide quinone reductase (SQR) used in cyanobacterial AP and a putative transcriptional regulatory gene in the same operon. Another operon with a second, distinct sqr and regulatory gene is present, and is phylogenetically related to sqr genes used for high sulfide concentrations. The genome has a comprehensive nif gene suite for nitrogen fixation, supporting previous observations of nitrogenase activity. Geitlerinema possesses a bidirectional hydrogenase rather than the uptake hydrogenase typically used by cyanobacteria in diazotrophy. Overall, the genome sequence of Geitlerinema sp. PCC 9228 highlights potential cyanobacterial strategies to cope with fluctuating

  9. Genome Sequence and Composition of a Tolyporphin-Producing Cyanobacterium-Microbial Community.

    Science.gov (United States)

    Hughes, Rebecca-Ayme; Zhang, Yunlong; Zhang, Ran; Williams, Philip G; Lindsey, Jonathan S; Miller, Eric S

    2017-10-01

    The cyanobacterial culture HT-58-2 was originally described as a strain of Tolypothrix nodosa with the ability to produce tolyporphins, which comprise a family of distinct tetrapyrrole macrocycles with reported efflux pump inhibition properties. Upon reviving the culture from what was thought to be a nonextant collection, studies of culture conditions, strain characterization, phylogeny, and genomics have been undertaken. Here, HT-58-2 was shown by 16S rRNA analysis to closely align with Brasilonema strains and not with Tolypothrix isolates. Light, fluorescence, and scanning electron microscopy revealed cyanobacterium filaments that are decorated with attached bacteria and associated with free bacteria. Metagenomic surveys of HT-58-2 cultures revealed a diversity of bacteria dominated by Erythrobacteraceae , 97% of which are Porphyrobacter species. A dimethyl sulfoxide washing procedure was found to yield enriched cyanobacterial DNA (presumably by removing community bacteria) and sequence data sufficient for genome assembly. The finished, closed HT-58-2Cyano genome consists of 7.85 Mbp (42.6% G+C) and contains 6,581 genes. All genes for biosynthesis of tetrapyrroles (e.g., heme, chlorophyll a , and phycocyanobilin) and almost all for cobalamin were identified dispersed throughout the chromosome. Among the 6,177 protein-encoding genes, coding sequences (CDSs) for all but two of the eight enzymes for conversion of glutamic acid to protoporphyrinogen IX also were found within one major gene cluster. The cluster also includes 10 putative genes (and one hypothetical gene) encoding proteins with domains for a glycosyltransferase, two cytochrome P450 enzymes, and a flavin adenine dinucleotide (FAD)-binding protein. The composition of the gene cluster suggests a possible role in tolyporphin biosynthesis. IMPORTANCE A worldwide search more than 25 years ago for cyanobacterial natural products with anticancer activity identified a culture (HT-58-2) from Micronesia that

  10. Modern filaments for composite materials

    International Nuclear Information System (INIS)

    Krivelli-Viskonti, I.

    1982-01-01

    Analysis of modern state and ways to improve properties of different filaments for the forecast of the filament application in composite materials has been conducted. In the near future as before the greatest attention will be paid to fibre glass, as this material is widely used in the reinforcing of organic matrices. Carbon and kevlar filaments are the most prospective ones. For the service at medium, high or superhigh temperatures selection of matrix material is more significant than selection of filament. Organic matrices can not be used at temperatures > 250 deg C: this is already the range of metal matrix application. Though at temperatures above room one many filaments can be used, boron filaments and metal wire are the only reinforcing materials, inspite of the fact that carbon filaments are successfully used for metal matrix reinforcing. At very high temperatures only carbon filaments or silicon carbide ones can be used, but their cost is very high and besides economical problems there are many difficulties of technical character

  11. Filaments and clusters of galaxies

    International Nuclear Information System (INIS)

    Soltan, A.

    1987-01-01

    A statistical test to investigate filaments of galaxies is performed. Only particular form of filaments is considered, viz. filaments connecting Abell clusters of galaxies. Relative position of triplets ''cluster - field object - cluster'' is analysed. Though neither cluster sample nor field object sample are homogeneous and complete only peculiar form of selection effects could affect the present statistics. Comparison of observational data with simulations shows that less than 15 per cent of all field galaxies is concentrated in filaments connecting rich clusters. Most of the field objects used in the analysis are not normal galaxies and it is possible that this conclusion is not in conflict with apparent filaments seen in the Lick counts and in some nearby 3D maps of the galaxy distribution. 26 refs., 2 figs. (author)

  12. The Cyanobacterium Cylindrospermopsis raciborskii (CYRF-01 Responds to Environmental Stresses with Increased Vesiculation Detected at Single-Cell Resolution

    Directory of Open Access Journals (Sweden)

    Victor Zarantonello

    2018-02-01

    Full Text Available Secretion of membrane-limited vesicles, collectively termed extracellular vesicles (EVs, is an important biological process of both eukaryotic and prokaryotic cells. This process has been observed in bacteria, but remains to be better characterized at high resolution in cyanobacteria. In the present work, we address the release of EVs by Cylindrospermopsis raciborskii (CYRF-01, a filamentous bloom-forming cyanobacterium, exposed to environmental stressors. First, non-axenic cultures of C. raciborskii (CYRF-01 were exposed to ultraviolet radiation (UVA + UVB over a 6 h period, which is known to induce structural damage to this species. Second, C. raciborskii was co-cultured in interaction with another cyanobacterium species, Microcystis aeruginosa (MIRF-01, over a 24 h period. After the incubation times, cell density and viability were analyzed, and samples were processed for transmission electron microscopy (TEM. Our ultrastructural analyses revealed that C. raciborskii constitutively releases EVs from the outer membrane during its normal growth and amplifies such ability in response to environmental stressors. Both situations induced significant formation of outer membrane vesicles (OMVs by C. raciborskii compared to control cells. Quantitative TEM revealed an increase of 48% (UV and 60% (interaction in the OMV numbers compared to control groups. Considering all groups, the OMVs ranged in size from 20 to 300 nm in diameter, with most OMVs showing diameters between 20 and 140 nm. Additionally, we detected that OMV formation is accompanied by phosphatidylserine exposure, a molecular event also observed in EV-secreting eukaryotic cells. Altogether, we identified for the first time that C. raciborskii has the competence to secrete OMVs and that under different stress situations the genesis of these vesicles is increased. The amplified ability of cyanobacteria to release OMVs may be associated with adaptive responses to changes in environmental

  13. Molecular exploration of the highly radiation resistant cyanobacterium Arthrospira sp. PCC 8005

    Science.gov (United States)

    Badri, Hanène; Leys, Natalie; Wattiez, Ruddy

    Arthrospira (Spirulina) is a photosynthetic cyanobacterium able to use sunlight to release oxygen from water and remove carbon dioxide and nitrate from water. In addition, it is suited for human consumption (edible). For these traits, the cyanobacterium Arthrospira sp. PCC 8005 was selected by the European Space Agency (ESA) as part of the life support system MELiSSA for recycling oxygen, water, and food during future long-haul space missions. However, during such extended missions, Arthrospira sp. PCC 8005 will be exposed to continuous artificial illumination and harmful cosmic radiation. The aim of this study was to investigate how Arthrospira will react and behave when exposed to such stress environment. The cyanobacterium Arthrospira sp. PCC 8005 was exposed to high gamma rays doses in order to unravel in details the response of this bacterium following such stress. Test results showed that after acute exposure to high doses of 60Co gamma radiation upto 3200 Gy, Arthrospira filaments were still able to restart photosynthesis and proliferate normally. Doses above 3200 Gy, did have a detrimental effect on the cells, and delayed post-irradiation proliferation. The photosystem activity, measured as the PSII quantum yield immediately after irradiation, decreased significantly at radiation doses above 3200 Gy. Likewise through pigment content analysis a significant decrease in phycocyanin was observed following exposure to 3200 Gy. The high tolerance of this bacterium to 60Co gamma rays (i.e. ca. 1000x more resistant than human cells for example) raised our interest to investigate in details the cellular and molecular mechanisms behind this amazing resistance. Optimised DNA, RNA and protein extraction methods and a new microarray chip specific for Arthrospira sp. PCC 8005 were developed to identify the global cellular and molecular response following exposure to 3200 Gy and 5000 Gy A total of 15,29 % and 30,18 % genes were found differentially expressed in RNA

  14. Effects of UV-B Radiation and Periodic Desiccation on the Morphogenesis of the Edible Terrestrial Cyanobacterium Nostoc flagelliforme

    Science.gov (United States)

    Feng, Yan-Na; Zhang, Zhong-Chun; Feng, Jun-Li

    2012-01-01

    The terrestrial cyanobacterium Nostoc flagelliforme Berk. et M. A. Curtis has been a popular food and herbal ingredient for hundreds of years. To meet great market demand and protect the local ecosystem, for decades researchers have tried to cultivate N. flagelliforme but have failed to get macroscopic filamentous thalli. In this study, single trichomes with 50 to 200 vegetative cells were induced from free-living cells by low light and used to investigate the morphogenesis of N. flagelliforme under low UV-B radiation and periodic desiccation. Low-fluence-rate UV-B (0.1 W m−2) did not inhibit trichome growth; however, it significantly increased the synthesis of extracellular polysaccharides and mycosporine-like amino acids and promoted sheath formation outside the trichomes. Under low UV-B radiation, single trichomes developed into filamentous thalli more than 1 cm long after 28 days of cultivation, most of which grew separately in liquid BG11 medium. With periodic desiccation treatment, the single trichomes formed flat or banded thalli that grew up to 2 cm long after 3 months on solid BG11 medium. When trichomes were cultivated on solid BG11 medium with alternate treatments of low UV-B and periodic desiccation, dark and scraggly filamentous thalli that grew up to about 3 cm in length after 40 days were obtained. In addition, the cultivation of trichomes on nitrogen-deficient solid BG11 medium (BG110) suggested that nitrogen availability could affect the color and lubricity of newly developed thalli. This study provides promising techniques for artificial cultivation of N. flagelliforme in the future. PMID:22865081

  15. Antitumor activity of hierridin B, a cyanobacterial secondary metabolite found in both filamentous and unicellular marine strains.

    Directory of Open Access Journals (Sweden)

    Pedro N Leão

    Full Text Available Cyanobacteria are widely recognized as a valuable source of bioactive metabolites. The majority of such compounds have been isolated from so-called complex cyanobacteria, such as filamentous or colonial forms, which usually display a larger number of biosynthetic gene clusters in their genomes, when compared to free-living unicellular forms. Nevertheless, picocyanobacteria are also known to have potential to produce bioactive natural products. Here, we report the isolation of hierridin B from the marine picocyanobacterium Cyanobium sp. LEGE 06113. This compound had previously been isolated from the filamentous epiphytic cyanobacterium Phormidium ectocarpi SAG 60.90, and had been shown to possess antiplasmodial activity. A phylogenetic analysis of the 16S rRNA gene from both strains confirmed that these cyanobacteria derive from different evolutionary lineages. We further investigated the biological activity of hierridin B, and tested its cytotoxicity towards a panel of human cancer cell lines; it showed selective cytotoxicity towards HT-29 colon adenocarcinoma cells.

  16. A high constitutive catalase activity confers resistance to methyl viologen-promoted oxidative stress in a mutant of the cyanobacterium Nostoc punctiforme ATCC 29133.

    Science.gov (United States)

    Moirangthem, Lakshmipyari Devi; Bhattacharya, Sudeshna; Stensjö, Karin; Lindblad, Peter; Bhattacharya, Jyotirmoy

    2014-04-01

    A spontaneous methyl viologen (MV)-resistant mutant of the nitrogen-fixing cyanobacterium Nostoc punctiforme ATCC 29133 was isolated and the major enzymatic antioxidants involved in combating MV-induced oxidative stress were evaluated. The mutant displayed a high constitutive catalase activity as a consequence of which, the intracellular level of reactive oxygen species in the mutant was lower than the wild type (N. punctiforme) in the presence of MV. The superoxide dismutase (SOD) activity that consisted of a SodA (manganese-SOD) and a SodB (iron-SOD) was not suppressed in the mutant following MV treatment. The mutant was, however, characterised by a lower peroxidase activity compared with its wild type, and its improved tolerance to externally added H₂O₂ could only be attributed to enhanced catalase activity. Furthermore, MV-induced toxic effects on the wild type such as (1) loss of photosynthetic performance assessed as maximal quantum yield of photosystem II, (2) nitrogenase inactivation, and (3) filament fragmentation and cell lysis were not observed in the mutant. These findings highlight the importance of catalase in preventing MV-promoted oxidative damage and cell death in the cyanobacterium N. punctiforme. Such oxidative stress resistant mutants of cyanobacteria are likely to be a better source of biofertilisers, as they can grow and fix nitrogen in an unhindered manner in agricultural fields that are often contaminated with the herbicide MV, also commonly known as paraquat.

  17. Antagonism at combined effects of chemical fertilizers and carbamate insecticides on the rice-field N2-fixing cyanobacterium Cylindrospermum sp. in vitro

    Directory of Open Access Journals (Sweden)

    Padhy Rabindra N.

    2014-03-01

    Full Text Available Effects of chemical fertilizers (urea, super phosphate and potash on toxicities of two carbamate insecticides, carbaryl and carbofuran, individually to the N2-fixing cyanobacterium, Cylindrospermum sp. were studied in vitro at partially lethal levels (below highest permissive concentrations of each insecticide. The average number of vegetative cells between two polar heterocysts was 16.3 in control cultures, while the mean value of filament length increased in the presence of chemical fertilizers, individually. Urea at the 10 ppm level was growth stimulatory and at the 50 ppm level it was growth inhibitory in control cultures, while at 100 ppm it was antagonistic, i.e. toxicity-enhancing along with carbaryl, individually to the cyanobacterium, antagonism was recorded. Urea at 50 ppm had toxicity reducing effect with carbaryl or carbofuran. At 100 and 250 ppm carbofuran levels, 50 ppm urea only had a progressive growth enhancing effect, which was marked well at 250 ppm carbofuran level, a situation of synergism. Super phosphate at the 10 ppm level only was growth promoting in control cultures, but it was antagonistic at its higher levels (50 and 100 ppm along with both insecticides, individually. Potash (100, 200, 300 and 400 ppm reduced toxicity due to carbaryl 20 and carbofuran 250 ppm levels, but potash was antagonistic at the other insecticide levels. The data clearly showed that the chemical fertilizers used were antagonistic with both the insecticides during toxicity to Cylindrospermum sp.

  18. Antagonism at combined effects of chemical fertilizers and carbamate insecticides on the rice-field N2-fixing cyanobacterium Cylindrospermum sp. in vitro

    Science.gov (United States)

    Nayak, Nabakishore; Rath, Shakti

    2014-01-01

    Effects of chemical fertilizers (urea, super phosphate and potash) on toxicities of two carbamate insecticides, carbaryl and carbofuran, individually to the N2-fixing cyanobacterium, Cylindrospermum sp. were studied in vitro at partially lethal levels (below highest permissive concentrations) of each insecticide. The average number of vegetative cells between two polar heterocysts was 16.3 in control cultures, while the mean value of filament length increased in the presence of chemical fertilizers, individually. Urea at the 10 ppm level was growth stimulatory and at the 50 ppm level it was growth inhibitory in control cultures, while at 100 ppm it was antagonistic, i.e. toxicity-enhancing along with carbaryl, individually to the cyanobacterium, antagonism was recorded. Urea at 50 ppm had toxicity reducing effect with carbaryl or carbofuran. At 100 and 250 ppm carbofuran levels, 50 ppm urea only had a progressive growth enhancing effect, which was marked well at 250 ppm carbofuran level, a situation of synergism. Super phosphate at the 10 ppm level only was growth promoting in control cultures, but it was antagonistic at its higher levels (50 and 100 ppm) along with both insecticides, individually. Potash (100, 200, 300 and 400 ppm) reduced toxicity due to carbaryl 20 and carbofuran 250 ppm levels, but potash was antagonistic at the other insecticide levels. The data clearly showed that the chemical fertilizers used were antagonistic with both the insecticides during toxicity to Cylindrospermum sp. PMID:26038669

  19. Hopanoids play a role in stress tolerance and nutrient storage in the cyanobacterium Nostoc punctiforme.

    Science.gov (United States)

    Ricci, J N; Morton, R; Kulkarni, G; Summers, M L; Newman, D K

    2017-01-01

    Hopanes are abundant in ancient sedimentary rocks at discrete intervals in Earth history, yet interpreting their significance in the geologic record is complicated by our incomplete knowledge of what their progenitors, hopanoids, do in modern cells. To date, few studies have addressed the breadth of diversity of physiological functions of these lipids and whether those functions are conserved across the hopanoid-producing bacterial phyla. Here, we generated mutants in the filamentous cyanobacterium, Nostoc punctiforme, that are unable to make all hopanoids (shc) or 2-methylhopanoids (hpnP). While the absence of hopanoids impedes growth of vegetative cells at high temperature, the shc mutant grows faster at low temperature. This finding is consistent with hopanoids acting as membrane rigidifiers, a function shared by other hopanoid-producing phyla. Apart from impacting fitness under temperature stress, hopanoids are dispensable for vegetative cells under other stress conditions. However, hopanoids are required for stress tolerance in akinetes, a resting survival cell type. While 2-methylated hopanoids do not appear to contribute to any stress phenotype, total hopanoids and to a lesser extent 2-methylhopanoids were found to promote the formation of cyanophycin granules in akinetes. Finally, although hopanoids support symbiotic interactions between Alphaproteobacteria and plants, they do not appear to facilitate symbiosis between N. punctiforme and the hornwort Anthoceros punctatus. Collectively, these findings support interpreting hopanes as general environmental stress biomarkers. If hopanoid-mediated enhancement of nitrogen-rich storage products turns out to be a conserved phenomenon in other organisms, a better understanding of this relationship may help us parse the enrichment of 2-methylhopanes in the rock record during episodes of disrupted nutrient cycling. © 2016 John Wiley & Sons Ltd.

  20. Isolation and characterization of the small subunit of the uptake hydrogenase from the cyanobacterium Nostoc punctiforme.

    Science.gov (United States)

    Raleiras, Patrícia; Kellers, Petra; Lindblad, Peter; Styring, Stenbjörn; Magnuson, Ann

    2013-06-21

    In nitrogen-fixing cyanobacteria, hydrogen evolution is associated with hydrogenases and nitrogenase, making these enzymes interesting targets for genetic engineering aimed at increased hydrogen production. Nostoc punctiforme ATCC 29133 is a filamentous cyanobacterium that expresses the uptake hydrogenase HupSL in heterocysts under nitrogen-fixing conditions. Little is known about the structural and biophysical properties of HupSL. The small subunit, HupS, has been postulated to contain three iron-sulfur clusters, but the details regarding their nature have been unclear due to unusual cluster binding motifs in the amino acid sequence. We now report the cloning and heterologous expression of Nostoc punctiforme HupS as a fusion protein, f-HupS. We have characterized the anaerobically purified protein by UV-visible and EPR spectroscopies. Our results show that f-HupS contains three iron-sulfur clusters. UV-visible absorption of f-HupS has bands ∼340 and 420 nm, typical for iron-sulfur clusters. The EPR spectrum of the oxidized f-HupS shows a narrow g = 2.023 resonance, characteristic of a low-spin (S = ½) [3Fe-4S] cluster. The reduced f-HupS presents complex EPR spectra with overlapping resonances centered on g = 1.94, g = 1.91, and g = 1.88, typical of low-spin (S = ½) [4Fe-4S] clusters. Analysis of the spectroscopic data allowed us to distinguish between two species attributable to two distinct [4Fe-4S] clusters, in addition to the [3Fe-4S] cluster. This indicates that f-HupS binds [4Fe-4S] clusters despite the presence of unusual coordinating amino acids. Furthermore, our expression and purification of what seems to be an intact HupS protein allows future studies on the significance of ligand nature on redox properties of the iron-sulfur clusters of HupS.

  1. DL-7-azatryptophan and citrulline metabolism in the cyanobacterium Anabaena sp. strain 1F

    International Nuclear Information System (INIS)

    Chen, C.H.; Van Baalen, C.; Tabita, F.R.

    1987-01-01

    An alternative route for the primary assimilation of ammonia proceeds via glutamine synthetase-carbamyl phosphate synthetase and its inherent glutaminase activity in Anabaena sp. strain 1F, a marine filamentous, heterocystous cyanobacterium. Evidence for the presence of this possible alternative route to glutamate was provided by the use of amino acid analogs as specific enzyme inhibitors, enzymological studies, and radioistopic labeling experiments. The amino acid pool patterns of continuous cultures of Anabaena sp. strain 1F were markedly influenced by the nitrogen source. A relatively high concentration of glutamate was maintained in the amino acid pools of all cultures irrespective of the nitrogen source, reflecting the central role of glutamate in nitrogen metabolism. The addition of 1.0 microM azaserine increased the intracellular pools of glutamate and glutamine. All attempts to detect any enzymatic activity for glutamate synthase by measuring the formation of L-[ 14 C]glutamate from 2-keto-[1- 14 C]glutarate and glutamine failed. The addition of 10 microM DL-7-azatryptophan caused a transient accumulation of intracellular citrulline and alanine which was not affected by the presence of chloramphenicol. The in vitro activity of carbamyl phosphate synthetase and glutaminase increased severalfold in the presence of azatryptophan. Results from radioisotopic labeling experiments with [ 14 C]bicarbonate and L-[1- 14 C]ornithine also indicated that citrulline was formed via carbamyl phosphate synthetase and ornithine transcarbamylase. In addition to its effects on nitrogen metabolism, azatryptophan also affected carbon metabolism by inhibiting photosynthetic carbon assimilation and photosynthetic oxygen evolution

  2. Composition and functional property of photosynthetic pigments under circadian rhythm in the cyanobacterium Spirulina platensis.

    Science.gov (United States)

    Kumar, Deepak; Kannaujiya, Vinod K; Richa; Pathak, Jainendra; Sundaram, Shanthy; Sinha, Rajeshwar P

    2018-05-01

    Circadian rhythm is an important endogenous biological signal for sustainable growth and development of cyanobacteria in natural ecosystems. Circadian effects of photosynthetically active radiation (PAR), ultraviolet-A (UV-A) and ultraviolet-B (UV-B) radiations on pigment composition have been studied in the cyanobacterium Spirulina platensis under light (L)/dark (D) oscillation with a combination of 4/20, 8/16, 12/12, 16/8, 20/4 and 24/24 h time duration. Circadian exposure of PAR + UV-A (PA) and PAR + UV-A + UV-B (PAB) showed more than twofold decline in Chl a, total protein and phycocyanin (PC) in light phase and significant recovery was achieved in dark phase. The fluorescence emission wavelength of PC was shifted towards lower wavelengths in the light phase of PAB in comparison to P and PA whereas the same wavelength was retrieved in the dark phase. The production of free radicals was accelerated twofold in the light phase (24 h L) whereas the same was retrieved to the level of control during the dark phase. Oxidatively induced damage was alleviated by antioxidative enzymes such as catalase (CAT), peroxidase (POD), superoxide dismutase (SOD) and ascorbate peroxidase (APX) in the light phase (0-24-h L) whereas the dark phase showed significant inhibition of the same enzymes. Similar characteristic inhibition of free radicals and recovery of PC was observed inside cellular filament after circadian rhythm of 24/24 h (L/D). Circadian exposure of P, PA and PAB significantly altered the synthesis and recovery of pigments that could be crucial for optimization and sustainable production of photosynthetic products for human welfare.

  3. Stability of two-dimensional vorticity filaments

    International Nuclear Information System (INIS)

    Elhmaidi, D.; Provenzale, A.; Lili, T.; Babiano, A.

    2004-01-01

    We discuss the results of a numerical study on the stability of two-dimensional vorticity filaments around a circular vortex. We illustrate how the stability of the filaments depends on the balance between the strain associated with the far field of the vortex and the local vorticity of the filament, and we discuss an empirical criterion for filament stability

  4. Boolean gates on actin filaments

    International Nuclear Information System (INIS)

    Siccardi, Stefano; Tuszynski, Jack A.; Adamatzky, Andrew

    2016-01-01

    Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications. - Highlights: • We simulate interaction between voltage pulses using on actin filaments. • We use a coupled nonlinear transmission line model. • We design Boolean logical gates via interactions between the voltage pulses. • We construct one-bit half-adder with interacting voltage pulses.

  5. Boolean gates on actin filaments

    Energy Technology Data Exchange (ETDEWEB)

    Siccardi, Stefano, E-mail: ssiccardi@2ssas.it [The Unconventional Computing Centre, University of the West of England, Bristol (United Kingdom); Tuszynski, Jack A., E-mail: jackt@ualberta.ca [Department of Oncology, University of Alberta, Edmonton, Alberta (Canada); Adamatzky, Andrew, E-mail: andrew.adamatzky@uwe.ac.uk [The Unconventional Computing Centre, University of the West of England, Bristol (United Kingdom)

    2016-01-08

    Actin is a globular protein which forms long polar filaments in the eukaryotic cytoskeleton. Actin networks play a key role in cell mechanics and cell motility. They have also been implicated in information transmission and processing, memory and learning in neuronal cells. The actin filaments have been shown to support propagation of voltage pulses. Here we apply a coupled nonlinear transmission line model of actin filaments to study interactions between voltage pulses. To represent digital information we assign a logical TRUTH value to the presence of a voltage pulse in a given location of the actin filament, and FALSE to the pulse's absence, so that information flows along the filament with pulse transmission. When two pulses, representing Boolean values of input variables, interact, then they can facilitate or inhibit further propagation of each other. We explore this phenomenon to construct Boolean logical gates and a one-bit half-adder with interacting voltage pulses. We discuss implications of these findings on cellular process and technological applications. - Highlights: • We simulate interaction between voltage pulses using on actin filaments. • We use a coupled nonlinear transmission line model. • We design Boolean logical gates via interactions between the voltage pulses. • We construct one-bit half-adder with interacting voltage pulses.

  6. Electron emitting filaments for electron discharge devices

    International Nuclear Information System (INIS)

    Leung, K.N.; Pincosy, P.A.; Ehlers, K.W.

    1988-01-01

    This patent describes an electron emitting device for use in an electron discharge system. It comprises: a filament having a pair of terminal ends, electrical supply means for supplying electrical power to the terminal ends of the filament for directly heating the filament by the passage of an electrical current along the filament between the terminal ends, the filament being substantially tapered in cross section continuously in one direction from one of its pair of terminal ends to another of its pair of terminal ends to achieve uniform heating of the filament along the length thereof by compensating for the nonuniform current along the filament due to the emission of electrons therefrom

  7. Three New Malyngamides from the Marine Cyanobacterium Moorea producens

    Directory of Open Access Journals (Sweden)

    Kosuke Sueyoshi

    2017-11-01

    Full Text Available Three new compounds of the malyngamide series, 6,8-di-O-acetylmalyngamide 2 (1, 6-O-acetylmalyngamide 2 (2, and N-demethyl-isomalyngamide I (3, were isolated from the marine cyanobacterium Moorea producens. Their structures were determined by spectroscopic analysis and chemical derivatization and degradation. These compounds stimulated glucose uptake in cultured L6 myotubes. In particular, 6,8-di-O-acetylmalyngamide 2 (1 showed potent activity and activated adenosine monophosphate-activated protein kinase (AMPK.

  8. Isolation, characterization and localization of extracellular polymeric substances from the cyanobacterium Arthrospira platensis strain MMG-9

    NARCIS (Netherlands)

    Ahmed, M.; Moerdijk-Poortvliet, T.C.W.; Wijnholds, A.; Stal, L.J.; Hasnain, S.

    2014-01-01

    Arthrospira platensis is a cyanobacterium known for its nutritional value and secondary metabolites. Extracellular polymeric substances (EPS) are an important trait of most cyanobacteria, including A. platensis. Here, we extracted and analysed different fractions of EPS from a locally isolated

  9. Isolation, characterization and localization of extracellular polymeric substances from the cyanobacterium

    NARCIS (Netherlands)

    Ahmed, M.; Wijnholds, A.; Stal, L.J.; Hasnain, S.

    2014-01-01

    Arthrospira platensis is a cyanobacterium known for its nutritional value and secondary metabolites. Extracellular polymeric substances (EPS) are an important trait of most cyanobacteria, including A. platensis. Here, we extracted and analysed different fractions of EPS from a locally isolated

  10. Moessbauer study of cobalt and iron in the cyanobacterium (blue green alga)

    International Nuclear Information System (INIS)

    Ambe, Shizuko

    1990-01-01

    Moessbauer emission and absorption studies have been performed on cobalt and iron in the cyanobacterium (blue-green alga). The Moessbauer spectrum of the cyanobacterium cultivated with 57 Co is decomposed into two doublets. The parameters of the major doublet are in good agreement with those of cyanocobalamin (vitamin B 12 ) labeled with 57 Co. The other minor doublet has parameters close to those of Fe(II) coordinated with six nitrogen atoms. These suggest that cobalt is used for the biosynthesis of vitamin B 12 or its analogs in the cyanobacterium. The spectra of the cyanobacterium grown with 57 Fe show that iron is in the high-spin trivalent state and possibly in the form of ferritin, iron storage protein. (orig.)

  11. Identification of genes implicated in toxin production in the cyanobacterium Cylindrospermopsis raciborskii

    DEFF Research Database (Denmark)

    Schembri, Mark; Neilan, B.A.; Saint, C.P.

    2001-01-01

    Cylindrospermopsis raciborskii is a bloom-forming cyanobacterium found in both tropical and temperate climates which produces cylindrospermopsin, a potent hepatotoxic secondary metabolite. This organism is notorious for its association with a significant human poisoning incident on Palm Island...

  12. Magnetic helicity and active filament configuration

    Science.gov (United States)

    Romano, P.; Zuccarello, F.; Poedts, S.; Soenen, A.; Zuccarello, F. P.

    2009-11-01

    Context: The role of magnetic helicity in active filament formation and destabilization is still under debate. Aims: Although active filaments usually show a sigmoid shape and a twisted configuration before and during their eruption, it is unclear which mechanism leads to these topologies. In order to provide an observational contribution to clarify these issues, we describe a filament evolution whose characteristics seem to be directly linked to the magnetic helicity transport in corona. Methods: We applied different methods to determine the helicity sign and the chirality of the filament magnetic field. We also computed the magnetic helicity transport rate at the filament footpoints. Results: All the observational signatures provided information on the positive helicity and sinistral chirality of the flux rope containing the filament material: its forward S shape, the orientation of its barbs, the bright and dark threads at 195 Å. Moreover, the magnetic helicity transport rate at the filament footpoints showed a clear accumulation of positive helicity. Conclusions: The study of this event showed a correspondence between several signatures of the sinistral chirality of the filament and several evidences of the positive magnetic helicity of the filament magnetic field. We also found that the magnetic helicity transported along the filament footpoints showed an increase just before the change of the filament shape observed in Hα images. We argued that the photospheric regions where the filament was rooted might be the preferential ways where the magnetic helicity was injected along the filament itself and where the conditions to trigger the eruption were yielded.

  13. Genome Sequence and Composition of a Tolyporphin-Producing Cyanobacterium-Microbial Community

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Rebecca-Ayme; Zhang, Yunlong; Zhang, Ran; Williams, Philip G.; Lindsey, Jonathan S.; Miller, Eric S.; Nojiri, Hideaki

    2017-07-28

    ABSTRACT

    The cyanobacterial culture HT-58-2 was originally described as a strain ofTolypothrix nodosawith the ability to produce tolyporphins, which comprise a family of distinct tetrapyrrole macrocycles with reported efflux pump inhibition properties. Upon reviving the culture from what was thought to be a nonextant collection, studies of culture conditions, strain characterization, phylogeny, and genomics have been undertaken. Here, HT-58-2 was shown by 16S rRNA analysis to closely align withBrasilonemastrains and not withTolypothrixisolates. Light, fluorescence, and scanning electron microscopy revealed cyanobacterium filaments that are decorated with attached bacteria and associated with free bacteria. Metagenomic surveys of HT-58-2 cultures revealed a diversity of bacteria dominated byErythrobacteraceae, 97% of which arePorphyrobacterspecies. A dimethyl sulfoxide washing procedure was found to yield enriched cyanobacterial DNA (presumably by removing community bacteria) and sequence data sufficient for genome assembly. The finished, closed HT-58-2Cyano genome consists of 7.85 Mbp (42.6% G+C) and contains 6,581 genes. All genes for biosynthesis of tetrapyrroles (e.g., heme, chlorophylla, and phycocyanobilin) and almost all for cobalamin were identified dispersed throughout the chromosome. Among the 6,177 protein-encoding genes, coding sequences (CDSs) for all but two of the eight enzymes for conversion of glutamic acid to protoporphyrinogen IX also were found within one major gene cluster. The cluster also includes 10 putative genes (and one hypothetical gene) encoding proteins with

  14. Various Barbs in Solar Filaments

    Science.gov (United States)

    Filippov, Boris

    2017-07-01

    Interest to lateral details of the solar filament shape named barbs, motivated by their relationship to filament chirality and helicity, showed their different orientation relative to the expected direction of the magnetic field. While the majority of barbs are stretched along the field, some barbs seem to be transversal to it and are referred to as anomalous barbs. We analyse the deformation of helical field lines by a small parasitic polarity using a simple flux rope model with a force-free field. A rather small and distant source of parasitic polarity stretches the bottom parts of the helical lines in its direction creating a lateral extension of dips below the flux-rope axis. They can be considered as normal barbs of the filament. A stronger and closer source of parasitic polarity makes the flux-rope field lines to be convex below its axis and creates narrow and deep dips near its position. As a result, the narrow structure, with thin threads across it, is formed whose axis is nearly perpendicular to the field. The structure resembles an anomalous barb. Hence, the presence of anomalous barbs does not contradict the flux-rope structure of a filament.

  15. Star-forming Filament Models

    International Nuclear Information System (INIS)

    Myers, Philip C.

    2017-01-01

    New models of star-forming filamentary clouds are presented in order to quantify their properties and to predict their evolution. These 2D axisymmetric models describe filaments that have no core, one low-mass core, and one cluster-forming core. They are based on Plummer-like cylinders and spheroids that are bounded by a constant-density surface of finite extent. In contrast to 1D Plummer-like models, they have specific values of length and mass, they approximate observed column density maps, and their distributions of column density ( N -pdfs) are pole-free. Each model can estimate the star-forming potential of a core-filament system by identifying the zone of gas dense enough to form low-mass stars and by counting the number of enclosed thermal Jeans masses. This analysis suggests that the Musca central filament may be near the start of its star-forming life, with enough dense gas to make its first ∼3 protostars, while the Coronet filament is near the midpoint of its star formation, with enough dense gas to add ∼8 protostars to its ∼20 known stars. In contrast, L43 appears to be near the end of its star-forming life, since it lacks enough dense gas to add any new protostars to the two young stellar objectsalready known.

  16. Capillary thinning of polymeric filaments

    DEFF Research Database (Denmark)

    Kolte, Mette Irene; Szabo, Peter

    1999-01-01

    The capillary thinning of filaments of a Newtonian polybutene fluid and a viscoelastic polyisobutylene solution are analyzed experimentally and by means of numerical simulation. The experimental procedure is as follows. Initially, a liquid sample is placed between two cylindrical plates. Then, th...

  17. Transient filament stretching rheometer II

    DEFF Research Database (Denmark)

    Kolte, Mette Irene; Rasmussen, Henrik K.; Hassager, Ole

    1997-01-01

    The Lagrangian sspecification is used to simulate the transient stretching filament rheometer. Simulations are performed for dilute PIB-solutions modeled as a four mode Oldroyd-B fluid and a semidilute PIB-solution modeled as a non-linear single integral equation. The simulations are compared...

  18. Star-forming Filament Models

    Energy Technology Data Exchange (ETDEWEB)

    Myers, Philip C., E-mail: pmyers@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)

    2017-03-20

    New models of star-forming filamentary clouds are presented in order to quantify their properties and to predict their evolution. These 2D axisymmetric models describe filaments that have no core, one low-mass core, and one cluster-forming core. They are based on Plummer-like cylinders and spheroids that are bounded by a constant-density surface of finite extent. In contrast to 1D Plummer-like models, they have specific values of length and mass, they approximate observed column density maps, and their distributions of column density ( N -pdfs) are pole-free. Each model can estimate the star-forming potential of a core-filament system by identifying the zone of gas dense enough to form low-mass stars and by counting the number of enclosed thermal Jeans masses. This analysis suggests that the Musca central filament may be near the start of its star-forming life, with enough dense gas to make its first ∼3 protostars, while the Coronet filament is near the midpoint of its star formation, with enough dense gas to add ∼8 protostars to its ∼20 known stars. In contrast, L43 appears to be near the end of its star-forming life, since it lacks enough dense gas to add any new protostars to the two young stellar objectsalready known.

  19. Towards filament free semiconductor lasers

    DEFF Research Database (Denmark)

    McInerney, John; O'Brien, Peter; Skovgaard, Peter M. W.

    2000-01-01

    We outline physical models and simulations for suppression of self-focusing and filamentation in large aperture semiconductor lasers. The principal technical objective is to generate multi-watt CW or quasi-CW outputs with nearly diffraction limited beams, suitable for long distance free space...... propagation structures in lasers and amplifiers which suppress lateral reflections....

  20. Filament Winding. A Unified Approach

    NARCIS (Netherlands)

    Koussios, S.

    2004-01-01

    In this dissertation we have presented an overview and comprehensive treatment of several facets of the filament winding process. With the concepts of differential geometry and the theory of thin anisotropic shells of revolution, a parametric shape generator has been formulated for the design

  1. Ultraviolet treatment on high performance filaments

    International Nuclear Information System (INIS)

    Gu Huang

    2005-01-01

    Quartz, Kevlar, carbon, and glass filaments were irradiated by ultraviolet ray with various periods. Tensile strength of the treated fibres was tested and analyzed, and the outward appearance of the treated filaments was shown

  2. Role of Intermediate Filaments in Vesicular Traffic

    Directory of Open Access Journals (Sweden)

    Azzurra Margiotta

    2016-04-01

    Full Text Available Intermediate filaments are an important component of the cellular cytoskeleton. The first established role attributed to intermediate filaments was the mechanical support to cells. However, it is now clear that intermediate filaments have many different roles affecting a variety of other biological functions, such as the organization of microtubules and microfilaments, the regulation of nuclear structure and activity, the control of cell cycle and the regulation of signal transduction pathways. Furthermore, a number of intermediate filament proteins have been involved in the acquisition of tumorigenic properties. Over the last years, a strong involvement of intermediate filament proteins in the regulation of several aspects of intracellular trafficking has strongly emerged. Here, we review the functions of intermediate filaments proteins focusing mainly on the recent knowledge gained from the discovery that intermediate filaments associate with key proteins of the vesicular membrane transport machinery. In particular, we analyze the current understanding of the contribution of intermediate filaments to the endocytic pathway.

  3. Positrusion Filament Recycling System, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — TUI proposes a novel process to produce 3d printer feedstock filament out of scrap ABS on the ISS. Currently the plastic filament materials that most 3d printers use...

  4. Analysis of a filament stretching rheometer

    DEFF Research Database (Denmark)

    Kolte, Mette Irene; Rasmussen, Henrik K.; Hassager, Ole

    1996-01-01

    A finite element analysis of the stretching filament rheometer of Tirtaadmadja and Sridhar (1993) is presenetd. Simulations of the stretching of a filament of the polymet test solution, fluid A, between two plates are shown.......A finite element analysis of the stretching filament rheometer of Tirtaadmadja and Sridhar (1993) is presenetd. Simulations of the stretching of a filament of the polymet test solution, fluid A, between two plates are shown....

  5. Heterologous expression of an algal hydrogenase in a heterocystous cyanobacterium

    Energy Technology Data Exchange (ETDEWEB)

    Thorsten Heidorn; Peter Lindblad [Dept. of Physiological Botany, Uppsala University, Villavogen 6, SE-752 36 Uppsala, (Sweden)

    2006-07-01

    For the expression of an active algal [FeFe] hydrogenase in the heterocystous cyanobacterium Nostoc punctiforme A TCC 29133 the Chlamydomonas reinhardtii hydrogenase gene hydA1 and the accessory genes hydEF and hydG are to be introduced into the cyanobacteria cells. The genes were amplified by PCR from EST clones, cloned into the cloning vector pBluescript SK+ and sequenced. An expression vector for multi-cistronic cloning, based on pSCR202, was constructed and for a functional test GFP was inserted as a reporter gene. The GFP construct was transformed into Nostoc punctiforme A TCC 29133 by electroporation and expression of GFP was visualized by fluorescence microscopy. (authors)

  6. Heterologous expression of an algal hydrogenase in a heterocystous cyanobacterium

    International Nuclear Information System (INIS)

    Thorsten Heidorn; Peter Lindblad

    2006-01-01

    For the expression of an active algal [FeFe] hydrogenase in the heterocystous cyanobacterium Nostoc punctiforme A TCC 29133 the Chlamydomonas reinhardtii hydrogenase gene hydA1 and the accessory genes hydEF and hydG are to be introduced into the cyanobacteria cells. The genes were amplified by PCR from EST clones, cloned into the cloning vector pBluescript SK+ and sequenced. An expression vector for multi-cistronic cloning, based on pSCR202, was constructed and for a functional test GFP was inserted as a reporter gene. The GFP construct was transformed into Nostoc punctiforme A TCC 29133 by electroporation and expression of GFP was visualized by fluorescence microscopy. (authors)

  7. Ultraviolet radiation effects on pigmentation in the cyanobacterium ''Phormidium uncinatum''

    International Nuclear Information System (INIS)

    Donkor, V.A.; Haeder, D.P.

    1997-01-01

    The Baikal strain of the cyanobacterium Phormidium uncinatum was found to possess the photosynthetic pigments chlorophyll a, carotenoids, phycocyanin and allophycocyanin, while the Tuebingen strain of Phormidium contained, in addition to these, the biliprotein phycoerythrin. Sucrose gradient centrifugation of the pigment extracts resulted in a separation of the phycobiliproteins into several bands, which according to their absorption and fluorescence properties, were identified as monomers, trimers and hexamers. With increasing UV-B irradiation the heavier aggregates were broken down into smaller components. Photobleaching of these accessory pigments also occurred. FPLC gel filtration analyses of the pigments also showed loss of heavier aggregates of the phycobilins and bleaching of the pigments. SDS-polyacrylamide gel electrophoresis of the sucrose gradient and FPLC fractions indicated loss of the biliproteins with increasing UV-B irradiation. The loss of the β- were more rapid than that of the α- subunits. Increasing levels of ultraviolet irradiation is therefore deleterious to these organism. (author)

  8. Striation and convection in penumbral filaments

    NARCIS (Netherlands)

    Spruit, H.C.; Scharmer, G.B.; Löfdahl, M.G.

    2010-01-01

    Observations with the 1-m Swedish Solar Telescope of the flows seen in penumbral filaments are presented. Time sequences of bright filaments show overturning motions strikingly similar to those seen along the walls of small isolated structures in the active regions. The filaments show outward

  9. Photosynthetic versatility in the genome of Geitlerinema sp. PCC 9228 (formerly Oscillatoria limnetica ‘Solar Lake’, a model anoxygenic photosynthetic cyanobacterium

    Directory of Open Access Journals (Sweden)

    Sharon L Grim

    2016-10-01

    Full Text Available Anoxygenic cyanobacteria that use sulfide as the electron donor for photosynthesis are a potentially influential but poorly constrained force on Earth’s biogeochemistry. Their versatile metabolism may have boosted primary production and nitrogen cycling in euxinic coastal margins in the Proterozoic. In addition, they represent a biological mechanism for limiting the accumulation of atmospheric oxygen, especially before the Great Oxidation Event and in the low-oxygen conditions of the Proterozoic. In this study, we describe the draft genome sequence of Geitlerinema sp. PCC 9228, formerly Oscillatoria limnetica ‘Solar Lake’, a mat-forming diazotrophic cyanobacterium that can switch between oxygenic photosynthesis and sulfide-based anoxygenic photosynthesis. Geitlerinema possesses three variants of psbA, which encodes protein D1, a core component of the photosystem II reaction center. Phylogenetic analyses indicate that one variant is closely affiliated with cyanobacterial psbA genes that code for a D1 protein used for oxygen-sensitive processes. Another version is phylogenetically similar to cyanobacterial psbA genes that encode D1 proteins used under microaerobic conditions, and the third variant may be cued to high light and/or elevated oxygen concentrations. Geitlerinema has the canonical gene for sulfide quinone reductase (SQR used in cyanobacterial anoxygenic photosynthesis and a putative transcriptional regulatory gene in the same operon. Another operon with a second, distinct sqr and regulatory gene is present, and is phylogenetically related to sqr genes used for high sulfide concentrations. The genome has a comprehensive nif gene suite for nitrogen fixation, supporting previous observations of nitrogenase activity. Geitlerinema possesses a bidirectional hydrogenase rather than the uptake hydrogenase typically used by cyanobacteria in diazotrophy. Overall, the genome sequence of Geitlerinema sp. PCC 9228 highlights potential

  10. Photosynthetic Versatility in the Genome of Geitlerinema sp. PCC 9228 (Formerly Oscillatoria limnetica ‘Solar Lake’), a Model Anoxygenic Photosynthetic Cyanobacterium

    Science.gov (United States)

    Grim, Sharon L.; Dick, Gregory J.

    2016-01-01

    Anoxygenic cyanobacteria that use sulfide as the electron donor for photosynthesis are a potentially influential but poorly constrained force on Earth’s biogeochemistry. Their versatile metabolism may have boosted primary production and nitrogen cycling in euxinic coastal margins in the Proterozoic. In addition, they represent a biological mechanism for limiting the accumulation of atmospheric oxygen, especially before the Great Oxidation Event and in the low-oxygen conditions of the Proterozoic. In this study, we describe the draft genome sequence of Geitlerinema sp. PCC 9228, formerly Oscillatoria limnetica ‘Solar Lake’, a mat-forming diazotrophic cyanobacterium that can switch between oxygenic photosynthesis and sulfide-based anoxygenic photosynthesis (AP). Geitlerinema possesses three variants of psbA, which encodes protein D1, a core component of the photosystem II reaction center. Phylogenetic analyses indicate that one variant is closely affiliated with cyanobacterial psbA genes that code for a D1 protein used for oxygen-sensitive processes. Another version is phylogenetically similar to cyanobacterial psbA genes that encode D1 proteins used under microaerobic conditions, and the third variant may be cued to high light and/or elevated oxygen concentrations. Geitlerinema has the canonical gene for sulfide quinone reductase (SQR) used in cyanobacterial AP and a putative transcriptional regulatory gene in the same operon. Another operon with a second, distinct sqr and regulatory gene is present, and is phylogenetically related to sqr genes used for high sulfide concentrations. The genome has a comprehensive nif gene suite for nitrogen fixation, supporting previous observations of nitrogenase activity. Geitlerinema possesses a bidirectional hydrogenase rather than the uptake hydrogenase typically used by cyanobacteria in diazotrophy. Overall, the genome sequence of Geitlerinema sp. PCC 9228 highlights potential cyanobacterial strategies to cope with

  11. Temporal symmetry of individual filaments in different spatial symmetry filaments pattern in a dielectric barrier discharge

    International Nuclear Information System (INIS)

    Dong, L. F.; Xiao, H.; Fan, W. L.; Yin, Z. Q.; Zhao, H. T.

    2010-01-01

    The temporal behavior of individual filament in different spatial symmetry filaments patterns in dielectric barrier discharge is investigated by using an optical method. A series of return maps of the discharge moments of individual filaments is given. It is found that the temporal symmetry of individual filament changes with the change of the spatial symmetry of filaments pattern as the applied voltage increases. The role of wall charges for this phenomenon is analyzed.

  12. Transcription and Regulation of the Bidirectional Hydrogenase in the Cyanobacterium Nostoc sp. Strain PCC 7120▿

    Science.gov (United States)

    Sjöholm, Johannes; Oliveira, Paulo; Lindblad, Peter

    2007-01-01

    The filamentous, heterocystous cyanobacterium Nostoc sp. strain PCC 7120 (Anabaena sp. strain PCC 7120) possesses an uptake hydrogenase and a bidirectional enzyme, the latter being capable of catalyzing both H2 production and evolution. The completely sequenced genome of Nostoc sp. strain PCC 7120 reveals that the five structural genes encoding the bidirectional hydrogenase (hoxEFUYH) are separated in two clusters at a distance of approximately 8.8 kb. The transcription of the hox genes was examined under nitrogen-fixing conditions, and the results demonstrate that the cluster containing hoxE and hoxF can be transcribed as one polycistronic unit together with the open reading frame alr0750. The second cluster, containing hoxU, hoxY, and hoxH, is transcribed together with alr0763 and alr0765, located between the hox genes. Moreover, alr0760 and alr0761 form an additional larger operon. Nevertheless, Northern blot hybridizations revealed a rather complex transcription pattern in which the different hox genes are expressed differently. Transcriptional start points (TSPs) were identified 66 and 57 bp upstream from the start codon of alr0750 and hoxU, respectively. The transcriptions of the two clusters containing the hox genes are both induced under anaerobic conditions concomitantly with the induction of a higher level of hydrogenase activity. An additional TSP, within the annotated alr0760, 244 bp downstream from the suggested translation start codon, was identified. Electrophoretic mobility shift assays with purified LexA from Nostoc sp. strain PCC 7120 demonstrated specific interactions between the transcriptional regulator and both hox promoter regions. However, when LexA from Synechocystis sp. strain PCC 6803 was used, the purified protein interacted only with the promoter region of the alr0750-hoxE-hoxF operon. A search of the whole Nostoc sp. strain PCC 7120 genome demonstrated the presence of 216 putative LexA binding sites in total, including recA and rec

  13. Microwave processing of ceramic oxide filaments

    Energy Technology Data Exchange (ETDEWEB)

    Vogt, G.J.; Katz, J.D. [Los Alamos National Laboratory, NM (United States)

    1995-05-01

    The objective of the microwave filament processing project is to develop microwave techniques at 2.45 GHZ to manufacture continuous ceramic oxide filaments. Microwave processing uses the volumetric absorption of microwave power in oxide filament tows to drive off process solvents, to burn out organic binders, and to sinter the dried fibers to produce flexible, high-strength ceramic filaments. The technical goal is to advance filament processing technology by microwave heating more rapidly with less energy and at a lower cost than conventional processing, but with the same quality as conventional processing. The manufacturing goal is to collaborate with the 3M Company, a US manufacturer of ceramic oxide filaments, to evaluate the technology using a prototype filament system and to transfer the microwave technology to the 3M Company.

  14. Temperature distributions of a conductively heated filament

    International Nuclear Information System (INIS)

    Tamura, Koji; Ohba, Hironori; Shibata, Takemasa

    1999-07-01

    Temperature distributions of a heated filament were measured. A W-Re(5%) filament (0.25 mm in diameter, 24.7 mm in length) was conductively heated by currents between 5A and 7A with a DC power supply, and the surface of the filament was imaged with a charge coupled device (CCD) camera through a monochromatic filter. The spectral radiation intensity at the filament center region was almost uniform. Since the temperature distribution was also uniform and the energy loss by thermal conduction was negligible, temperature in this region was determined from the energy balance between applied power and radiation loss. Temperature distribution of the filament was determined based on the Planck's law of radiation from the spectral radiation intensity ratio of the filament surface using obtained temperature as a reference. It was found that temperature distribution of a filament was easily measured by this method. (author)

  15. Filament instability under constant loads

    Science.gov (United States)

    Monastra, A. G.; Carusela, M. F.; D’Angelo, M. V.; Bruno, L.

    2018-04-01

    Buckling of semi-flexible filaments appears in different systems and scales. Some examples are: fibers in geophysical applications, microtubules in the cytoplasm of eukaryotic cells and deformation of polymers freely suspended in a flow. In these examples, instabilities arise when a system’s parameter exceeds a critical value, being the Euler force the most known. However, the complete time evolution and wavelength of buckling processes are not fully understood. In this work we solve analytically the time evolution of a filament under a constant compressive force in the small amplitude approximation. This gives an insight into the variable force scenario in terms of normal modes. The evolution is highly sensitive to the initial configuration and to the magnitude of the compressive load. This model can be a suitable approach to many different real situations.

  16. Lighting the universe with filaments.

    Science.gov (United States)

    Gao, Liang; Theuns, Tom

    2007-09-14

    The first stars in the universe form when chemically pristine gas heats as it falls into dark-matter potential wells, cools radiatively because of the formation of molecular hydrogen, and becomes self-gravitating. Using supercomputer simulations, we demonstrated that the stars' properties depend critically on the currently unknown nature of the dark matter. If the dark-matter particles have intrinsic velocities that wipe out small-scale structure, then the first stars form in filaments with lengths on the order of the free-streaming scale, which can be approximately 10(20) meters (approximately 3 kiloparsecs, corresponding to a baryonic mass of approximately 10(7) solar masses) for realistic "warm dark matter" candidates. Fragmentation of the filaments forms stars with a range of masses, which may explain the observed peculiar element abundance pattern of extremely metal-poor stars, whereas coalescence of fragments and stars during the filament's ultimate collapse may seed the supermassive black holes that lurk in the centers of most massive galaxies.

  17. Spatial separation of photosynthesis and ethanol production by cell type-specific metabolic engineering of filamentous cyanobacteria.

    Science.gov (United States)

    Ehira, Shigeki; Takeuchi, Takuto; Higo, Akiyoshi

    2018-02-01

    Cyanobacteria, which perform oxygenic photosynthesis, have drawn attention as hosts for the direct production of biofuels and commodity chemicals from CO 2 and H 2 O using light energy. Although cyanobacteria capable of producing diverse chemicals have been generated by metabolic engineering, anaerobic non-photosynthetic culture conditions are often necessary for their production. In this study, we conducted cell type-specific metabolic engineering of the filamentous cyanobacterium Anabaena sp. PCC 7120, which forms a terminally differentiated cell called a heterocyst with a semi-regular spacing of 10-15 cells. Because heterocysts are specialized cells for nitrogen fixation, the intracellular oxygen level of heterocysts is maintained very low even when adjacent cells perform oxygenic photosynthesis. Pyruvate decarboxylase of Zymomonas mobilis and alcohol dehydrogenase of Synechocystis sp. PCC 6803 were exclusively expressed in heterocysts. Ethanol production was concomitant with nitrogen fixation in genetically engineered Anabaena sp. PCC 7120. Engineering of carbon metabolism in heterocysts improved ethanol production, and strain ET14, with an extra copy of the invB gene expressed from a heterocyst-specific promoter, produced 130.9 mg L -1 of ethanol after 9 days. ET14 produced 1681.9 mg L -1 of ethanol by increasing the CO 2 supply. Ethanol production per heterocyst cell was approximately threefold higher than that per cell of unicellular cyanobacterium. This study demonstrates the potential of heterocysts for anaerobic production of biofuels and commodity chemicals under oxygenic photosynthetic conditions.

  18. Binding characteristics of copper and cadmium by cyanobacterium Spirulina platensis.

    Science.gov (United States)

    Fang, Linchuan; Zhou, Chen; Cai, Peng; Chen, Wenli; Rong, Xingmin; Dai, Ke; Liang, Wei; Gu, Ji-Dong; Huang, Qiaoyun

    2011-06-15

    Cyanobacteria are promising biosorbent for heavy metals in bioremediation. Although sequestration of metals by cyanobacteria is known, the actual mechanisms and ligands involved are not very well understood. The binding characteristics of Cu(II) and Cd(II) by the cyanobacterium Spirulina platensis were investigated using a combination of chemical modifications, batch adsorption experiments, Fourier transform infrared (FTIR) spectroscopy and X-ray absorption fine structure (XAFS) spectroscopy. A significant increase in Cu(II) and Cd(II) binding was observed in the range of pH 3.5-5.0. Dramatical decrease in adsorption of Cu(II) and Cd(II) was observed after methanol esterification of the nonliving cells demonstrating that carboxyl functional groups play an important role in the binding of metals by S. platensis. The desorption rate of Cu(II) and Cd(II) from S. platensis surface was 72.7-80.7% and 53.7-58.0% by EDTA and NH(4)NO(3), respectively, indicating that ion exchange and complexation are the dominating mechanisms for Cu(II) and Cd(II) adsorption. XAFS analysis provided further evidence on the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. Two New Lyngbyatoxin Derivatives from the Cyanobacterium, Moorea producens

    Directory of Open Access Journals (Sweden)

    Weina Jiang

    2014-12-01

    Full Text Available The toxin-producing cyanobacterium, Moorea producens, is a known causative organism of food poisoning and seaweed dermatitis (also known as “swimmer’s itch”. Two new toxic compounds were isolated and structurally elucidated from an ethyl acetate extract of M. producens collected from Hawaii. Analyses of HR-ESI-MS and NMR spectroscopies, as well as optical rotations and CD spectra indicated two new lyngbyatoxin derivatives, 2-oxo-3(R-hydroxy-lyngbyatoxin A (1 and 2-oxo-3(R-hydroxy-13-N-desmethyl-lyngbyatoxin A (2. The cytotoxicity and lethal activities of 1 and 2 were approximately 10- to 150-times less potent than lyngbyatoxin A. Additionally, the binding activities of 1 and 2 possessed 10,000-times lower affinity for the protein kinase Cδ (PKCδ-C1B peptide when compared to lyngbyatoxin A. These findings suggest that these new lyngbyatoxin derivatives may mediate their acute toxicities through a non-PKC activation pathway.

  20. Nitrogen-fixing cyanobacterium with a high phycoerythrin content.

    Science.gov (United States)

    Rodriguez, H; Rivas, J; Guerrero, M G; Losada, M

    1989-03-01

    The elemental and molecular composition, pigment content, and productivity of a phycoerythrin-rich nitrogen-fixing cyanobacterium-an Anabaena strain isolated from the coastal lagoon Albufera de Valencia, Spain-has been investigated. When compared with other heterocystous species, this strain exhibits similar chlorophyll a, carotene, and total phycobiliprotein contents but differs remarkably in the relative proportion of specific phycobiliproteins; the content of C-phycoerythrin amounts to 8.3% (versus about 1% in the other species) of cell dry weight. Absorption and fluorescence spectra of intact phycobilisomes isolated from this Anabaena sp. corroborate the marked contribution of phycoerythrin as an antenna pigment, a circumstance that is unusual for cyanobacteria capable of fixing N(2). The pigment content of cells is affected by variations in irradiance and cell density, these adaptive changes being more patent for C-phycoerythrin than for phycocyanins. The Anabaena strain is clumpy and capable of rapid flocculation. It exhibits outdoor productivities higher than 20 g (dry weight) m day during summer.

  1. The Mysterious Case of the Missing Filaments

    Science.gov (United States)

    Alden, C. R.

    2016-12-01

    Coronal Mass Ejections, or CMEs, are large solar eruptions that can have major debilitating impacts on society. Typically, these eruptions have the three following key structures: the leading edge, the empty chamber known as the cavity, and the filament which often is the brightest part of the CME. When we can see all three structures clearly with a coronagraph, it is called a classic three-part CME, also referred to as a 'lightbulb' CME. According to current knowledge, when a CME erupts, a filament should also erupt or lift off the Sun in order to have the bright center within the CME. However, we do not always see a filament erupt at the surface, and yet we still get a 'filament' within the coronagraph CME. To better understand what might be occurring with these missing filaments, we looked at three-part CMEs using the SOHO LASCO CME Catalog and filaments from the SDO AIA Filament Catalog in order to create a list of 50 CMEs without a listed filament erupting at the surface. For those CMEs without filaments in the list we closely inspected the AIA images for evidence of filament eruption. To ensure that there were no filaments past the limb of the Sun, we used data from the STEREO-A and STEREO-B spacecraft's to look at the Sun from other angles. We have found numerous events where no filament erupts from the surface, but we still see the classic three-part CME. We believe this may be due to an optical illusion occurring from the twisting of the flux rope.

  2. Fine filament NbTi superconductive composite

    International Nuclear Information System (INIS)

    Hong, S.; Grabinsky, G.; Marancik, W.; Pattanayak, D.

    1986-01-01

    The large superconducting magnet for the high energy physics accelerator requires fine filament composite to minimize the field error due to the persistent current in the filaments. New concepts toward the fine filament composite and its cable fabrication are discussed. Two-stage cables of fine wire with intermediate number of filaments were introduced. The first stage was six wires cables around one and in the second stage this was used to produce a Rutherford cable. The advantage of this process is in the ease of billet fabrication since the number of filaments in a single wire is within the range of easy billet fabrication. The disadvantage is in the cable fabrication. One of the major concerns in the fabrication of fine NbTi filaments composite in a copper matrix is the intermetallic compound formation during the extrusion and heat treatment steps. The hard intermetallic particles degrade the uniformity of the filaments and reduce the critical current density. The process of using Nb barrier between the filaments and copper matrix in order to prevent this CuTi intermetallic particle formation is described

  3. Prediction of Solar Eruptions Using Filament Metadata

    Science.gov (United States)

    Aggarwal, Ashna; Schanche, Nicole; Reeves, Katharine K.; Kempton, Dustin; Angryk, Rafal

    2018-05-01

    We perform a statistical analysis of erupting and non-erupting solar filaments to determine the properties related to the eruption potential. In order to perform this study, we correlate filament eruptions documented in the Heliophysics Event Knowledgebase (HEK) with HEK filaments that have been grouped together using a spatiotemporal tracking algorithm. The HEK provides metadata about each filament instance, including values for length, area, tilt, and chirality. We add additional metadata properties such as the distance from the nearest active region and the magnetic field decay index. We compare trends in the metadata from erupting and non-erupting filament tracks to discover which properties present signs of an eruption. We find that a change in filament length over time is the most important factor in discriminating between erupting and non-erupting filament tracks, with erupting tracks being more likely to have decreasing length. We attempt to find an ensemble of predictive filament metadata using a Random Forest Classifier approach, but find the probability of correctly predicting an eruption with the current metadata is only slightly better than chance.

  4. Scanning For Hotspots In Lamp Filaments

    Science.gov (United States)

    Powers, Charles E.; Van Sant, Tim; Leidecker, Henning

    1993-01-01

    Scanning photometer designed for use in investigation of failures of incandescent lamp filaments. Maps brightness as function of position along each filament to identify bright (hot) spots, occurring at notches and signifying incipient breaks or rewelds. Also used to measure nonuniformity in outputs of such linear devices as light-emitting diodes, and to measure diffraction patterns of lenses.

  5. Binding characteristics of copper and cadmium by cyanobacterium Spirulina platensis

    International Nuclear Information System (INIS)

    Fang Linchuan; Zhou Chen; Cai Peng; Chen Wenli; Rong Xingmin; Dai Ke; Liang Wei; Gu Jidong; Huang Qiaoyun

    2011-01-01

    Highlights: → The carboxyl groups play a vital role in the binding of Cu(II) and Cd(II) to S. platensis cells. → Ion exchange and complexation are the dominating mechanism for Cu(II) and Cd(II) adsorption. → XAFS analysis provided evidence for the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface. - Abstract: Cyanobacteria are promising biosorbent for heavy metals in bioremediation. Although sequestration of metals by cyanobacteria is known, the actual mechanisms and ligands involved are not very well understood. The binding characteristics of Cu(II) and Cd(II) by the cyanobacterium Spirulina platensis were investigated using a combination of chemical modifications, batch adsorption experiments, Fourier transform infrared (FTIR) spectroscopy and X-ray absorption fine structure (XAFS) spectroscopy. A significant increase in Cu(II) and Cd(II) binding was observed in the range of pH 3.5-5.0. Dramatical decrease in adsorption of Cu(II) and Cd(II) was observed after methanol esterification of the nonliving cells demonstrating that carboxyl functional groups play an important role in the binding of metals by S. platensis. The desorption rate of Cu(II) and Cd(II) from S. platensis surface was 72.7-80.7% and 53.7-58.0% by EDTA and NH 4 NO 3 , respectively, indicating that ion exchange and complexation are the dominating mechanisms for Cu(II) and Cd(II) adsorption. XAFS analysis provided further evidence on the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface.

  6. Binding characteristics of copper and cadmium by cyanobacterium Spirulina platensis

    Energy Technology Data Exchange (ETDEWEB)

    Fang Linchuan [State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070 (China); Zhou Chen; Cai Peng [Key Laboratory of Subtropical Agricultural Resources and Environment, Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China); Chen Wenli [State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070 (China); Rong Xingmin; Dai Ke; Liang Wei [Key Laboratory of Subtropical Agricultural Resources and Environment, Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China); Gu Jidong [Department of Ecology and Biodiversity, University of Hong Kong, Pokfulam Road, Hong Kong (Hong Kong); Huang Qiaoyun, E-mail: qyhuang@mail.hzau.edu.cn [State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070 (China); Key Laboratory of Subtropical Agricultural Resources and Environment, Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China)

    2011-06-15

    Highlights: {yields} The carboxyl groups play a vital role in the binding of Cu(II) and Cd(II) to S. platensis cells. {yields} Ion exchange and complexation are the dominating mechanism for Cu(II) and Cd(II) adsorption. {yields} XAFS analysis provided evidence for the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface. - Abstract: Cyanobacteria are promising biosorbent for heavy metals in bioremediation. Although sequestration of metals by cyanobacteria is known, the actual mechanisms and ligands involved are not very well understood. The binding characteristics of Cu(II) and Cd(II) by the cyanobacterium Spirulina platensis were investigated using a combination of chemical modifications, batch adsorption experiments, Fourier transform infrared (FTIR) spectroscopy and X-ray absorption fine structure (XAFS) spectroscopy. A significant increase in Cu(II) and Cd(II) binding was observed in the range of pH 3.5-5.0. Dramatical decrease in adsorption of Cu(II) and Cd(II) was observed after methanol esterification of the nonliving cells demonstrating that carboxyl functional groups play an important role in the binding of metals by S. platensis. The desorption rate of Cu(II) and Cd(II) from S. platensis surface was 72.7-80.7% and 53.7-58.0% by EDTA and NH{sub 4}NO{sub 3}, respectively, indicating that ion exchange and complexation are the dominating mechanisms for Cu(II) and Cd(II) adsorption. XAFS analysis provided further evidence on the inner-sphere complexation of Cu by carboxyl ligands and showed that Cu is complexed by two 5-membered chelate rings on S. platensis surface.

  7. Helical beating of an actuated elastic filament

    International Nuclear Information System (INIS)

    Coq, Nais; Roure, Olivia du; Fermigier, Marc; Bartolo, Denis

    2009-01-01

    We investigate the propulsive force resulting from the rotation of a flexible filament in the low Reynolds number regime. Using a simple linear model, we establish the nonlinear torque-force relations for two torque-driven actuation modes. When the rotation of the filament is induced by two perpendicular transverse oscillating torques, the propulsive force increases monotonically with the torque amplitude. Conversely, when a constant axial torque is applied, the torque-force characteristics displays an unstable branch, related to a discontinuous transition in the shape of the filament. We characterize this shape transition using two geometrical parameters, quantifying the wrapping around and the collapse on the axis of the filament. The proposed theoretical description correctly accounts for our experimental observations and reveals a strong dependence of the filament dynamics on the anchoring conditions.

  8. Filamentous Growth in Eremothecium Fungi

    DEFF Research Database (Denmark)

    Oskarsson, Therese

    , this thesis deals with some of the aspects of hyphal growth, which is an important virulence factor for pathogenic fungi infecting both humans and plants. Hyphal establishment through continuous polar growth is a complex process, requiring the careful coordination of a large subset of proteins involved......-regulatory activity of AgGts1, the protein could have additional actin organizing properties. In the second and third part, this thesis addresses the use of A. gossypii and its relative E. cymbalariae as model organisms for filamentous growth. A series of assays analyzed the capability of Eremothecium genus fungi...... of molecular tools for E. cymbalariae to enable a faster and more efficient approach for genetic comparisons between Eremothecium genus fungi....

  9. Particles trajectories in magnetic filaments

    International Nuclear Information System (INIS)

    Bret, A.

    2015-01-01

    The motion of a particle in a spatially harmonic magnetic field is a basic problem involved, for example, in the mechanism of formation of a collisionless shock. In such settings, it is generally reasoned that particles entering a Weibel generated turbulence are trapped inside it, provided their Larmor radius in the peak field is smaller than the field coherence length. The goal of this work is to put this heuristic conclusion on firm ground by studying, both analytically and numerically, such motion. A toy model is analyzed, consisting of a relativistic particle entering a region of space occupied by a spatially harmonic field. The particle penetrates the magnetic structure in a direction aligned with the magnetic filaments. Although the conclusions are not trivial, the main result is confirmed

  10. Particles trajectories in magnetic filaments

    Science.gov (United States)

    Bret, A.

    2015-07-01

    The motion of a particle in a spatially harmonic magnetic field is a basic problem involved, for example, in the mechanism of formation of a collisionless shock. In such settings, it is generally reasoned that particles entering a Weibel generated turbulence are trapped inside it, provided their Larmor radius in the peak field is smaller than the field coherence length. The goal of this work is to put this heuristic conclusion on firm ground by studying, both analytically and numerically, such motion. A toy model is analyzed, consisting of a relativistic particle entering a region of space occupied by a spatially harmonic field. The particle penetrates the magnetic structure in a direction aligned with the magnetic filaments. Although the conclusions are not trivial, the main result is confirmed.

  11. Particles trajectories in magnetic filaments

    Energy Technology Data Exchange (ETDEWEB)

    Bret, A. [ETSI Industriales, Universidad de Castilla-La Mancha, 13071 Ciudad Real (Spain); Instituto de Investigaciones Energéticas y Aplicaciones Industriales, Campus Universitario de Ciudad Real, 13071 Ciudad Real (Spain)

    2015-07-15

    The motion of a particle in a spatially harmonic magnetic field is a basic problem involved, for example, in the mechanism of formation of a collisionless shock. In such settings, it is generally reasoned that particles entering a Weibel generated turbulence are trapped inside it, provided their Larmor radius in the peak field is smaller than the field coherence length. The goal of this work is to put this heuristic conclusion on firm ground by studying, both analytically and numerically, such motion. A toy model is analyzed, consisting of a relativistic particle entering a region of space occupied by a spatially harmonic field. The particle penetrates the magnetic structure in a direction aligned with the magnetic filaments. Although the conclusions are not trivial, the main result is confirmed.

  12. Actin filaments as tension sensors.

    Science.gov (United States)

    Galkin, Vitold E; Orlova, Albina; Egelman, Edward H

    2012-02-07

    The field of mechanobiology has witnessed an explosive growth over the past several years as interest has greatly increased in understanding how mechanical forces are transduced by cells and how cells migrate, adhere and generate traction. Actin, a highly abundant and anomalously conserved protein, plays a large role in forming the dynamic cytoskeleton that is so essential for cell form, motility and mechanosensitivity. While the actin filament (F-actin) has been viewed as dynamic in terms of polymerization and depolymerization, new results suggest that F-actin itself may function as a highly dynamic tension sensor. This property may help explain the unusual conservation of actin's sequence, as well as shed further light on actin's essential role in structures from sarcomeres to stress fibers. Copyright © 2012 Elsevier Ltd. All rights reserved.

  13. Filament Activation in Response to Magnetic Flux Emergence and Cancellation in Filament Channels

    Science.gov (United States)

    Li, Ting; Zhang, Jun; Ji, Haisheng

    2015-06-01

    We conducted a comparative analysis of two filaments that showed a quite different activation in response to the flux emergence within the filament channels. The observations from the Solar Dynamics Observatory (SDO) and Global Oscillation Network Group (GONG) were made to analyze the two filaments on 2013 August 17 - 20 (SOL2013-08-17) and September 29 (SOL2013-09-29). The first event showed that the main body of the filament was separated into two parts when an active region (AR) emerged with a maximum magnetic flux of about 6.4×1021 Mx underlying the filament. The close neighborhood and common direction of the bright threads in the filament and the open AR fan loops suggest a similar magnetic connectivity of these two flux systems. The equilibrium of the filament was not destroyed three days after the start of the emergence of the AR. To our knowledge, similar observations have never been reported before. In the second event, the emerging flux occurred nearby a barb of the filament with a maximum magnetic flux of 4.2×1020 Mx, about one order of magnitude lower than that of the first event. Two patches of parasitic polarity in the vicinity of the barb merged, then cancelled with nearby network fields. About 20 hours after the onset of the emergence, the filament erupted. Our findings imply that the location of emerging flux within the filament channel is probably crucial to filament evolution. If the flux emergence appears nearby the barbs, it is highly likely that the emerging flux and the filament magnetic fields will cancel, which may lead to the eruption of the filament. The comparison of the two events shows that the emergence of a small AR may still not be enough to disrupt the stability of a filament system, and the actual eruption only occurs after the flux cancellation sets in.

  14. Hydrogen sulfide can inhibit and enhance oxygenic photosynthesis in a cyanobacterium from sulfidic springs

    NARCIS (Netherlands)

    Klatt, Judith M.; Haas, Sebastian; Yilmaz, Pelin; de Beer, Dirk; Polerecky, Lubos

    We used microsensors to investigate the combinatory effect of hydrogen sulfide (H2S) and light on oxygenic photosynthesis in biofilms formed by a cyanobacterium from sulfidic springs. We found that photosynthesis was both positively and negatively affected by H2S: (i) H2S accelerated the recovery of

  15. Genome Sequence of the Thermophilic Cyanobacterium Thermosynechococcus sp. Strain NK55a.

    Energy Technology Data Exchange (ETDEWEB)

    Stolyar, Sergey; Liu, Zhenfeng; Thiel, Vera; Tomsho, Lynn P.; Pinel, Nicolas; Nelson, William C.; Lindemann, Stephen R.; Romine, Margaret F.; Haruta, Shin; Schuster, Stephan C.; Bryant, Donald A.; Fredrickson, Jim K.

    2014-01-02

    The genome of the unicellular cyanobacterium, Thermosynechococcus sp. strain NK55a, isolated from Nakabusa hot spring, comprises a single, circular, 2.5-Mb chromosome. The genome is predicted to encode 2358 protein coding genes, including genes for all typical cyanobacterial photosynthetic and metabolic functions. No genes encoding hydrogenases or nitrogenase were identified.

  16. Highly plastic genome of Microcystis aeruginosa PCC 7806, a ubiquitous toxic freshwater cyanobacterium

    NARCIS (Netherlands)

    Frangeul, L.; Quillardet, P.; Castets, A.M.; Humbert, J.F.; Matthijs, H.C.P.; Cortez, D.; Tolonen, A.; Zhang, C.C.; Gribaldo, S.; Kehr, J.C.; Zilliges, Y.; Ziemert, N.; Becker, S.; Talla, E.; Latifi, A.; Billault, A.; Lepelletier, A.; Dittmann, E.; Bouchier, C.; Tandeau de Marsac, N.

    2008-01-01

    Background The colonial cyanobacterium Microcystis proliferates in a wide range of freshwater ecosystems and is exposed to changing environmental factors during its life cycle. Microcystis blooms are often toxic, potentially fatal to animals and humans, and may cause environmental problems. There

  17. Competition and facilitation between the marine nitrogen-fixing cyanobacterium Cyanothece and its associated bacterial community

    NARCIS (Netherlands)

    Brauer, Verena S; Stomp, Maayke; Bouvier, Thierry; Fouilland, Eric; Leboulanger, Christophe; Confurius-Guns, Veronique; Weissing, Franz J; Stal, Lucas J; Huisman, Jef

    2015-01-01

    N2-fixing cyanobacteria represent a major source of new nitrogen and carbon for marine microbial communities, but little is known about their ecological interactions with associated microbiota. In this study we investigated the interactions between the unicellular N2-fixing cyanobacterium Cyanothece

  18. Effect of Selected Plant Extracts and D- and L-Lysine on the Cyanobacterium Microcystis aeruginosa

    NARCIS (Netherlands)

    Lurling, M.F.L.L.W.; Oosterhout, J.F.X.

    2014-01-01

    We tested extracts from Fructus mume, Salvia miltiorrhiza and Moringa oleifera as well as L-lysine and D-Lysine as curative measures to rapidly suppress the cyanobacterium Microcystis aeruginosa NIVA-CYA 43. We tested these compounds under similar conditions to facilitate comparisons. We

  19. Unwinding motion of a twisted active region filament

    Energy Technology Data Exchange (ETDEWEB)

    Yan, X. L.; Xue, Z. K.; Kong, D. F. [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Liu, J. H. [Department of Physics, Shijiazhuang University, Shijiazhuang 050035 (China); Xu, C. L. [Yunnan Normal University, Kunming 650092 (China)

    2014-12-10

    To better understand the structures of active region filaments and the eruption process, we study an active region filament eruption in active region NOAA 11082 in detail on 2010 June 22. Before the filament eruption, the opposite unidirectional material flows appeared in succession along the spine of the filament. The rising of the filament triggered two B-class flares at the upper part of the filament. As the bright material was injected into the filament from the sites of the flares, the filament exhibited a rapid uplift accompanying the counterclockwise rotation of the filament body. From the expansion of the filament, we can see that the filament consisted of twisted magnetic field lines. The total twist of the filament is at least 5π obtained by using a time slice method. According to the morphology change during the filament eruption, it is found that the active region filament was a twisted flux rope and its unwinding motion was like a solar tornado. We also find that there was a continuous magnetic helicity injection before and during the filament eruption. It is confirmed that magnetic helicity can be transferred from the photosphere to the filament. Using the extrapolated potential fields, the average decay index of the background magnetic fields over the filament is 0.91. Consequently, these findings imply that the mechanism of solar filament eruption could be due to the kink instability and magnetic helicity accumulation.

  20. Automatic Detect and Trace of Solar Filaments

    Science.gov (United States)

    Fang, Cheng; Chen, P. F.; Tang, Yu-hua; Hao, Qi; Guo, Yang

    We developed a series of methods to automatically detect and trace solar filaments in solar Hα images. The programs are able to not only recognize filaments and determine their properties, such as the position, the area and other relevant parameters, but also to trace the daily evolution of the filaments. For solar full disk Hα images, the method consists of three parts: first, preprocessing is applied to correct the original images; second, the Canny edge-detection method is used to detect the filaments; third, filament properties are recognized through the morphological operators. For each Hα filament and its barb features, we introduced the unweighted undirected graph concept and adopted Dijkstra shortest-path algorithm to recognize the filament spine; then, using polarity inversion line shift method for measuring the polarities in both sides of the filament to determine the filament axis chirality; finally, employing connected components labeling method to identify the barbs and calculating the angle between each barb and spine to indicate the barb chirality. Our algorithms are applied to the observations from varied observatories, including the Optical & Near Infrared Solar Eruption Tracer (ONSET) in Nanjing University, Mauna Loa Solar Observatory (MLSO) and Big Bear Solar Observatory (BBSO). The programs are demonstrated to be effective and efficient. We used our method to automatically process and analyze 3470 images obtained by MLSO from January 1998 to December 2009, and a butterfly diagram of filaments is obtained. It shows that the latitudinal migration of solar filaments has three trends in the Solar Cycle 23: The drift velocity was fast from 1998 to the solar maximum; after the solar maximum, it became relatively slow and after 2006, the migration became divergent, signifying the solar minimum. About 60% filaments with the latitudes larger than 50 degree migrate towards the Polar Regions with relatively high velocities, and the latitudinal migrating

  1. Filamentation of Campylobacter in broth cultures

    Directory of Open Access Journals (Sweden)

    Nacheervan M Ghaffar

    2015-06-01

    Full Text Available The transition from rod to filamentous cell morphology has been identified as a response to stressful conditions in many bacterial species and has been ascribed to confer certain survival advantages. Filamentation of Campylobacter jejuni was demonstrated to occur spontaneously on entry in to stationary phase distinguishing it from many other bacteria where a reduction in size is more common. The aim of this study was to investigate the cues that give rise to filamentation of C. jejuni and C. coli and gain insights into the process. Using minimal medium, augmentation of filamentation occurred and it was observed that this morphological change was wide spread amongst C. jejuni strains tested but was not universal in C. coli strains. Filamentation did not appear to be due to release of diffusible molecules, toxic metabolites, or be in response to oxidative stress in the medium. Separated filaments exhibited greater intracellular ATP contents (2.66 to 17.4 fg than spiral forms (0.99 to 1.7 fg and showed enhanced survival in water at 4oC and 37oC compared to spiral cells. These observations support the conclusion that the filaments are adapted to survive extra-intestinal environments. Differences in cell morphology and physiology need to be considered in the context of the design of experimental studies and the methods adopted for the isolation of campylobacters from food, clinical and environmental sources.

  2. Striation and convection in penumbral filaments

    Science.gov (United States)

    Spruit, H. C.; Scharmer, G. B.; Löfdahl, M. G.

    2010-10-01

    Observations with the 1-m Swedish Solar Telescope of the flows seen in penumbral filaments are presented. Time sequences of bright filaments show overturning motions strikingly similar to those seen along the walls of small isolated structures in the active regions. The filaments show outward propagating striations with inclination angles suggesting that they are aligned with the local magnetic field. We interpret it as the equivalent of the striations seen in the walls of small isolated magnetic structures. Their origin is then a corrugation of the boundary between an overturning convective flow inside the filament and the magnetic field wrapping around it. The outward propagation is a combination of a pattern motion due to the downflow observed along the sides of bright filaments, and the Evershed flow. The observed short wavelength of the striation argues against the existence of a dynamically significant horizontal field inside the bright filaments. Its intensity contrast is explained by the same physical effect that causes the dark cores of filaments, light bridges and “canals”. In this way striation represents an important clue to the physics of penumbral structure and its relation with other magnetic structures on the solar surface. We put this in perspective with results from the recent 3-D radiative hydrodynamic simulations. 4 movies are only available in electronic form at http://www.aanda.org

  3. Lifetime of titanium filament at constant current

    International Nuclear Information System (INIS)

    Chou, T.S.; Lanni, C.

    1981-01-01

    Titanium Sublimation Pump (TSP) represents the most efficient and the least expensive method to produce Ultra High Vacuum (UHV) in storage rings. In ISABELLE, a proton storage accelerator under construction at Brookhaven National Laboratory, for example, TSP provides a pumping speed for hydrogen of > 2 x 10 6 l/s. Due to the finite life of titanium filaments, new filaments have to be switched in before the end of filament burn out, to ensure smooth operation of the accelerator. Therefore, several operational modes that can be used to activate the TSP were studied. The constant current mode is a convenient way of maintaining constant evaporating rate by increasing the power input while the filament diameter decreases as titanium evaporates. The filaments used in this experiment were standard Varian 916-0024 filaments made of Ti 85%, Mo 15% alloy. During their lifetime at a constant current of 48 amperes, the evaporation rate rose to a maximum at about 10% of their life and then flattened out to a constant value, 0.25 g/hr. The maximum evaporation rate occurs coincidently with the recrystallization of 74% Ti 26% Mo 2 from microstructure crystalline at higher titanium concentration to macrostructure crystalline at lower titanium concentration. As the macrocrystal grows, the slip plane develops at the grain boundary resulting in high resistance at the slip plane which will eventually cause the filament burn out due to local heating

  4. Plasmid stability in dried cells of the desert cyanobacterium Chroococcidiopsis and its potential for GFP imaging of survivors on Earth and in space.

    Science.gov (United States)

    Billi, Daniela

    2012-06-01

    Two GFP-based plasmids, namely pTTQ18-GFP-pDU1(mini) and pDUCA7-GFP, of about 7 kbp and 15 kbp respectively, able to replicate in Chroococcidiopsis sp. CCMEE 029 and CCMEE 123, were developed. Both plasmids were maintained in Chroococcidiopsis cells after 18 months of dry storage as demonstrated by colony PCR, plasmid restriction analysis, GFP imaging and colony-forming ability under selection of dried transformants; thus suggesting that strategies employed by this cyanobacterium to stabilize dried chromosomal DNA, must have protected plasmid DNA. The suitability of pDU1(mini)-plasmid for GFP tagging in Chroococcidiopsis was investigated by using the RecA homolog of Synechocystis sp. PCC 6803. After 2 months of dry storage, the presence of dried cells with a GFP-RecA(Syn) distribution resembling that of hydrated cells, supported its capability of preventing desiccation-induced genome damage, whereas the rewetted cells with filamentous GFP-RecA(Syn) structures revealed sub-lethal DNA damage. The long-term stability of plasmid DNA in dried Chroococcidiopsis has implication for space research, for example when investigating the recovery of dried cells after Martian and space simulations or when developing life support systems based on phototrophs with genetically enhanced stress tolerance and stored in the dry state for prolonged periods.

  5. Thermal and Chemical Evolution of Collapsing Filaments

    Energy Technology Data Exchange (ETDEWEB)

    Gray, William J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Scannapieco, Evan [Arizona State Univ., Mesa, AZ (United States). School of Earth and Space Exploration

    2013-01-15

    Intergalactic filaments form the foundation of the cosmic web that connect galaxies together, and provide an important reservoir of gas for galaxy growth and accretion. Here we present very high resolution two-dimensional simulations of the thermal and chemical evolution of such filaments, making use of a 32 species chemistry network that tracks the evolution of key molecules formed from hydrogen, oxygen, and carbon. We study the evolution of filaments over a wide range of parameters including the initial density, initial temperature, strength of the dissociating UV background, and metallicity. In low-redshift, Z ≈ 0.1Z filaments, the evolution is determined completely by the initial cooling time. If this is sufficiently short, the center of the filament always collapses to form dense, cold core containing a substantial fraction of molecules. In high-redshift, Z = 10-3Z filaments, the collapse proceeds much more slowly. This is due mostly to the lower initial temperatures, which leads to a much more modest increase in density before the atomic cooling limit is reached, making subsequent molecular cooling much less efficient. Finally, we study how the gravitational potential from a nearby dwarf galaxy affects the collapse of the filament and compare this to NGC 5253, a nearby starbusting dwarf galaxy thought to be fueled by the accretion of filament gas. In contrast to our fiducial case, a substantial density peak forms at the center of the potential. This peak evolves faster than the rest of the filament due to the increased rate at which chemical species form and cooling occur. We find that we achieve similar accretion rates as NGC 5253, but our two-dimensional simulations do not recover the formation of the giant molecular clouds that are seen in radio observations.

  6. Filaments in simulations of molecular cloud formation

    Energy Technology Data Exchange (ETDEWEB)

    Gómez, Gilberto C.; Vázquez-Semadeni, Enrique [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, Campus Morelia Apartado Postal 3-72, 58090 Morelia, Michoacán (Mexico)

    2014-08-20

    We report on the filaments that develop self-consistently in a new numerical simulation of cloud formation by colliding flows. As in previous studies, the forming cloud begins to undergo gravitational collapse because it rapidly acquires a mass much larger than the average Jeans mass. Thus, the collapse soon becomes nearly pressureless, proceeding along its shortest dimension first. This naturally produces filaments in the cloud and clumps within the filaments. The filaments are not in equilibrium at any time, but instead are long-lived flow features through which the gas flows from the cloud to the clumps. The filaments are long-lived because they accrete from their environment while simultaneously accreting onto the clumps within them; they are essentially the locus where the flow changes from accreting in two dimensions to accreting in one dimension. Moreover, the clumps also exhibit a hierarchical nature: the gas in a filament flows onto a main, central clump but other, smaller-scale clumps form along the infalling gas. Correspondingly, the velocity along the filament exhibits a hierarchy of jumps at the locations of the clumps. Two prominent filaments in the simulation have lengths ∼15 pc and masses ∼600 M {sub ☉} above density n ∼ 10{sup 3} cm{sup –3} (∼2 × 10{sup 3} M {sub ☉} at n > 50 cm{sup –3}). The density profile exhibits a central flattened core of size ∼0.3 pc and an envelope that decays as r {sup –2.5} in reasonable agreement with observations. Accretion onto the filament reaches a maximum linear density rate of ∼30 M {sub ☉} Myr{sup –1} pc{sup –1}.

  7. Dried Colony in Cyanobacterium, Nostoc sp. HK-01 — Several high Space Environment Tolerances for ``Tanpopo'' Mission

    Science.gov (United States)

    Tomita-Yokotani, K.; Kimura, S.; Kimura, Y.; Igarashi, Y.; Ajioka, R.; Sato, S.; Katoh, H.; Baba, K.

    2013-11-01

    A cyanobacterium, Nostoc sp. HK-01, has high several space environmental tolerance. Nostoc sp HK-01 would have high contribution for the “Tanpopo” mission in Japan Experimental Module of the International Space Station.

  8. Mutation-specific effects on thin filament length in thin filament myopathy.

    Science.gov (United States)

    Winter, Josine M de; Joureau, Barbara; Lee, Eun-Jeong; Kiss, Balázs; Yuen, Michaela; Gupta, Vandana A; Pappas, Christopher T; Gregorio, Carol C; Stienen, Ger J M; Edvardson, Simon; Wallgren-Pettersson, Carina; Lehtokari, Vilma-Lotta; Pelin, Katarina; Malfatti, Edoardo; Romero, Norma B; Engelen, Baziel G van; Voermans, Nicol C; Donkervoort, Sandra; Bönnemann, C G; Clarke, Nigel F; Beggs, Alan H; Granzier, Henk; Ottenheijm, Coen A C

    2016-06-01

    Thin filament myopathies are among the most common nondystrophic congenital muscular disorders, and are caused by mutations in genes encoding proteins that are associated with the skeletal muscle thin filament. Mechanisms underlying muscle weakness are poorly understood, but might involve the length of the thin filament, an important determinant of force generation. We investigated the sarcomere length-dependence of force, a functional assay that provides insights into the contractile strength of muscle fibers as well as the length of the thin filaments, in muscle fibers from 51 patients with thin filament myopathy caused by mutations in NEB, ACTA1, TPM2, TPM3, TNNT1, KBTBD13, KLHL40, and KLHL41. Lower force generation was observed in muscle fibers from patients of all genotypes. In a subset of patients who harbor mutations in NEB and ACTA1, the lower force was associated with downward shifted force-sarcomere length relations, indicative of shorter thin filaments. Confocal microscopy confirmed shorter thin filaments in muscle fibers of these patients. A conditional Neb knockout mouse model, which recapitulates thin filament myopathy, revealed a compensatory mechanism; the lower force generation that was associated with shorter thin filaments was compensated for by increasing the number of sarcomeres in series. This allowed muscle fibers to operate at a shorter sarcomere length and maintain optimal thin-thick filament overlap. These findings might provide a novel direction for the development of therapeutic strategies for thin filament myopathy patients with shortened thin filament lengths. Ann Neurol 2016;79:959-969. © 2016 American Neurological Association.

  9. Filament poisoning at typical carbon nanotube deposition conditions by hot-filament CVD

    CSIR Research Space (South Africa)

    Oliphant, CJ

    2009-05-01

    Full Text Available extensively used for the deposition of various materials, including diamond [1], polymers [2], silicon thin films [3], boron-carbon-nitride layers [4] and carbon nanotubes (CNTs) [5]. The process relies on the catalytic decomposition of precursor gases... (Ho) twice as efficient as a W filament during the deposition of microcrystalline silicon thin films [6]. Reactions between the precursor gases and the heated filament result in changes of the structural properties of the filaments; a process...

  10. Intense EM filamentation in relativistic hot plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Qiang-Lin [Department of Physics, Jinggangshan University, Ji' an, Jiangxi 343009 (China); Chen, Zhong-Ping [Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, Austin, TX 78712 (United States); Mahajan, Swadesh M., E-mail: mahajan@mail.utexas.edu [Department of Physics and Institute for Fusion Studies, The University of Texas at Austin, Austin, TX 78712 (United States); Department of Physics, School of Natural Sciences, Shiv Nadar University, Uttar Pradesh 201314 (India)

    2017-03-03

    Highlights: • Breaking up of an intense EM pulse into filaments is a spectacular demonstration of the nonlinear wave-plasma interaction. • Filaments are spectacularly sharper, highly extended and longer lived at relativistic temperatures. • EM energy concentration can trigger new nonlinear phenomena with absolute consequences for high energy density matter. - Abstract: Through 2D particle-in-cell (PIC) simulations, we demonstrate that the nature of filamentation of a high intensity electromagnetic (EM) pulse propagating in an underdense plasma, is profoundly affected at relativistically high temperatures. The “relativistic” filaments are sharper, are dramatically extended (along the direction of propagation), and live much longer than their lower temperature counterparts. The thermally boosted electron inertia is invoked to understand this very interesting and powerful phenomenon.

  11. Morgellons disease: a filamentous borrelial dermatitis

    OpenAIRE

    Middelveen, Marianne J; Stricker, Raphael B

    2016-01-01

    Marianne J Middelveen, Raphael B Stricker International Lyme and Associated Diseases Society, Bethesda, MD, USA Abstract: Morgellons disease (MD) is a dermopathy characterized by multicolored filaments that lie under, are embedded in, or project from skin. Although MD was initially considered to be a delusional disorder, recent studies have demonstrated that the dermopathy is associated with tickborne infection, that the filaments are composed of keratin and collagen, and that they resu...

  12. Control of multiple filamentation in air

    Science.gov (United States)

    Fibich, Gadi; Eisenmann, Shmuel; Ilan, Boaz; Zigler, Arie

    2004-08-01

    In this Letter we provide what is believed to be the first experimental evidence of suppression of the number of filaments for high-intensity laser pulses propagating in air by beam astigmatism. We also show that the number, pattern, and spatial stability of the filaments can be controlled by varying the angle that a focusing lens makes with the axial direction of propagation. This new methodology can be useful for applications involving atmospheric propagation, such as remote sensing.

  13. Flux Cancellation Leading to CME Filament Eruptions

    Science.gov (United States)

    Popescu, Roxana M.; Panesar, Navdeep K.; Sterling, Alphonse C.; Moore, Ronald L.

    2016-01-01

    Solar filaments are strands of relatively cool, dense plasma magnetically suspended in the lower density hotter solar corona. They trace magnetic polarity inversion lines (PILs) in the photosphere below, and are supported against gravity at heights of up to approx.100 Mm above the chromosphere by the magnetic field in and around them. This field erupts when it is rendered unstable, often by magnetic flux cancellation or emergence at or near the PIL. We have studied the evolution of photospheric magnetic flux leading to ten observed filament eruptions. Specifically, we look for gradual magnetic changes in the neighborhood of the PIL prior to and during eruption. We use Extreme Ultraviolet (EUV) images from the Atmospheric Imaging Assembly (AIA), and magnetograms from the Helioseismic and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO), to study filament eruptions and their photospheric magnetic fields. We examine whether flux cancellation or/and emergence leads to filament eruptions. We find that continuous flux cancellation was present at the PIL for many hours prior to each eruption. We present two CME-producing eruptions in detail and find the following: (a) the pre-eruption filament-holding core field is highly sheared and appears in the shape of a sigmoid above the PIL; (b) at the start of the eruption the opposite arms of the sigmoid reconnect in the middle above the site of (tether-cutting) flux cancellation at the PIL; (c) the filaments first show a slow-rise, followed by a fast-rise as they erupt. We conclude that these two filament eruptions result from flux cancellation in the middle of the sheared field, and thereafter evolve in agreement with the standard model for a CME/flare filament eruption from a closed bipolar magnetic field [flux cancellation (van Ballegooijen and Martens 1989 and Moore and Roumelrotis 1992) and runaway tether-cutting (Moore et. al 2001)].

  14. Can we determine the filament chirality by the filament footpoint location or the barb-bearing?

    Science.gov (United States)

    Hao, Qi; Guo, Yang; Fang, Cheng; Chen, Peng-Fei; Cao, Wen-Da

    2016-01-01

    We attempt to propose a method for automatically detecting the solar filament chirality and barb bearing. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm to recognize the filament spine. Then, we use the polarity inversion line (PIL) shift method for measuring the polarities on both sides of the filament, and employ the connected components labeling method to identify the barbs and calculate the angle between each barb and the spine to determine the bearing of the barbs, i.e., left or right. We test the automatic detection method with Hα filtergrams from the Big Bear Solar Observatory (BBSO) Hα archive and magnetograms observed with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Four filaments are automatically detected and illustrated to show the results. The barbs in different parts of a filament may have opposite bearings. The filaments in the southern hemisphere (northern hemisphere) mainly have left-bearing (right-bearing) barbs and positive (negative) magnetic helicity, respectively. The tested results demonstrate that our method is efficient and effective in detecting the bearing of filament barbs. It is demonstrated that the conventionally believed one-to-one correspondence between filament chirality and barb bearing is not valid. The correct detection of the filament axis chirality should be done by combining both imaging morphology and magnetic field observations.

  15. Can we determine the filament chirality by the filament footpoint location or the barb-bearing?

    International Nuclear Information System (INIS)

    Hao, Qi; Guo, Yang; Fang, Cheng; Chen, Peng-Fei; Cao, Wen-Da

    2016-01-01

    We attempt to propose a method for automatically detecting the solar filament chirality and barb bearing. We first introduce the concept of an unweighted undirected graph and adopt the Dijkstra shortest path algorithm to recognize the filament spine. Then, we use the polarity inversion line (PIL) shift method for measuring the polarities on both sides of the filament, and employ the connected components labeling method to identify the barbs and calculate the angle between each barb and the spine to determine the bearing of the barbs, i.e., left or right. We test the automatic detection method with Hα filtergrams from the Big Bear Solar Observatory (BBSO) Hα archive and magnetograms observed with the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). Four filaments are automatically detected and illustrated to show the results. The barbs in different parts of a filament may have opposite bearings. The filaments in the southern hemisphere (northern hemisphere) mainly have left-bearing (right-bearing) barbs and positive (negative) magnetic helicity, respectively. The tested results demonstrate that our method is efficient and effective in detecting the bearing of filament barbs. It is demonstrated that the conventionally believed one-to-one correspondence between filament chirality and barb bearing is not valid. The correct detection of the filament axis chirality should be done by combining both imaging morphology and magnetic field observations. (paper)

  16. Dimensional quantization effects in the thermodynamics of conductive filaments

    Science.gov (United States)

    Niraula, D.; Grice, C. R.; Karpov, V. G.

    2018-06-01

    We consider the physical effects of dimensional quantization in conductive filaments that underlie operations of some modern electronic devices. We show that, as a result of quantization, a sufficiently thin filament acquires a positive charge. Several applications of this finding include the host material polarization, the stability of filament constrictions, the equilibrium filament radius, polarity in device switching, and quantization of conductance.

  17. Evidence for Mixed Helicity in Erupting Filaments

    Science.gov (United States)

    Muglach, K.; Wang, Y.-M.; Kliem, B.

    2009-09-01

    Erupting filaments are sometimes observed to undergo a rotation about the vertical direction as they rise. This rotation of the filament axis is generally interpreted as a conversion of twist into writhe in a kink-unstable magnetic flux rope. Consistent with this interpretation, the rotation is usually found to be clockwise (as viewed from above) if the post-eruption arcade has right-handed helicity, but counterclockwise if it has left-handed helicity. Here, we describe two non-active-region filament events recorded with the Extreme-Ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory in which the sense of rotation appears to be opposite to that expected from the helicity of the post-event arcade. Based on these observations, we suggest that the rotation of the filament axis is, in general, determined by the net helicity of the erupting system, and that the axially aligned core of the filament can have the opposite helicity sign to the surrounding field. In most cases, the surrounding field provides the main contribution to the net helicity. In the events reported here, however, the helicity associated with the filament "barbs" is opposite in sign to and dominates that of the overlying arcade.

  18. Energy transfer in Anabaena variabilis filaments adapted to nitrogen-depleted and nitrogen-enriched conditions studied by time-resolved fluorescence.

    Science.gov (United States)

    Onishi, Aya; Aikawa, Shimpei; Kondo, Akihiko; Akimoto, Seiji

    2017-09-01

    Nitrogen is among the most important nutritious elements for photosynthetic organisms such as plants, algae, and cyanobacteria. Therefore, nitrogen depletion severely compromises the growth, development, and photosynthesis of these organisms. To preserve their integrity under nitrogen-depleted conditions, filamentous nitrogen-fixing cyanobacteria reduce atmospheric nitrogen to ammonia, and self-adapt by regulating their light-harvesting and excitation energy-transfer processes. To investigate the changes in the primary processes of photosynthesis, we measured the steady-state absorption and fluorescence spectra and time-resolved fluorescence spectra (TRFS) of whole filaments of the nitrogen-fixing cyanobacterium Anabaena variabilis at 77 K. The filaments were grown in standard and nitrogen-free media for 6 months. The TRFS were measured with a picosecond time-correlated single photon counting system. Despite the phycobilisome degradation, the energy-transfer paths within phycobilisome and from phycobilisome to both photosystems were maintained. However, the energy transfer from photosystem II to photosystem I was suppressed and a specific red chlorophyll band appeared under the nitrogen-depleted condition.

  19. Genetic manipulation of a metabolic enzyme and a transcriptional regulator increasing succinate excretion from unicellular cyanobacterium

    Directory of Open Access Journals (Sweden)

    Takashi eOsanai

    2015-10-01

    Full Text Available Succinate is a building block compound that the U.S. Department of Energy has declared as important in biorefineries, and it is widely used as a commodity chemical. Here, we identified the two genes increasing succinate production of the unicellular cyanobacterium Synechocystis sp. PCC 6803. Succinate was excreted under dark, anaerobic conditions, and its production level increased by knocking out ackA, which encodes an acetate kinase, and by overexpressing sigE, which encodes an RNA polymerase sigma factor. Glycogen catabolism and organic acid biosynthesis were enhanced in the mutant lacking ackA and overexpressing sigE, leading to an increase in succinate production reaching 5 times of the wild-type levels. Our genetic and metabolomic analyses thus demonstrated the effect of genetic manipulation of a metabolic enzyme and a transcriptional regulator on succinate excretion from this cyanobacterium with the data based on metabolomic technique.

  20. Lack of Methylated Hopanoids Renders the Cyanobacterium Nostoc punctiforme Sensitive to Osmotic and pH Stress.

    Science.gov (United States)

    Garby, Tamsyn J; Matys, Emily D; Ongley, Sarah E; Salih, Anya; Larkum, Anthony W D; Walter, Malcolm R; Summons, Roger E; Neilan, Brett A

    2017-07-01

    To investigate the function of 2-methylhopanoids in modern cyanobacteria, the hpnP gene coding for the radical S -adenosyl methionine (SAM) methylase protein that acts on the C-2 position of hopanoids was deleted from the filamentous cyanobacterium Nostoc punctiforme ATCC 29133S. The resulting Δ hpnP mutant lacked all 2-methylhopanoids but was found to produce much higher levels of two bacteriohopanepentol isomers than the wild type. Growth rates of the Δ hpnP mutant cultures were not significantly different from those of the wild type under standard growth conditions. Akinete formation was also not impeded by the absence of 2-methylhopanoids. The relative abundances of the different hopanoid structures in akinete-dominated cultures of the wild-type and Δ hpnP mutant strains were similar to those of vegetative cell-dominated cultures. However, the Δ hpnP mutant was found to have decreased growth rates under both pH and osmotic stress, confirming a role for 2-methylhopanoids in stress tolerance. Evidence of elevated photosystem II yield and NAD(P)H-dependent oxidoreductase activity in the Δ hpnP mutant under stress conditions, compared to the wild type, suggested that the absence of 2-methylhopanoids increases cellular metabolic rates under stress conditions. IMPORTANCE As the first group of organisms to develop oxygenic photosynthesis, Cyanobacteria are central to the evolutionary history of life on Earth and the subsequent oxygenation of the atmosphere. To investigate the origin of cyanobacteria and the emergence of oxygenic photosynthesis, geobiologists use biomarkers, the remnants of lipids produced by different organisms that are found in geologic sediments. 2-Methylhopanes have been considered indicative of cyanobacteria in some environmental settings, with the parent lipids 2-methylhopanoids being present in many contemporary cyanobacteria. We have created a Nostoc punctiforme Δ hpnP mutant strain that does not produce 2-methylhopanoids to assess the

  1. A new UV-A/B protecting pigment in the terrestrial cyanobacterium Nostoc commune

    International Nuclear Information System (INIS)

    Scherer, S.; Chen, T.W.; Boeger, P.

    1988-01-01

    A new ultraviolet (UV)-A/B absorbing pigment with maxima at 312 and 330 nanometers from the cosmopolitan terrestrial cyanobacterium Nostoc commune is described. The pigment is found in high amounts (up to 10% of dry weight) in colonies grown under solar UV radiation but only in low concentrations in laboratory cultures illuminated by artificial light without UV. Its experimental induction by UV as well as its capacity to efficiently protect Nostoc against UV radiation is reported

  2. A new endonuclease recognizing the deoxynucleotide sequence CCNNGG from the cyanobacterium Synechocystis 6701.

    Science.gov (United States)

    Calléja, F; Tandeau de Marsac, N; Coursin, T; van Ormondt, H; de Waard, A

    1985-09-25

    A new sequence-specific endonuclease from the cyanobacterium Synechocystis species PCC 6701 has been purified and characterized. This enzyme, SecI, is unique in recognizing the nucleotide sequence: 5' -CCNNGG-3' 3' -GGNNCC-5' and cleaves it at the position indicated by the symbol. Two other restriction endonucleases, SecII and SecIII, found in this organism are isoschizomers of MspI and MstII, respectively.

  3. CyanOmics: an integrated database of omics for the model cyanobacterium Synechococcus sp. PCC 7002

    OpenAIRE

    Yang, Yaohua; Feng, Jie; Li, Tao; Ge, Feng; Zhao, Jindong

    2015-01-01

    Cyanobacteria are an important group of organisms that carry out oxygenic photosynthesis and play vital roles in both the carbon and nitrogen cycles of the Earth. The annotated genome of Synechococcus sp. PCC 7002, as an ideal model cyanobacterium, is available. A series of transcriptomic and proteomic studies of Synechococcus sp. PCC 7002 cells grown under different conditions have been reported. However, no database of such integrated omics studies has been constructed. Here we present Cyan...

  4. Terahertz waves radiated from two noncollinear femtosecond plasma filaments

    Energy Technology Data Exchange (ETDEWEB)

    Du, Hai-Wei; Hoshina, Hiromichi; Otani, Chiko, E-mail: otani@riken.jp [Terahertz Sensing and Imaging Research Team, RIKEN Center for Advanced Photonics, RIKEN, Sendai, Miyagi 980-0845 (Japan); Midorikawa, Katsumi [Attosecond Science Research Team, RIKEN Center for Advanced Photonics, RIKEN, Wako, Saitama 351-0198 (Japan)

    2015-11-23

    Terahertz (THz) waves radiated from two noncollinear femtosecond plasma filaments with a crossing angle of 25° are investigated. The irradiated THz waves from the crossing filaments show a small THz pulse after the main THz pulse, which was not observed in those from single-filament scheme. Since the position of the small THz pulse changes with the time-delay of two filaments, this phenomenon can be explained by a model in which the small THz pulse is from the second filament. The denser plasma in the overlap region of the filaments changes the movement of space charges in the plasma, thereby changing the angular distribution of THz radiation. As a result, this schematic induces some THz wave from the second filament to propagate along the path of the THz wave from the first filament. Thus, this schematic alters the direction of the THz radiation from the filamentation, which can be used in THz wave remote sensing.

  5. Heterologous expression of cellobiohydrolases in filamentous fungi

    DEFF Research Database (Denmark)

    Zoglowek, Marta; Lübeck, Peter S.; Ahring, Birgitte K.

    2015-01-01

    Cellobiohydrolases are among the most important enzymes functioning in the hydrolysis of crystalline cellulose, significantly contributing to the efficient biorefining of recalcitrant lignocellulosic biomass into biofuels and bio-based products. Filamentous fungi are recognized as both well...... into valuable products. However, due to low cellobiohydrolase activities, certain fungi might be deficient with regard to enzymes of value for cellulose conversion, and improving cellobiohydrolase expression in filamentous fungi has proven to be challenging. In this review, we examine the effects of altering...... promoters, signal peptides, culture conditions and host post-translational modifications. For heterologous cellobiohydrolase production in filamentous fungi to become an industrially feasible process, the construction of site-integrating plasmids, development of protease-deficient strains and glycosylation...

  6. Intermediate filaments and gene regulation.

    Science.gov (United States)

    Traub, P

    1995-01-01

    The biological role of intermediate filaments (IFs) of eukaryotic cells is still a matter of conjecture. On the basis of immunofluorescence and electron microscopic observations, they appear to play a cytoskeletal role in that they stabilize cellular structure and organize the distribution and interactions of intracellular organelles and components. The expression of a large number of cell type-specific and developmentally regulated subunit proteins is believed to provide multicellular organisms with different IF systems capable of differential interactions with the various substructures and components of their multiple, differentiated cells. However, the destruction of distinct IF systems by manipulation of cultured cells or by knock-out mutation of IF subunit proteins in transgenic mice exerts relatively little influence on cellular morphology and physiology and on development of mutant animals. In order to rationalize this dilemma, the cytoskeletal concept of IF function has been extended to purport that cytoplasmic (c) IFs and their subunit proteins also play fundamental roles in gene regulation. It is based on the in vitro capacity of cIF(protein)s to interact with guanine-rich, single-stranded DNA, supercoiled DNA and histones, as well as on their close structural relatedness to gene-regulatory DNA-binding and nuclear matrix proteins. Since cIF proteins do not possess classical nuclear localization signals, it is proposed that cIFs directly penetrate the double nuclear membrane, exploiting the amphiphilic, membrane-active character of their subunit proteins. Since they can establish metastable multisite contacts with nuclear matrix structures and/or chromatin areas containing highly repetitive DNA sequence elements at the nuclear periphery, they are supposed to participate in chromosome distribution and chromatin organization in interphase nuclei of differentiated cells. Owing to their different DNA-binding specificities, the various cIF systems may in this

  7. Heterologous gene expression in filamentous fungi.

    Science.gov (United States)

    Su, Xiaoyun; Schmitz, George; Zhang, Meiling; Mackie, Roderick I; Cann, Isaac K O

    2012-01-01

    Filamentous fungi are critical to production of many commercial enzymes and organic compounds. Fungal-based systems have several advantages over bacterial-based systems for protein production because high-level secretion of enzymes is a common trait of their decomposer lifestyle. Furthermore, in the large-scale production of recombinant proteins of eukaryotic origin, the filamentous fungi become the vehicle of choice due to critical processes shared in gene expression with other eukaryotic organisms. The complexity and relative dearth of understanding of the physiology of filamentous fungi, compared to bacteria, have hindered rapid development of these organisms as highly efficient factories for the production of heterologous proteins. In this review, we highlight several of the known benefits and challenges in using filamentous fungi (particularly Aspergillus spp., Trichoderma reesei, and Neurospora crassa) for the production of proteins, especially heterologous, nonfungal enzymes. We review various techniques commonly employed in recombinant protein production in the filamentous fungi, including transformation methods, selection of gene regulatory elements such as promoters, protein secretion factors such as the signal peptide, and optimization of coding sequence. We provide insights into current models of host genomic defenses such as repeat-induced point mutation and quelling. Furthermore, we examine the regulatory effects of transcript sequences, including introns and untranslated regions, pre-mRNA (messenger RNA) processing, transcript transport, and mRNA stability. We anticipate that this review will become a resource for researchers who aim at advancing the use of these fascinating organisms as protein production factories, for both academic and industrial purposes, and also for scientists with general interest in the biology of the filamentous fungi. Copyright © 2012 Elsevier Inc. All rights reserved.

  8. Mechanical model for filament buckling and growth by phase ordering.

    Science.gov (United States)

    Rey, Alejandro D; Abukhdeir, Nasser M

    2008-02-05

    A mechanical model of open filament shape and growth driven by phase ordering is formulated. For a given phase-ordering driving force, the model output is the filament shape evolution and the filament end-point kinematics. The linearized model for the slope of the filament is the Cahn-Hilliard model of spinodal decomposition, where the buckling corresponds to concentration fluctuations. Two modes are predicted: (i) sequential growth and buckling and (ii) simultaneous buckling and growth. The relation among the maximum buckling rate, filament tension, and matrix viscosity is given. These results contribute to ongoing work in smectic A filament buckling.

  9. Filament stretching rheometer: inertia compensation revisited

    DEFF Research Database (Denmark)

    Szabo, Peter; McKinley, Gareth H.

    2003-01-01

    The necessary inertia compensation used in the force balance for the filament stretching rheometer is derived for an arbitrary frame of reference. This enables the force balance to be used to extract correctly the extensional viscosity from measurements of the tensile force at either end of the e......The necessary inertia compensation used in the force balance for the filament stretching rheometer is derived for an arbitrary frame of reference. This enables the force balance to be used to extract correctly the extensional viscosity from measurements of the tensile force at either end...

  10. Infrared Radiation Filament And Metnod Of Manufacture

    Science.gov (United States)

    Johnson, Edward A.

    1998-11-17

    An improved IR radiation source is provided by the invention. A radiation filament has a textured surface produced by seeded ion bombardment of a metal foil which is cut to a serpentine shape and mounted in a windowed housing. Specific ion bombardment texturing techniques tune the surface to maximize emissions in the desired wavelength range and to limit emissions outside that narrow range, particularly at longer wavelengths. A combination of filament surface texture, thickness, material, shape and power circuit feedback control produce wavelength controlled and efficient radiation at much lower power requirements than devices of the prior art.

  11. Analytical Core Mass Function (CMF) from Filaments: Under Which Circumstances Can Filament Fragmentation Reproduce the CMF?

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yueh-Ning; Hennebelle, Patrick [IRFU, CEA, Université Paris-Saclay, F-91191 Gif-sur-Yvette (France); Chabrier, Gilles, E-mail: yueh-ning.lee@cea.fr [École normale supérieure de Lyon, CRAL, UMR CNRS 5574, Université de Lyon, F-69364 Lyon Cedex 07 (France)

    2017-10-01

    Observations suggest that star formation in filamentary molecular clouds occurs in a two-step process, with the formation of filaments preceding that of prestellar cores and stars. Here, we apply the gravoturbulent fragmentation theory of Hennebelle and Chabrier to a filamentary environment, taking into account magnetic support. We discuss the induced geometrical effect on the cores, with a transition from 3D geometry at small scales to 1D at large ones. The model predicts the fragmentation behavior of a filament for a given mass per unit length (MpL) and level of magnetization. This core mass function (CMF) for individual filaments is then convolved with the distribution of filaments to obtain the final system CMF. The model yields two major results. (i) The filamentary geometry naturally induces a hierarchical fragmentation process, first into groups of cores, separated by a length equal to a few filament Jeans lengths, i.e., a few times the filament width. These groups then fragment into individual cores. (ii) Non-magnetized filaments with high MpL are found to fragment excessively, at odds with observations. This is resolved by taking into account the magnetic field (treated simply as additional pressure support). The present theory suggests two complementary modes of star formation: although small (spherical or filamentary) structures will collapse directly into prestellar cores, according to the standard Hennebelle–Chabrier theory, the large (filamentary) ones, the dominant population according to observations, will follow the aforedescribed two-step process.

  12. Myosin binding protein-C activates thin filaments and inhibits thick filaments in heart muscle cells.

    Science.gov (United States)

    Kampourakis, Thomas; Yan, Ziqian; Gautel, Mathias; Sun, Yin-Biao; Irving, Malcolm

    2014-12-30

    Myosin binding protein-C (MyBP-C) is a key regulatory protein in heart muscle, and mutations in the MYBPC3 gene are frequently associated with cardiomyopathy. However, the mechanism of action of MyBP-C remains poorly understood, and both activating and inhibitory effects of MyBP-C on contractility have been reported. To clarify the function of the regulatory N-terminal domains of MyBP-C, we determined their effects on the structure of thick (myosin-containing) and thin (actin-containing) filaments in intact sarcomeres of heart muscle. We used fluorescent probes on troponin C in the thin filaments and on myosin regulatory light chain in the thick filaments to monitor structural changes associated with activation of demembranated trabeculae from rat ventricle by the C1mC2 region of rat MyBP-C. C1mC2 induced larger structural changes in thin filaments than calcium activation, and these were still present when active force was blocked with blebbistatin, showing that C1mC2 directly activates the thin filaments. In contrast, structural changes in thick filaments induced by C1mC2 were smaller than those associated with calcium activation and were abolished or reversed by blebbistatin. Low concentrations of C1mC2 did not affect resting force but increased calcium sensitivity and reduced cooperativity of force and structural changes in both thin and thick filaments. These results show that the N-terminal region of MyBP-C stabilizes the ON state of thin filaments and the OFF state of thick filaments and lead to a novel hypothesis for the physiological role of MyBP-C in the regulation of cardiac contractility.

  13. High-resolution Observations of Sympathetic Filament Eruptions by NVST

    Energy Technology Data Exchange (ETDEWEB)

    Li, Shangwei; Su, Yingna; Zhou, Tuanhui; Ji, Haisheng [Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, CAS, Nanjing 210008 (China); Van Ballegooijen, Adriaan [5001 Riverwood Avenue, Sarasota, FL 34231 (United States); Sun, Xudong, E-mail: ynsu@pmo.ac.cn [W. W. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

    2017-07-20

    We investigate two sympathetic filament eruptions observed by the New Vacuum Solar Telescope on 2015 October 15. The full picture of the eruptions is obtained from the corresponding Solar Dynamics Observatory ( SDO )/Atmospheric Imaging Assembly (AIA) observations. The two filaments start from active region NOAA 12434 in the north and end in one large quiescent filament channel in the south. The left filament erupts first, followed by the right filament eruption about 10 minutes later. Clear twist structure and rotating motion are observed in both filaments during the eruption. Both eruptions failed, since the filaments first rise up, then flow toward the south and merge into the southern large quiescent filament. We also observe repeated activations of mini filaments below the right filament after its eruption. Using magnetic field models constructed based on SDO /HMI magnetograms via the flux rope insertion method, we find that the left filament eruption is likely to be triggered by kink instability, while the weakening of overlying magnetic fields due to magnetic reconnection at an X-point between the two filament systems might play an important role in the onset of the right filament eruption.

  14. The exo-metabolome in filamentous fungi

    DEFF Research Database (Denmark)

    Thrane, Ulf; Andersen, Birgitte; Frisvad, Jens Christian

    2007-01-01

    Filamentous fungi are a diverse group of eukaryotic microorganisms that have a significant impact on human life as spoilers of food and feed by degradation and toxin production. They are also most useful as a source of bulk and fine chemicals and pharmaceuticals. This chapter focuses on the exo-metabolome...

  15. Nonlinear Binormal Flow of Vortex Filaments

    Science.gov (United States)

    Strong, Scott; Carr, Lincoln

    2015-11-01

    With the current advances in vortex imaging of Bose-Einstein condensates occurring at the Universities of Arizona, São Paulo and Cambridge, interest in vortex filament dynamics is experiencing a resurgence. Recent simulations, Salman (2013), depict dissipative mechanisms resulting from vortex ring emissions and Kelvin wave generation associated with vortex self-intersections. As the local induction approximation fails to capture reconnection events, it lacks a similar dissipative mechanism. On the other hand, Strong&Carr (2012) showed that the exact representation of the velocity field induced by a curved segment of vortex contains higher-order corrections expressed in powers of curvature. This nonlinear binormal flow can be transformed, Hasimoto (1972), into a fully nonlinear equation of Schrödinger type. Continued transformation, Madelung (1926), reveals that the filament's square curvature obeys a quasilinear scalar conservation law with source term. This implies a broader range of filament dynamics than is possible with the integrable linear binormal flow. In this talk we show the affect higher-order corrections have on filament dynamics and discuss physical scales for which they may be witnessed in future experiments. Partially supported by NSF.

  16. On viscoelastic instability in polymeric filaments

    DEFF Research Database (Denmark)

    Rasmussen, Henrik Koblitz; Hassager, Ole

    1999-01-01

    The 3D Lagrangian Integral Method is used to simulate the effects of surface tension on the viscoelastic end-plate instability, occuring in the rapid extension of some polymeric filaments between parallel plates. It is shovn that the surface tension delays the onset of the instability. Furthermore...

  17. Modelling the morphology of filamentous microorganisms

    DEFF Research Database (Denmark)

    Nielsen, Jens Bredal

    1996-01-01

    The rapid development in image analysis techniques has made it possible to study the growth kinetics of filamentous microorganisms in more detail than previously, However, owing to the many different processes that influence the morphology it is important to apply mathematical models to extract...

  18. Filamentous bacteria transport electrons over centimetre distances

    DEFF Research Database (Denmark)

    Pfeffer, Christian; Larsen, Steffen; Song, Jie

    2012-01-01

    across centimetre-wide zones. Here we present evidence that the native conductors are long, filamentous bacteria. They abounded in sediment zones with electric currents and along their length they contained strings with distinct properties in accordance with a function as electron transporters. Living...

  19. Ponderomotive and thermal filamentation of laser light

    International Nuclear Information System (INIS)

    Kruer, W.L.

    1985-01-01

    As targets are irradiated with longer, more energetic pulses of laser light, longer-scalelength plasmas are produced. Filamentation is a potentially important process in such plasmas. In this instability, perturbations in the intensity profile of an incident light beam grow in amplitude, causing the beam to break up into intense filaments. The instability arises when a local increase in the light intensity creates a depression in plasma density either directly, via the ponderomotive force, or indirectly, via enhanced collisional absorption and subsequent plasma expansion. The density depression refracts the light into the lower-density region, enhancing the intensity perturbations. The instability is termed either ponderomotive or thermal filamentation, depending on which mechanism generates the density depression. The analogous process involving the entire beam is called self-focusing. Filamentation can significantly affect laser-plasma coupling. Intensity enhancements can introduce or modify other instabilities, change the location of the energy deposition, and possibly aggravate deleterious collective effects such as hot-electron generation

  20. Solar Filaments as Tracers of Subsurface Processes

    Indian Academy of Sciences (India)

    tribpo

    and filament eruptions, then, one might hope to discover important properties of the .... reasoning would lead to an estimated average field of 23 G in the corona, in ... paradigm relies heavily on the concept of twisted flux ropes as agents of ...

  1. Large-scale Motion of Solar Filaments

    Indian Academy of Sciences (India)

    tribpo

    Large-scale Motion of Solar Filaments. Pavel Ambrož, Astronomical Institute of the Acad. Sci. of the Czech Republic, CZ-25165. Ondrejov, The Czech Republic. e-mail: pambroz@asu.cas.cz. Alfred Schroll, Kanzelhöehe Solar Observatory of the University of Graz, A-9521 Treffen,. Austria. e-mail: schroll@solobskh.ac.at.

  2. Evolution of genetic systems in filamentous ascomycetes

    NARCIS (Netherlands)

    Nauta, M.J.

    1994-01-01

    A great variety of genetic systems exist in filamentous ascomycetes. The transmission of genetic material does not only occur by (sexual or asexual) reproduction, but it can also follow vegetative fusion of different strains. In this thesis the evolution of this variability is studied,

  3. Morphology and rheology in filamentous cultivations.

    Science.gov (United States)

    Wucherpfennig, T; Kiep, K A; Driouch, H; Wittmann, C; Krull, R

    2010-01-01

    Because of their metabolic diversity, high production capacity, secretion efficiency, and capability of carrying out posttranslational modifications, filamentous fungi are widely exploited as efficient cell factories in the production of metabolites, bioactive substances, and native or heterologous proteins, respectively. There is, however, a complex relationship between the morphology of these microorganisms, transport phenomena, the viscosity of the cultivation broth, and related productivity. The morphological characteristics vary between freely dispersed mycelia and distinct pellets of aggregated biomass, every growth form having a distinct influence on broth rheology. Hence, the advantages and disadvantages for mycelial or pellet cultivation have to be balanced out carefully. Because of the still inadequate understanding of the morphogenesis of filamentous microorganisms, fungal morphology is often a bottleneck of productivity in industrial production. To obtain an optimized production process, it is of great importance to gain a better understanding of the molecular and cell biology of these microorganisms as well as the relevant approaches in biochemical engineering. In this chapter, morphology and growth of filamentous fungi are described, with special attention given to specific problems as they arise from fungal growth forms; growth and mass transfer in fungal biopellets are discussed as an example. To emphasize the importance of the flow behavior of filamentous cultivation broths, an introduction to rheology is also given, reviewing important rheological models and recent studies concerning rheological parameters. Furthermore, current knowledge on morphology and productivity in relation to the environom is outlined in the last section of this review. Copyright 2010 Elsevier Inc. All rights reserved.

  4. A symplectic integration method for elastic filaments

    Science.gov (United States)

    Ladd, Tony; Misra, Gaurav

    2009-03-01

    Elastic rods are a ubiquitous coarse-grained model of semi-flexible biopolymers such as DNA, actin, and microtubules. The Worm-Like Chain (WLC) is the standard numerical model for semi-flexible polymers, but it is only a linearized approximation to the dynamics of an elastic rod, valid for small deflections; typically the torsional motion is neglected as well. In the standard finite-difference and finite-element formulations of an elastic rod, the continuum equations of motion are discretized in space and time, but it is then difficult to ensure that the Hamiltonian structure of the exact equations is preserved. Here we discretize the Hamiltonian itself, expressed as a line integral over the contour of the filament. This discrete representation of the continuum filament can then be integrated by one of the explicit symplectic integrators frequently used in molecular dynamics. The model systematically approximates the continuum partial differential equations, but has the same level of computational complexity as molecular dynamics and is constraint free. Numerical tests show that the algorithm is much more stable than a finite-difference formulation and can be used for high aspect ratio filaments, such as actin. We present numerical results for the deterministic and stochastic motion of single filaments.

  5. Filament Channel Formation, Eruption, and Jet Generation

    Science.gov (United States)

    DeVore, C. Richard; Antiochos, Spiro K.; Karpen, Judith T.

    2017-08-01

    The mechanism behind filament-channel formation is a longstanding mystery, while that underlying the initiation of coronal mass ejections and jets has been studied intensively but is not yet firmly established. In previous work, we and collaborators have investigated separately the consequences of magnetic-helicity condensation (Antiochos 2013) for forming filament channels (Zhao et al. 2015; Knizhnik et al. 2015, 2017a,b) and of the embedded-bipole model (Antiochos 1996) for generating reconnection-driven jets (Pariat et al. 2009, 2010, 2015, 2016; Wyper et al. 2016, 2017). Now we have taken a first step toward synthesizing these two lines of investigation. Our recent study (Karpen et al. 2017) of coronal-hole jets with gravity and wind employed an ad hoc, large-scale shear flow at the surface to introduce magnetic free energy and form the filament channel. In this effort, we replace the shear flow with an ensemble of local rotation cells, to emulate the Sun’s ever-changing granules and supergranules. As in our previous studies, we find that reconnection between twisted flux tubes within the closed-field region concentrates magnetic shear and free energy near the polarity inversion line, forming the filament channel. Onset of reconnection between this field and the external, unsheared, open field releases stored energy to drive the impulsive jet. We discuss the results of our new simulations with implications for understanding solar activity and space weather.

  6. Filament stretching rheometry of polymer melts

    DEFF Research Database (Denmark)

    Hassager, Ole; Nielsen, Jens Kromann; Rasmussen, Henrik Koblitz

    2005-01-01

    The Filament Stretching Rheometry (FSR) method developed by Sridhar, McKinley and coworkers for polymer solutions has been extended to be used also for polymer melts. The design of a melt-FSR will be described and differences to conventional melt elongational rheometers will be pointed out. Results...

  7. Graphene-based filament material for thermal ionization

    Energy Technology Data Exchange (ETDEWEB)

    Hewitt, J. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Shick, C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Siegfried, M. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-09-19

    The use of graphene oxide materials for thermal ionization mass spectrometry analysis of plutonium and uranium has been investigated. Filament made from graphene oxide slurries have been 3-D printed. A method for attaching these filaments to commercial thermal ionization post assemblies has been devised. Resistive heating of the graphene based filaments under high vacuum showed stable operation in excess of 4 hours. Plutonium ion production has been observed in an initial set of filaments spiked with the Pu 128 Certified Reference Material.

  8. Solar filament material oscillations and drainage before eruption

    International Nuclear Information System (INIS)

    Bi, Yi; Jiang, Yunchun; Yang, Jiayan; Hong, Junchao; Li, Haidong; Yang, Dan; Yang, Bo

    2014-01-01

    Both large-amplitude longitudinal (LAL) oscillations and material drainage in a solar filament are associated with the flow of material along the filament axis, often followed by an eruption. However, the relationship between these two motions and a subsequent eruption event is poorly understood. We analyze a filament eruption using EUV imaging data captured by the Atmospheric Imaging Array on board the Solar Dynamics Observatory and the Hα images from the Global Oscillation Network Group. Hours before the eruption, the filament was activated, with one of its legs undergoing a slow rising motion. The asymmetric activation inclined the filament relative to the solar surface. After the active phase, LAL oscillations were observed in the inclined filament. The oscillation period increased slightly over time, which may suggest that the magnetic fields supporting the filament evolve to be flatter during the slow rising phase. After the oscillations, a significant amount of filament material was drained toward one filament endpoint, followed immediately by the violent eruption of the filament. The material drainage may further support the change in magnetic topology prior to the eruption. Moreover, we suggest that the filament material drainage could play a role in the transition from a slow to a fast rise of the erupting filament.

  9. Architecture and fine structure of gill filaments in the brown mussel, perna perna

    CSIR Research Space (South Africa)

    Gregory, MA

    1996-10-01

    Full Text Available attention was paid to filament architecture, enervation of filaments, number and type of cells populating filament epithelia and variations in epithelial cell morphotogy and cilia ultra structure. Filament shape was maintained by thickened chitin...

  10. Filamentary structures in dense plasma focus: Current filaments or vortex filaments?

    Energy Technology Data Exchange (ETDEWEB)

    Soto, Leopoldo, E-mail: lsoto@cchen.cl; Pavez, Cristian; Moreno, José [Comisión Chilena de Energía Nuclear, CCHEN, Casilla 188-D, Santiago (Chile); Center for Research and Applications in Plasma Physics and Pulsed Power, P4, Departamento de Ciencias Físicas, Facultad de Ciencias Exactas, Universidad Andrés Bello, República 220, Santiago (Chile); Castillo, Fermin [Universidad Nacional Autónoma de México, Cuernavaca, México (Mexico); Veloso, Felipe [Instituto de Física, Pontificia Universidad Católica de Chile, 7820436 Santiago (Chile); Auluck, S. K. H. [Bhabha Atomic Research Center, Mumbai 400 085 (India)

    2014-07-15

    Recent observations of an azimuthally distributed array of sub-millimeter size sources of fusion protons and correlation between extreme ultraviolet (XUV) images of filaments with neutron yield in PF-1000 plasma focus have re-kindled interest in their significance. These filaments have been described variously in literature as current filaments and vortex filaments, with very little experimental evidence in support of either nomenclature. This paper provides, for the first time, experimental observations of filaments on a table-top plasma focus device using three techniques: framing photography of visible self-luminosity from the plasma, schlieren photography, and interferometry. Quantitative evaluation of density profile of filaments from interferometry reveals that their radius closely agrees with the collision-less ion skin depth. This is a signature of relaxed state of a Hall fluid, which has significant mass flow with equipartition between kinetic and magnetic energy, supporting the “vortex filament” description. This interpretation is consistent with empirical evidence of an efficient energy concentration mechanism inferred from nuclear reaction yields.

  11. Genome erosion in a nitrogen-fixing vertically transmitted endosymbiotic multicellular cyanobacterium.

    Directory of Open Access Journals (Sweden)

    Liang Ran

    Full Text Available BACKGROUND: An ancient cyanobacterial incorporation into a eukaryotic organism led to the evolution of plastids (chloroplasts and subsequently to the origin of the plant kingdom. The underlying mechanism and the identities of the partners in this monophyletic event remain elusive. METHODOLOGY/PRINCIPAL FINDINGS: To shed light on this evolutionary process, we sequenced the genome of a cyanobacterium residing extracellularly in an endosymbiosis with a plant, the water-fern Azolla filiculoides Lam. This symbiosis was selected as it has characters which make it unique among extant cyanobacterial plant symbioses: the cyanobacterium lacks autonomous growth and is vertically transmitted between plant generations. Our results reveal features of evolutionary significance. The genome is in an eroding state, evidenced by a large proportion of pseudogenes (31.2% and a high frequency of transposable elements (approximately 600 scattered throughout the genome. Pseudogenization is found in genes such as the replication initiator dnaA and DNA repair genes, considered essential to free-living cyanobacteria. For some functional categories of genes pseudogenes are more prevalent than functional genes. Loss of function is apparent even within the 'core' gene categories of bacteria, such as genes involved in glycolysis and nutrient uptake. In contrast, serving as a critical source of nitrogen for the host, genes related to metabolic processes such as cell differentiation and nitrogen-fixation are well preserved. CONCLUSIONS/SIGNIFICANCE: This is the first finding of genome degradation in a plant symbiont and phenotypically complex cyanobacterium and one of only a few extracellular endosymbionts described showing signs of reductive genome evolution. Our findings suggest an ongoing selective streamlining of this cyanobacterial genome which has resulted in an organism devoted to nitrogen fixation and devoid of autonomous growth. The cyanobacterial symbiont of Azolla

  12. Macrolactone Nuiapolide, Isolated from a Hawaiian Marine Cyanobacterium, Exhibits Anti-Chemotactic Activity.

    Science.gov (United States)

    Mori, Shogo; Williams, Howard; Cagle, Davey; Karanovich, Kristopher; Horgen, F David; Smith, Roger; Watanabe, Coran M H

    2015-10-09

    A new bioactive macrolactone, nuiapolide (1) was identified from a marine cyanobacterium collected off the coast of Niihau, near Lehua Rock. The natural product exhibits anti-chemotactic activity at concentrations as low as 1.3 μM against Jurkat cells, cancerous T lymphocytes, and induces a G2/M phase cell cycle shift. Structural characterization of the natural product revealed the compound to be a 40-membered macrolactone with nine hydroxyl functional groups and a rare tert-butyl carbinol residue.

  13. Macrolactone Nuiapolide, Isolated from a Hawaiian Marine Cyanobacterium, Exhibits Anti-Chemotactic Activity

    OpenAIRE

    Mori, Shogo; Williams, Howard; Cagle, Davey; Karanovich, Kristopher; Horgen, F. David; Smith, Roger; Watanabe, Coran M. H.

    2015-01-01

    A new bioactive macrolactone, nuiapolide (1) was identified from a marine cyanobacterium collected off the coast of Niihau, near Lehua Rock. The natural product exhibits anti-chemotactic activity at concentrations as low as 1.3 μM against Jurkat cells, cancerous T lymphocytes, and induces a G2/M phase cell cycle shift. Structural characterization of the natural product revealed the compound to be a 40-membered macrolactone with nine hydroxyl functional groups and a rare tert-butyl carbinol re...

  14. Macrolactone Nuiapolide, Isolated from a Hawaiian Marine Cyanobacterium, Exhibits Anti-Chemotactic Activity

    Directory of Open Access Journals (Sweden)

    Shogo Mori

    2015-10-01

    Full Text Available A new bioactive macrolactone, nuiapolide (1 was identified from a marine cyanobacterium collected off the coast of Niihau, near Lehua Rock. The natural product exhibits anti-chemotactic activity at concentrations as low as 1.3 μM against Jurkat cells, cancerous T lymphocytes, and induces a G2/M phase cell cycle shift. Structural characterization of the natural product revealed the compound to be a 40-membered macrolactone with nine hydroxyl functional groups and a rare tert-butyl carbinol residue.

  15. The Effects of the Toxic Cyanobacterium Limnothrix (Strain AC0243 on Bufo marinus Larvae

    Directory of Open Access Journals (Sweden)

    Olivia Daniels

    2014-03-01

    Full Text Available Limnothrix (strain AC0243 is a cyanobacterium, which has only recently been identified as toxin producing. Under laboratory conditions, Bufo marinus larvae were exposed to 100,000 cells mL−1 of Limnothrix (strain AC0243 live cultures for seven days. Histological examinations were conducted post mortem and revealed damage to the notochord, eyes, brain, liver, kidney, pancreas, gastrointestinal tract, and heart. The histopathological results highlight the toxicological impact of this strain, particularly during developmental stages. Toxicological similarities to β-N-Methylamino-L-alanine are discussed.

  16. The Effects of the Toxic Cyanobacterium Limnothrix (Strain AC0243) on Bufo marinus Larvae

    Science.gov (United States)

    Daniels, Olivia; Fabbro, Larelle; Makiela, Sandrine

    2014-01-01

    Limnothrix (strain AC0243) is a cyanobacterium, which has only recently been identified as toxin producing. Under laboratory conditions, Bufo marinus larvae were exposed to 100,000 cells mL−1 of Limnothrix (strain AC0243) live cultures for seven days. Histological examinations were conducted post mortem and revealed damage to the notochord, eyes, brain, liver, kidney, pancreas, gastrointestinal tract, and heart. The histopathological results highlight the toxicological impact of this strain, particularly during developmental stages. Toxicological similarities to β-N-Methylamino-l-alanine are discussed. PMID:24662524

  17. Fabrication of PLA Filaments and its Printable Performance

    Science.gov (United States)

    Liu, Wenjie; Zhou, Jianping; Ma, Yuming; Wang, Jie; Xu, Jie

    2017-12-01

    Fused deposition modeling (FDM) is a typical 3D printing technology and preparation of qualified filaments is the basis. In order to prepare polylactic acid (PLA) filaments suitable for personalized FDM 3D printing, this article investigated the effect of factors such as extrusion temperature and screw speed on the diameter, surface roughness and ultimate tensile stress of the obtained PLA filaments. The optimal process parameters for fabrication of qualified filaments were determined. Further, the printable performance of the obtained PLA filaments for 3D objects was preliminarily explored.

  18. In situ ellipsometric study of surface immobilization of flagellar filaments

    Energy Technology Data Exchange (ETDEWEB)

    Kurunczi, S., E-mail: kurunczi@mfa.kfki.hu [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Nemeth, A.; Huelber, T. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Kozma, P. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Petrik, P. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Jankovics, H. [Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Sebestyen, A. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Vonderviszt, F. [Department of Photonics, Research Institute for Technical Physics and Materials Science, H-1121, Konkoly Thege Miklos ut 29-33, Budapest (Hungary); Department of Nanotechnology, Research Institute of Chemical and Process Engineering, Faculty of Information Technology, University of Pannonia, Egyetem u. 10, Veszprem, H-8200 (Hungary); Institute of Enzymology, Karolina ut 29-33, Budapest, H-1113 (Hungary); and others

    2010-10-15

    Protein filaments composed of thousands of subunits are promising candidates as sensing elements in biosensors. In this work in situ spectroscopic ellipsometry is applied to monitor the surface immobilization of flagellar filaments. This study is the first step towards the development of layers of filamentous receptors for sensor applications. Surface activation is performed using silanization and a subsequent glutaraldehyde crosslinking. Structure of the flagellar filament layers immobilized on activated and non-activated Si wafer substrates is determined using a two-layer effective medium model that accounted for the vertical density distribution of flagellar filaments with lengths of 300-1500 nm bound to the surface. The formation of the first interface layer can be explained by the multipoint covalent attachment of the filaments, while the second layer is mainly composed of tail pinned filaments floating upwards with the free parts. As confirmed by atomic force microscopy, covalent immobilization resulted in an increased surface density compared to absorption.

  19. Transition from linear- to nonlinear-focusing regime in filamentation

    Science.gov (United States)

    Lim, Khan; Durand, Magali; Baudelet, Matthieu; Richardson, Martin

    2014-01-01

    Laser filamentation in gases is often carried out in the laboratory with focusing optics to better stabilize the filament, whereas real-world applications of filaments frequently involve collimated or near-collimated beams. It is well documented that geometrical focusing can alter the properties of laser filaments and, consequently, a transition between a collimated and a strongly focused filament is expected. Nevertheless, this transition point has not been identified. Here, we propose an analytical method to determine the transition, and show that it corresponds to an actual shift in the balance of physical mechanisms governing filamentation. In high-NA conditions, filamentation is primarily governed by geometrical focusing and plasma effects, while the Kerr nonlinearity plays a more significant role as NA decreases. We find the transition between the two regimes to be relatively insensitive to the intrinsic laser parameters, and our analysis agrees well with a wide range of parameters found in published literature. PMID:25434678

  20. Morgellons disease: a filamentous borrelial dermatitis.

    Science.gov (United States)

    Middelveen, Marianne J; Stricker, Raphael B

    2016-01-01

    Morgellons disease (MD) is a dermopathy characterized by multicolored filaments that lie under, are embedded in, or project from skin. Although MD was initially considered to be a delusional disorder, recent studies have demonstrated that the dermopathy is associated with tickborne infection, that the filaments are composed of keratin and collagen, and that they result from proliferation of keratinocytes and fibroblasts in epithelial tissue. Culture, histopathological and molecular evidence of spirochetal infection associated with MD has been presented in several published studies using a variety of techniques. Spirochetes genetically identified as Borrelia burgdorferi sensu stricto predominate as the infective agent in most of the Morgellons skin specimens studied so far. Other species of Borrelia including Borrelia garinii , Borrelia miyamotoi , and Borrelia hermsii have also been detected in skin specimens taken from MD patients. The optimal treatment for MD remains to be determined.

  1. Helicity and Filament Channels? The Straight Twist!

    Science.gov (United States)

    Antiochos, Spiro K.

    2010-01-01

    One of the most important and most puzzling features of the coronal magnetic field is that it appears to have smooth magnetic structure with little evidence for non-potentiality except at special locations, photospheric polarity inversions lines where the non-potentiality is observed as a filament channel. This characteristic feature of the closed-field corona is highly unexpected given that photospheric motions continuously tangle its magnetic field. Although reconnection can eliminate some of the injected structure, it cannot destroy the helicity, which should build up to produce observable complexity. We propose that an inverse cascade process transports the injected helicity from the interior of closed flux regions to their boundaries, polarity inversion lines, creating filament channels. We describe how the helicity is injected and transported and calculate the relevant rates. We argue that one process, helicity transport, can explain both the observed lack and presence of structure in the coronal magnetic field.

  2. Laser filamentation mathematical methods and models

    CERN Document Server

    Lorin, Emmanuel; Moloney, Jerome

    2016-01-01

    This book is focused on the nonlinear theoretical and mathematical problems associated with ultrafast intense laser pulse propagation in gases and in particular, in air. With the aim of understanding the physics of filamentation in gases, solids, the atmosphere, and even biological tissue, specialists in nonlinear optics and filamentation from both physics and mathematics attempt to rigorously derive and analyze relevant non-perturbative models. Modern laser technology allows the generation of ultrafast (few cycle) laser pulses, with intensities exceeding the internal electric field in atoms and molecules (E=5x109 V/cm or intensity I = 3.5 x 1016 Watts/cm2 ). The interaction of such pulses with atoms and molecules leads to new, highly nonlinear nonperturbative regimes, where new physical phenomena, such as High Harmonic Generation (HHG), occur, and from which the shortest (attosecond - the natural time scale of the electron) pulses have been created. One of the major experimental discoveries in this nonlinear...

  3. Filament supply circuit for particle accelerator

    International Nuclear Information System (INIS)

    Thompson, C.C. Jr.; Malone, H.F.

    1975-01-01

    In a particle accelerator of the type employing ac primary power and a voltage multiplication apparatus to achieve the required high dc accelerating voltage, a filament supply circuit is powered by a portion of the ac primary power appearing at the last stage of the voltage multiplier. This ac power is applied across a voltage regulator circuit in the form of two zener diodes connected back to back. The threshold of the zeners is below the lowest peak-to-peak voltage of the ac voltage, so that the regulated voltage remains constant for all settings of the adjustable acceleration voltage. The regulated voltage is coupled through an adjustable resistor and an impedance-matching transformer to the accelerator filament. (auth)

  4. Merging and energy exchange between optical filaments

    Energy Technology Data Exchange (ETDEWEB)

    Georgieva, D. A., E-mail: dgeorgieva@tu-sofia.bg [Faculty of Applied Mathematics and Computer Science, Technical University of Sofia, 8 Kliment Ohridski Blvd., 1000 Sofia (Bulgaria); Kovachev, L. M. [Institute of Electronics, Bulgarian Academy of Sciences, 72 Tzarigradcko Chaussee Blvd., 1784 Sofia (Bulgaria)

    2015-10-28

    We investigate nonlinear interaction between collinear femtosecond laser pulses with power slightly above the critical for self-focusing P{sub cr} trough the processes of cross-phase modulation (CPM) and degenerate four-photon parametric mixing (FPPM). When there is no initial phase difference between the pulses we observe attraction between pulses due to CPM. The final result is merging between the pulses in a single filament with higher power. By method of moments it is found that the attraction depends on the distance between the pulses and has potential character. In the second case we study energy exchange between filaments. This process is described through FPPM scheme and requests initial phase difference between the waves.

  5. Expression of organophosphorus-degradation gene ( opd) in aggregating and non-aggregating filamentous nitrogen-fixing cyanobacteria

    Science.gov (United States)

    Li, Qiong; Tang, Qing; Xu, Xudong; Gao, Hong

    2010-11-01

    Genetic engineering in filamentous N2-fixing cyanobacteria usually involves Anabaena sp. PCC 7120 and several other non-aggregating species. Mass culture and harvest of such species are more energy consuming relative to aggregating species. To establish a gene transfer system for aggregating species, we tested many species of Anabaena and Nostoc, and identified Nostoc muscorum FACHB244 as a species that can be genetically manipulated using the conjugative gene transfer system. To promote biodegradation of organophosphorus pollutants in aquatic environments, we introduced a plasmid containing the organophosphorus-degradation gene ( opd) into Anabaena sp. PCC 7120 and Nostoc muscorum FACHB244 by conjugation. The opd gene was driven by a strong promoter, P psbA . From both species, we obtained transgenic strains having organophosphorus-degradation activities. At 25°C, the whole-cell activities of the transgenic Anabaena and Nostoc strains were 0.163±0.001 and 0.289±0.042 unit/μg Chl a, respectively. However, most colonies resulting from the gene transfer showed no activity. PCR and DNA sequencing revealed deletions or rearrangements in the plasmid in some of the colonies. Expression of the green fluorescent protein gene from the same promoter in Anabaena sp. PCC 7120 showed similar results. These results suggest that there is the potential to promote the degradation of organophosphorus pollutants with transgenic cyanobacteria and that selection of high-expression transgenic colonies is important for genetic engineering of Anabaena and Nostoc species. For the first time, we established a gene transfer and expression system in an aggregating filamentous N2-fixing cyanobacterium. The genetic manipulation system of Nostoc muscorum FACHB244 could be utilized in the elimination of pollutants and large-scale production of valuable proteins or metabolites.

  6. Filamented plasmas in laser ablation of solids

    Czech Academy of Sciences Publication Activity Database

    Davies, J.R.; Fajardo, M.; Kozlová, Michaela; Mocek, Tomáš; Polan, Jiří; Rus, Bedřich

    2009-01-01

    Roč. 51, č. 3 (2009), 035013/1-035013/12 ISSN 0741-3335 EU Projects: European Commission(XE) 12843 - TUIXS Grant - others:FCT(PT) POCI/FIS/59563/2004 Institutional research plan: CEZ:AV0Z10100523 Keywords : magneto-hydrodynamic modelling * perturbation * filaments * x-ray * plasma Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.409, year: 2009

  7. Laser induced white lighting of tungsten filament

    Science.gov (United States)

    Strek, W.; Tomala, R.; Lukaszewicz, M.

    2018-04-01

    The sustained bright white light emission of thin tungsten filament was induced under irradiation with focused beam of CW infrared laser diode. The broadband emission centered at 600 nm has demonstrated the threshold behavior on excitation power. Its intensity increased non-linearly with excitation power. The emission occurred only from the spot of focused beam of excitation laser diode. The white lighting was accompanied by efficient photocurrent flow and photoelectron emission which both increased non-linearly with laser irradiation power.

  8. Cold Milky Way HI Gas in Filaments

    Science.gov (United States)

    Kalberla, P. M. W.; Kerp, J.; Haud, U.; Winkel, B.; Ben Bekhti, N.; Flöer, L.; Lenz, D.

    2016-04-01

    We investigate data from the Galactic Effelsberg-Bonn H I Survey, supplemented with data from the third release of the Galactic All Sky Survey (GASS III) observed at Parkes. We explore the all-sky distribution of the local Galactic H I gas with | {v}{{LSR}}| \\lt 25 km s-1 on angular scales of 11‧-16‧. Unsharp masking is applied to extract small-scale features. We find cold filaments that are aligned with polarized dust emission and conclude that the cold neutral medium (CNM) is mostly organized in sheets that are, because of projection effects, observed as filaments. These filaments are associated with dust ridges, aligned with the magnetic field measured on the structures by Planck at 353 GHz. The CNM above latitudes | b| \\gt 20^\\circ is described by a log-normal distribution, with a median Doppler temperature TD = 223 K, derived from observed line widths that include turbulent contributions. The median neutral hydrogen (H I) column density is NH I ≃ 1019.1 cm-2. These CNM structures are embedded within a warm neutral medium with NH I ≃ 1020 cm-2. Assuming an average distance of 100 pc, we derive for the CNM sheets a thickness of ≲0.3 pc. Adopting a magnetic field strength of Btot = (6.0 ± 1.8) μG, proposed by Heiles & Troland, and assuming that the CNM filaments are confined by magnetic pressure, we estimate a thickness of 0.09 pc. Correspondingly, the median volume density is in the range 14 ≲ n ≲ 47 cm-3. The authors thank the Deutsche Forschungsgemeinschaft (DFG) for support under grant numbers KE757/11-1, KE757/7-3, KE757/7-2, KE757/7-1, and BE4823/1-1.

  9. Magnetization Modeling of Twisted Superconducting Filaments

    CERN Document Server

    Satiramatekul, T; Devred, Arnaud; Leroy, Daniel

    2007-01-01

    This paper presents a new Finite Element numerical method to analyze the coupling between twisted filaments in a superconducting multifilament composite wire. To avoid the large number of elements required by a 3D code, the proposed method makes use of the energy balance principle in a 2D code. The relationship between superconductor critical current density and local magnetic flux density is implemented in the program for the Bean and modified Kim models. The modeled wire is made up of six filaments twisted together and embedded in a lowresistivity matrix. Computations of magnetization cycle and of the electric field pattern have been performed for various twist pitch values in the case of a pure copper matrix. The results confirm that the maximum magnetization depends on the matrix conductivity, the superconductor critical current density, the applied field frequency, and the filament twist pitch. The simulations also lead to a practical criterion for wire design that can be used to assess whether or not th...

  10. The Magnetic Structure of Filament Barbs

    Science.gov (United States)

    Chae, Jongchul; Moon, Yong-Jae; Park, Young-Deuk

    2005-06-01

    There is a controversy about how features protruding laterally from filaments, called barbs, are magnetically structured. On 2004 August 3, we observed a filament that had well-developed barbs. The observations were performed using the 10 inch refractor of the Big Bear Solar Observatory. A fast camera was employed to capture images at five different wavelengths of the Hα line and successively record them on the basis of frame selection. The terminating points of the barbs were clearly discernable in the Hα images without any ambiguity. The comparison of the Hα images with the magnetograms taken by SOHO MDI revealed that the termination occurred above the minor polarity inversion line dividing the magnetic elements of the major polarity and those of the minor polarity. There is also evidence that the flux cancellation proceeded on the polarity inversion line. Our results together with similar other recent observations support the idea that filament barbs are cool matter suspended in local dips of magnetic field lines, formed by magnetic reconnection in the chromosphere.

  11. OSCILLATING FILAMENTS. I. OSCILLATION AND GEOMETRICAL FRAGMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    Gritschneder, Matthias; Heigl, Stefan; Burkert, Andreas, E-mail: gritschm@usm.uni-muenchen.de [University Observatory Munich, LMU Munich, Scheinerstrasse 1, D-81679 Munich (Germany)

    2017-01-10

    We study the stability of filaments in equilibrium between gravity and internal as well as external pressure using the grid-based AMR code RAMSES. A homogeneous, straight cylinder below a critical line mass is marginally stable. However, if the cylinder is bent, such as with a slight sinusoidal perturbation, an otherwise stable configuration starts to oscillate, is triggered into fragmentation, and collapses. This previously unstudied behavior allows a filament to fragment at any given scale, as long as it has slight bends. We call this process “geometrical fragmentation.” In our realization, the spacing between the cores matches the wavelength of the sinusoidal perturbation, whereas up to now, filaments were thought to be only fragmenting on the characteristic scale set by the mass-to-line ratio. Using first principles, we derive the oscillation period as well as the collapse timescale analytically. To enable a direct comparison with observations, we study the line-of-sight velocity for different inclinations. We show that the overall oscillation pattern can hide the infall signature of cores.

  12. A first approach to filament dynamics

    International Nuclear Information System (INIS)

    Silva, P E S; De Abreu, F Vistulo; Dias, R G; Simoes, R

    2010-01-01

    Modelling elastic filament dynamics is a topic of high interest due to the wide range of applications. However, it has reached a high level of complexity in the literature, making it unaccessible to a beginner. In this paper we explain the main steps involved in the computational modelling of the dynamics of an elastic filament. We first derive equations governing the dynamics of an elastic lament suitable for a computer simulation implementation. The derivation starts from the relation between forces and potential energy in conservative systems in order to derive the equation of motion of any bead in the filament. Only two-dimensional movements are considered, but extensions to three dimensions can follow similar lines. Suggestions for computer implementations are provided in Matlab as well as an example of application related to the generation of musical sounds. This example allows a critical analysis of the numerical results obtained using a cross-disciplinary perspective. Since derivations start from basic physics equations, use simple calculus and computational implementations are straightforward, this paper proposes a different approach to introduce simple molecular dynamics simulations or animations of real systems in undergraduate elasticity or computer modelling courses.

  13. Tracer filamentation at an unstable ocean front

    Science.gov (United States)

    Feng, Yen Chia; Mahadevan, Amala; Thiffeault, Jean-Luc; Yecko, Philip

    2017-11-01

    A front, where two bodies of ocean water with different physical properties meet, can become unstable and lead to a flow with high strain rate and vorticity. Phytoplankton and other oceanic tracers are stirred into filaments by such flow fields, as can often be seen in satellite imagery. The stretching and folding of a tracer by a two-dimensional flow field has been well studied. In the ocean, however, the vertical shear of horizontal velocity is typically two orders of magnitude larger than the horizontal velocity gradient. Theoretical calculations show that vertical shear alters the way in which horizontal strain affects the tracer, resulting in thin, sloping structures in the tracer field. Using a non-hydrostatic ocean model of an unstable ocean front, we simulate tracer filamentation to identify the effect of vertical shear on the deformation of the tracer. In a complementary laboratory experiment, we generate a simple, vertically sheared strain flow and use dye and particle image velocimetry to quantify the filamentary structures in terms of the strain and shear. We identify how vertical shear alters the tracer filaments and infer how the evolution of tracers in the ocean will differ from the idealized two-dimensional paradigm. Support of NSF DMS-1418956 is acknowledged.

  14. FILAMENT INTERACTION MODELED BY FLUX ROPE RECONNECTION

    International Nuclear Information System (INIS)

    Toeroek, T.; Chandra, R.; Pariat, E.; Demoulin, P.; Schmieder, B.; Aulanier, G.; Linton, M. G.; Mandrini, C. H.

    2011-01-01

    Hα observations of solar active region NOAA 10501 on 2003 November 20 revealed a very uncommon dynamic process: during the development of a nearby flare, two adjacent elongated filaments approached each other, merged at their middle sections, and separated again, thereby forming stable configurations with new footpoint connections. The observed dynamic pattern is indicative of 'slingshot' reconnection between two magnetic flux ropes. We test this scenario by means of a three-dimensional zero β magnetohydrodynamic simulation, using a modified version of the coronal flux rope model by Titov and Demoulin as the initial condition for the magnetic field. To this end, a configuration is constructed that contains two flux ropes which are oriented side-by-side and are embedded in an ambient potential field. The choice of the magnetic orientation of the flux ropes and of the topology of the potential field is guided by the observations. Quasi-static boundary flows are then imposed to bring the middle sections of the flux ropes into contact. After sufficient driving, the ropes reconnect and two new flux ropes are formed, which now connect the former adjacent flux rope footpoints of opposite polarity. The corresponding evolution of filament material is modeled by calculating the positions of field line dips at all times. The dips follow the morphological evolution of the flux ropes, in qualitative agreement with the observed filaments.

  15. On the fragmentation of filaments in a molecular cloud simulation

    Science.gov (United States)

    Chira, R.-A.; Kainulainen, J.; Ibáñez-Mejía, J. C.; Henning, Th.; Mac Low, M.-M.

    2018-03-01

    Context. The fragmentation of filaments in molecular clouds has attracted a lot of attention recently as there seems to be a close relation between the evolution of filaments and star formation. The study of the fragmentation process has been motivated by simple analytical models. However, only a few comprehensive studies have analysed the evolution of filaments using numerical simulations where the filaments form self-consistently as part of large-scale molecular cloud evolution. Aim. We address the early evolution of parsec-scale filaments that form within individual clouds. In particular, we focus on three questions: How do the line masses of filaments evolve? How and when do the filaments fragment? How does the fragmentation relate to the line masses of the filaments? Methods: We examine three simulated molecular clouds formed in kiloparsec-scale numerical simulations performed with the FLASH adaptive mesh refinement magnetohydrodynamic code. The simulations model a self-gravitating, magnetised, stratified, supernova-driven interstellar medium, including photoelectric heating and radiative cooling. We follow the evolution of the clouds for 6 Myr from the time self-gravity starts to act. We identify filaments using the DisPerSe algorithm, and compare the results to other filament-finding algorithms. We determine the properties of the identified filaments and compare them with the predictions of analytic filament stability models. Results: The average line masses of the identified filaments, as well as the fraction of mass in filamentary structures, increases fairly continuously after the onset of self-gravity. The filaments show fragmentation starting relatively early: the first fragments appear when the line masses lie well below the critical line mass of Ostriker's isolated hydrostatic equilibrium solution ( 16 M⊙ pc-1), commonly used as a fragmentation criterion. The average line masses of filaments identified in three-dimensional volume density cubes

  16. A Nostoc punctiforme sugar transporter necessary to establish a Cyanobacterium-plant symbiosis.

    Science.gov (United States)

    Ekman, Martin; Picossi, Silvia; Campbell, Elsie L; Meeks, John C; Flores, Enrique

    2013-04-01

    In cyanobacteria-plant symbioses, the symbiotic nitrogen-fixing cyanobacterium has low photosynthetic activity and is supplemented by sugars provided by the plant partner. Which sugars and cyanobacterial sugar uptake mechanism(s) are involved in the symbiosis, however, is unknown. Mutants of the symbiotically competent, facultatively heterotrophic cyanobacterium Nostoc punctiforme were constructed bearing a neomycin resistance gene cassette replacing genes in a putative sugar transport gene cluster. Results of transport activity assays using (14)C-labeled fructose and glucose and tests of heterotrophic growth with these sugars enabled the identification of an ATP-binding cassette-type transporter for fructose (Frt), a major facilitator permease for glucose (GlcP), and a porin needed for the optimal uptake of both fructose and glucose. Analysis of green fluorescent protein fluorescence in strains of N. punctiforme bearing frt::gfp fusions showed high expression in vegetative cells and akinetes, variable expression in hormogonia, and no expression in heterocysts. The symbiotic efficiency of N. punctiforme sugar transport mutants was investigated by testing their ability to infect a nonvascular plant partner, the hornwort Anthoceros punctatus. Strains that were specifically unable to transport glucose did not infect the plant. These results imply a role for GlcP in establishing symbiosis under the conditions used in this work.

  17. Sorption and desorption studies of chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass

    International Nuclear Information System (INIS)

    Gupta, V.K.; Rastogi, A.

    2008-01-01

    This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 o C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO 3 and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater

  18. Growth of Cyanobacterium aponinum influenced by increasing salt concentrations and temperature.

    Science.gov (United States)

    Winckelmann, Dominik; Bleeke, Franziska; Bergmann, Peter; Klöck, Gerd

    2015-06-01

    The increasing requirement of food neutral biofuels demands the detection of alternative sources. The use of non-arable land and waste water streams is widely discussed in this regard. A Cyanobacterium was isolated on the area of a possible algae production side near a water treatment plant in the arid desert region al-Wusta. It was identified as Cyanobacterium aponinum PB1 and is a possible lipid source. To determine its suitability of a production process using this organism, a set of laboratory experiments were performed. Its growth behavior was examined in regard to high temperatures and increasing NaCl concentrations. A productivity of 0.1 g L -1 per day was measured at an alga density below 0.75 g L -1 . C. aponinum PB1 showed no sign of altered growth behavior in media containing 70 g L -1 NaCl or less. Detection of a negative effect of NaCl on the growth using Pulse-Amplitude-Modulation chlorophyll fluorescence analysis was not more sensitive than optical density measurement.

  19. Unique thylakoid membrane architecture of a unicellular N2-fixing cyanobacterium revealed by electron tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liberton, Michelle; Austin II, Jotham R; Berg, R. Howard; Pakrasi, Himadri B

    2011-04-01

    Cyanobacteria, descendants of the endosymbiont that gave rise to modern-day chloroplasts, are vital contributors to global biological energy conversion processes. A thorough understanding of the physiology of cyanobacteria requires detailed knowledge of these organisms at the level of cellular architecture and organization. In these prokaryotes, the large membrane protein complexes of the photosynthetic and respiratory electron transport chains function in the intracellular thylakoid membranes. Like plants, the architecture of the thylakoid membranes in cyanobacteria has direct impact on cellular bioenergetics, protein transport, and molecular trafficking. However, whole-cell thylakoid organization in cyanobacteria is not well understood. Here we present, by using electron tomography, an in-depth analysis of the architecture of the thylakoid membranes in a unicellular cyanobacterium, Cyanothece sp. ATCC 51142. Based on the results of three-dimensional tomographic reconstructions of near-entire cells, we determined that the thylakoids in Cyanothece 51142 form a dense and complex network that extends throughout the entire cell. This thylakoid membrane network is formed from the branching and splitting of membranes and encloses a single lumenal space. The entire thylakoid network spirals as a peripheral ring of membranes around the cell, an organization that has not previously been described in a cyanobacterium. Within the thylakoid membrane network are areas of quasi-helical arrangement with similarities to the thylakoid membrane system in chloroplasts. This cyanobacterial thylakoid arrangement is an efficient means of packing a large volume of membranes in the cell while optimizing intracellular transport and trafficking.

  20. Unique Thylakoid Membrane Architecture of a Unicellular N2-Fixing Cyanobacterium Revealed by Electron Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liberton, Michelle L.; Austin, Jotham R.; Berg, R. H.; Pakrasi, Himadri B.

    2011-04-01

    Cyanobacteria, descendants of the endosymbiont that gave rise to modern-day chloroplasts, are vital contributors to global biological energy conversion processes. A thorough understanding of the physiology of cyanobacteria requires detailed knowledge of these organisms at the level of cellular architecture and organization. In these prokaryotes, the large membrane protein complexes of the photosynthetic and respiratory electron transport chains function in the intracellular thylakoid membranes. Like plants, the architecture of the thylakoid membranes in cyanobacteria has direct impact on cellular bioenergetics, protein transport, and molecular trafficking. However, whole-cell thylakoid organization in cyanobacteria is not well understood. Here we present, by using electron tomography, an in-depth analysis of the architecture of the thylakoid membranes in a unicellular cyanobacterium, Cyanothece sp. ATCC 51142. Based on the results of three-dimensional tomographic reconstructions of near-entire cells, we determined that the thylakoids in Cyanothece 51142 form a dense and complex network that extends throughout the entire cell. This thylakoid membrane network is formed from the branching and splitting of membranes and encloses a single lumenal space. The entire thylakoid network spirals as a peripheral ring of membranes around the cell, an organization that has not previously been described in a cyanobacterium. Within the thylakoid membrane network are areas of quasi-helical arrangement with similarities to the thylakoid membrane system in chloroplasts. This cyanobacterial thylakoid arrangement is an efficient means of packing a large volume of membranes in the cell while optimizing intracellular transport and trafficking.

  1. Combined Effects of CO2 and Light on the N-2-Fixing Cyanobacterium Trichodesmium IMS101: A Mechanistic View

    Czech Academy of Sciences Publication Activity Database

    Levitan, O.; Kranz, S. A.; Spungin, D.; Prášil, Ondřej; Rost, B.; Berman-Frank, I.

    2010-01-01

    Roč. 154, č. 1 (2010), s. 346-356 ISSN 0032-0889 R&D Projects: GA ČR GA206/08/1683 Institutional research plan: CEZ:AV0Z50200510 Keywords : cyanobacterium Trichodesmium * ocean * photosystem I Subject RIV: EE - Microbiology, Virology Impact factor: 6.451, year: 2010

  2. Combined effect of CO2 and light on the N2-fixing cyanobacterium Trichodesmium IMS101: Physiological responses 1[OA

    Czech Academy of Sciences Publication Activity Database

    Kranz, S. A.; Levitan, O.; Richter, K.-U.; Prášil, Ondřej; Berman-Frank, I.; Rost, B.

    2010-01-01

    Roč. 154, č. 1 (2010), s. 334-345 ISSN 0032-0889 R&D Projects: GA ČR GA206/08/1683 Institutional research plan: CEZ:AV0Z50200510 Keywords : Trichodesmium IMS101 * cyanobacterium * CO2 Subject RIV: EE - Microbiology, Virology Impact factor: 6.451, year: 2010

  3. Mono-, di- and trimeric PS I reaction center complexes isolated from the thermophilic cyanobacterium Synechococcus sp. Size, shape and activity

    NARCIS (Netherlands)

    Rögner, M.; Mühlenhoff, U.; Boekema, E.J.; Witt, H.T.

    1990-01-01

    Photosystem I preparations from the cyanobacterium Synechococcus sp. were treated with high concentrations of Tris and octyl glucoside at alkaline pH and elevated temperature. A sucrose density gradient yielded three pigment-protein complexes; these were further purified on a HPLC anion-exchange

  4. Two-Step Separation of Nostotrebin 6 from Cultivated Soil Cyanobacterium (Nostoc sp.) by High Performance Countercurrent Chromatography

    Czech Academy of Sciences Publication Activity Database

    Cheel, José; Kučerová, P.; Garrard, I.; Ignatova, S.; Hrouzek, Pavel; Kopecký, Jiří

    2014-01-01

    Roč. 19, č. 4 (2014), s. 8773-8787 ISSN 1420-3049 R&D Projects: GA MŠk ED2.1.00/03.0110; GA MŠk EE2.3.30.0059 Institutional support: RVO:61388971 Keywords : nostotrebin 6 * cyanobacterium * Nostoc * HPLC separation Subject RIV: EE - Microbiology, Virology Impact factor: 2.416, year: 2014

  5. Backbone dynamics of reduced plastocyanin from the cyanobacterium Anabaena variabilis: Regions involved in electron transfer have enhanced mobility

    DEFF Research Database (Denmark)

    Ma, L.X.; Hass, M.A.S.; Vierick, N.

    2003-01-01

    The dynamics of the backbone of the electron-transfer protein plastocyanin from the cyanobacterium Anabaena variabilis were determined from the N-15 and C-13(alpha) R-1 and R-2) relaxation rates and steady-state [H-1]-N-15 and [H-1]-C-13 nuclear Overhauser effects (NOEs) using the model...

  6. Pulsed nitrogen supply induces dynamic changes in the amino acid composition and microcystin production of the harmful cyanobacterium Planktothrix agardhii

    NARCIS (Netherlands)

    van de Waal, D.B.; Ferreruela, G.; Tonk, L.; van Donk, E.; Huisman, J.; Visser, P.M.; Matthijs, H.C.P.

    2010-01-01

    Planktothrix agardhii is a widespread harmful cyanobacterium of eutrophic waters, and can produce the hepatotoxins [Asp3]microcystin-LR and [Asp3]microcystin-RR. These two microcystin variants differ in their first variable amino acid position, which is occupied by either leucine (L) or arginine

  7. Pulsed nitrogen supply induces dynamic changes in the amino acid compositionand microcystin production of the harmful cyanobacterium Planktothrix agardhii

    NARCIS (Netherlands)

    Van de Waal, D.B.; Ferreruela, G.; Tonk, L.; Van Donk, E.; Huisman, J.; Visser, P.M.; Matthijs, H.C.P.

    2010-01-01

    Planktothrix agardhii is a widespread harmful cyanobacterium of eutrophic waters, and can produce the hepatotoxins [Asp3]microcystin-LR and [Asp3]microcystin-RR. These two microcystin variants differ in their first variable amino acid position, which is occupied by either leucine (L) or arginine

  8. Isolation and characterization of oxygen-evolving photosystem II particles and photosystem II core complex from the filamentous cyanobacterium Spirulina platensis

    Czech Academy of Sciences Publication Activity Database

    Šetlíková, Eva; Sofrová, D.; Kovář, V.; Budáč, Petr

    2013-01-01

    Roč. 51, č. 4 (2013), s. 517-530 ISSN 0300-3604 R&D Projects: GA ČR GA206/08/1683; GA MŠk(CZ) ED2.1.00/03.0110 Institutional support: RVO:61388971 Keywords : antibodies * fluorescence spectra * IMAC chromatography Subject RIV: EE - Microbiology, Virology Impact factor: 1.007, year: 2013

  9. Chirality of Intermediate Filaments and Magnetic Helicity of Active Regions

    Science.gov (United States)

    Lim, Eun-Kyung; Chae, J.

    2009-05-01

    Filaments that form either between or around active regions (ARs) are called intermediate filaments. Even though there have been many theoretical studies, the origin of the chirality of filaments is still unknown. We investigated how intermediate filaments are related to their associated ARs, especially from the point of view of magnetic helicity and the orientation of polarity inversion lines (PILs). The chirality of filaments has been determined based on the orientations of barbs observed in the full-disk Hα images taken at Big Bear Solar Observatory during the rising phase of solar cycle 23. The sign of magnetic helicity of ARs has been determined using S/inverse-S shaped sigmoids from Yohkoh SXT images. As a result, we have found a good correlation between the chirality of filaments and the magnetic helicity sign of ARs. Among 45 filaments, 42 filaments have shown the same sign as helicity sign of nearby ARs. It has been also confirmed that the role of both the orientation and the relative direction of PILs to ARs in determining the chirality of filaments is not significant, against a theoretical prediction. These results suggest that the chirality of intermediate filaments may originate from magnetic helicity of their associated ARs.

  10. Measuring Filament Orientation: A New Quantitative, Local Approach

    Energy Technology Data Exchange (ETDEWEB)

    Green, C.-E.; Cunningham, M. R.; Jones, P. A. [School of Physics, University of New South Wales, Sydney, NSW, 2052 (Australia); Dawson, J. R. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Novak, G. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208 (United States); Fissel, L. M. [National Radio Astronomy Observatory (NRAO), 520 Edgemont Road, Charlottesville, VA, 22903 (United States)

    2017-09-01

    The relative orientation between filamentary structures in molecular clouds and the ambient magnetic field provides insight into filament formation and stability. To calculate the relative orientation, a measurement of filament orientation is first required. We propose a new method to calculate the orientation of the one-pixel-wide filament skeleton that is output by filament identification algorithms such as filfinder. We derive the local filament orientation from the direction of the intensity gradient in the skeleton image using the Sobel filter and a few simple post-processing steps. We call this the “Sobel-gradient method.” The resulting filament orientation map can be compared quantitatively on a local scale with the magnetic field orientation map to then find the relative orientation of the filament with respect to the magnetic field at each point along the filament. It can also be used for constructing radial profiles for filament width fitting. The proposed method facilitates automation in analyses of filament skeletons, which is imperative in this era of “big data.”.

  11. Plasma Brightenings in a Failed Solar Filament Eruption

    Energy Technology Data Exchange (ETDEWEB)

    Li, Y.; Ding, M. D., E-mail: yingli@nju.edu.cn [School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China)

    2017-03-20

    Failed filament eruptions are solar eruptions that are not associated with coronal mass ejections. In a failed filament eruption, the filament materials usually show some ascending and falling motions as well as generating bright EUV emissions. Here we report a failed filament eruption (SOL2016-07-22) that occurred in a quiet-Sun region observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory . In this event, the filament spreads out but gets confined by the surrounding magnetic field. When interacting with the ambient magnetic field, the filament material brightens up and flows along the magnetic field lines through the corona to the chromosphere. We find that some materials slide down along the lifting magnetic structure containing the filament and impact the chromosphere, and through kinetic energy dissipation, cause two ribbon-like brightenings in a wide temperature range. There is evidence suggesting that magnetic reconnection occurs between the filament magnetic structure and the surrounding magnetic fields where filament plasma is heated to coronal temperatures. In addition, thread-like brightenings show up on top of the erupting magnetic fields at low temperatures, which might be produced by an energy imbalance from a fast drop of radiative cooling due to plasma rarefaction. Thus, this single event of a failed filament eruption shows the existence of a variety of plasma brightenings that may be caused by completely different heating mechanisms.

  12. Measuring Filament Orientation: A New Quantitative, Local Approach

    Science.gov (United States)

    Green, C.-E.; Dawson, J. R.; Cunningham, M. R.; Jones, P. A.; Novak, G.; Fissel, L. M.

    2017-09-01

    The relative orientation between filamentary structures in molecular clouds and the ambient magnetic field provides insight into filament formation and stability. To calculate the relative orientation, a measurement of filament orientation is first required. We propose a new method to calculate the orientation of the one-pixel-wide filament skeleton that is output by filament identification algorithms such as filfinder. We derive the local filament orientation from the direction of the intensity gradient in the skeleton image using the Sobel filter and a few simple post-processing steps. We call this the “Sobel-gradient method.” The resulting filament orientation map can be compared quantitatively on a local scale with the magnetic field orientation map to then find the relative orientation of the filament with respect to the magnetic field at each point along the filament. It can also be used for constructing radial profiles for filament width fitting. The proposed method facilitates automation in analyses of filament skeletons, which is imperative in this era of “big data.”

  13. Measuring Filament Orientation: A New Quantitative, Local Approach

    International Nuclear Information System (INIS)

    Green, C.-E.; Cunningham, M. R.; Jones, P. A.; Dawson, J. R.; Novak, G.; Fissel, L. M.

    2017-01-01

    The relative orientation between filamentary structures in molecular clouds and the ambient magnetic field provides insight into filament formation and stability. To calculate the relative orientation, a measurement of filament orientation is first required. We propose a new method to calculate the orientation of the one-pixel-wide filament skeleton that is output by filament identification algorithms such as filfinder. We derive the local filament orientation from the direction of the intensity gradient in the skeleton image using the Sobel filter and a few simple post-processing steps. We call this the “Sobel-gradient method.” The resulting filament orientation map can be compared quantitatively on a local scale with the magnetic field orientation map to then find the relative orientation of the filament with respect to the magnetic field at each point along the filament. It can also be used for constructing radial profiles for filament width fitting. The proposed method facilitates automation in analyses of filament skeletons, which is imperative in this era of “big data.”

  14. The Cape Ghir filament system in August 2009 (NW Africa)

    Science.gov (United States)

    Sangrà, Pablo; Troupin, Charles; Barreiro-González, Beatriz; Desmond Barton, Eric; Orbi, Abdellatif; Arístegui, Javier

    2015-06-01

    In the framework of the Canaries-Iberian marine ecosystem Exchanges (CAIBEX) experiment, an interdisciplinary high-resolution survey was conducted in the NW African region of Cape Ghir (30°38'N) during August 2009. The anatomy of a major filament is investigated on scales down to the submesoscale using in situ and remotely sensed data. The filament may be viewed as a system composed of three intimately connected structures: a small, shallow, and cold filament embedded within a larger, deeper, and cool filament and an intrathermocline anticyclonic eddy (ITE). The cold filament, which stretches 110 km offshore, is a shallow feature 60 m deep and 25 km wide, identified by minimal surface temperatures and rich in chlorophyll a. This structure comprises two asymmetrical submesoscale (˜18 km) fronts with jets flowing in opposite directions. The cold filament is embedded near the equatorward boundary of a much broader region of approximately 120 km width and 150 m depth that forms the cool filament and stretches at least 200 km offshore. This cool region, partly resulting from the influence of cold filament, is limited by two asymmetrical mesoscale (˜50 km) frontal boundaries. At the ITE, located north of the cold filament, we observe evidence of downwelling as indicated by a relatively high concentration of particles extending from the surface to more than 200 m depth. We hypothesize that this ITE may act as a sink of carbon and thus the filament system may serve dual roles of offshore carbon export and carbon sink.

  15. CalA, a Cyanobacterial AbrB Protein, Interacts with the Upstream Region of hypC and Acts as a Repressor of Its Transcription in the Cyanobacterium Nostoc sp. Strain PCC 7120▿ †

    Science.gov (United States)

    Agervald, Åsa; Zhang, Xiaohui; Stensjö, Karin; Devine, Ellenor; Lindblad, Peter

    2010-01-01

    The filamentous, heterocystous, nitrogen-fixing cyanobacterium Nostoc sp. strain PCC 7120 may contain, depending on growth conditions, up to two hydrogenases directly involved in hydrogen metabolism. HypC is one out of at least seven auxiliary gene products required for synthesis of a functional hydrogenase, specifically involved in the maturation of the large subunit. In this study we present a protein, CalA (Alr0946 in the genome), belonging to the transcription regulator family AbrB, which in protein-DNA assays was found to interact with the upstream region of hypC. Transcriptional investigations showed that calA is cotranscribed with the downstream gene alr0947, which encodes a putative protease from the abortive infection superfamily, Abi. CalA was shown to interact specifically not only with the upstream region of hypC but also with its own upstream region, acting as a repressor on hypC. The bidirectional hydrogenase activity was significantly downregulated when CalA was overexpressed, demonstrating a correlation with the transcription factor, either direct or indirect. In silico studies showed that homologues to both CalA and Alr0947 are highly conserved proteins within cyanobacteria with very similar physical organizations of the corresponding structural genes. Possible functions of the cotranscribed downstream protein Alr0947 are presented. In addition, we present a three-dimensional (3D) model of the DNA binding domain of CalA and putative DNA binding mechanisms are discussed. PMID:20023111

  16. Unravelling the cross-talk between iron starvation and oxidative stress responses highlights the key role of PerR (alr0957) in peroxide signalling in the cyanobacterium Nostoc PCC 7120.

    Science.gov (United States)

    Yingping, Fan; Lemeille, Sylvain; Talla, Emmanuel; Janicki, Annick; Denis, Yann; Zhang, Cheng-Cai; Latifi, Amel

    2014-10-01

    The cyanobacterial phylum includes oxygenic photosynthetic prokaryotes of a wide variety of morphologies, metabolisms and ecologies. Their adaptation to their various ecological niches is mainly achieved by sophisticated regulatory mechanisms and depends on a fine cross-talk between them. We assessed the global transcriptomic response of the filamentous cyanobacterium Nostoc PCC 7120 to iron starvation and oxidative stress. More than 20% of the differentially expressed genes in response to iron stress were also responsive to oxidative stress. These transcripts include antioxidant proteins-encoding genes that confirms that iron depletion leads to reactive oxygen accumulation. The activity of the Fe-superoxide dismutase was not significantly decreased under iron starvation, indicating that the oxidative stress generated under iron deficiency is not a consequence of (SOD) deficiency. The transcriptional data indicate that the adaptation of Nostoc to iron-depleted conditions displays important differences with what has been shown in unicellular cyanobacteria. While the FurA protein that regulates the response to iron deprivation has been well characterized in Nostoc, the regulators in charge of the oxidative stress response are unknown. Our study indicates that the alr0957 (perR) gene encodes the master regulator of the peroxide stress. PerR is a peroxide-sensor repressor that senses peroxide by metal-catalysed oxidation.

  17. The two Dps proteins, NpDps2 and NpDps5, are involved in light-induced oxidative stress tolerance in the N2-fixing cyanobacterium Nostoc punctiforme.

    Science.gov (United States)

    Moparthi, Vamsi K; Li, Xin; Vavitsas, Konstantinos; Dzhygyr, Ievgen; Sandh, Gustaf; Magnuson, Ann; Stensjö, Karin

    2016-11-01

    Cyanobacteria are photosynthetic prokaryotes that are considered biotechnologically prominent organisms for production of high-value compounds. Cyanobacteria are subject to high-light intensities, which is a challenge that needs to be addressed in design of efficient bio-engineered photosynthetic organisms. Dps proteins are members of the ferritin superfamily and are omnipresent in prokaryotes. They play a major role in oxidative stress protection and iron homeostasis. The filamentous, heterocyst-forming Nostoc punctiforme, has five Dps proteins. In this study we elucidated the role of these Dps proteins in acclimation to high light intensity, the gene loci organization and the transcriptional regulation of all five dps genes in N. punctiforme was revealed, and dps-deletion mutant strains were used in physiological characterization. Two mutants defective in Dps2 and Dps5 activity displayed a reduced fitness under increased illumination, as well as a differential Photosystem (PS) stoichiometry, with an elevated Photosystem II to Photosystem I ratio in the dps5 deletion strain. This work establishes a Dps-mediated link between light tolerance, H 2 O 2 detoxification, and iron homeostasis, and provides further evidence on the non-redundant role of multiple Dps proteins in this multicellular cyanobacterium. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. The THMIS-MTR observation of a active region filament

    Science.gov (United States)

    Zong, W. G.; Tang, Y. H.; Fang, C.

    We present some THMIS-MTR observations of a active region filament on September 4, 2002. The full stokes parameters of the filament were obtained in Hα, CaII 8542 and FeI 6302. By use of the data with high spatial resolution(0.44" per pixel), we probed the fine structure of the filament and gave out the parameters at the barbs' endpoints, including intensity, velocity and longitudinal magnetic field. Comparing the quiescent filament which we have discussed before, we find that: 1)The velocities of the barbs' endpoints are much bigger in the active region filament, the values are more than one thousand meters per second. 2)The barbs' endpoints terminate at the low logitudinal magnetic field in the active region filament, too.

  19. A filament supported by different magnetic field configurations

    Science.gov (United States)

    Guo, Y.; Schmieder, B.; Démoulin, P.; Wiegelmann, T.; Aulanier, G.; Török, T.; Bommier, V.

    2011-08-01

    A nonlinear force-free magnetic field extrapolation of vector magnetogram data obtained by THEMIS/MTR on 2005 May 27 suggests the simultaneous existence of different magnetic configurations within one active region filament: one part of the filament is supported by field line dips within a flux rope, while the other part is located in dips within an arcade structure. Although the axial field chirality (dextral) and the magnetic helicity (negative) are the same along the whole filament, the chiralities of the filament barbs at different sections are opposite, i.e., right-bearing in the flux rope part and left-bearing in the arcade part. This argues against past suggestions that different barb chiralities imply different signs of helicity of the underlying magnetic field. This new finding about the chirality of filaments will be useful to associate eruptive filaments and magnetic cloud using the helicity parameter in the Space Weather Science.

  20. Dynamics and mechanics of motor-filament systems

    Science.gov (United States)

    Kruse, K.; Jülicher, F.

    2006-08-01

    Motivated by the cytoskeleton of eukaryotic cells, we develop a general framework for describing the large-scale dynamics of an active filament network. In the cytoskeleton, active cross-links are formed by motor proteins that are able to induce relative motion between filaments. Starting from pair-wise interactions of filaments via such active processes, our framework is based on momentum conservation and an analysis of the momentum flux. This allows us to calculate the stresses in the filament network generated by the action of motor proteins. We derive effective theories for the filament dynamics which can be related to continuum theories of active polar gels. As an example, we discuss the stability of homogenous isotropic filament distributions in two spatial dimensions.

  1. Reduced filamentation in high power semiconductor lasers

    DEFF Research Database (Denmark)

    Skovgaard, Peter M. W.; McInerney, John; O'Brien, Peter

    1999-01-01

    High brightness semiconductor lasers have applications in fields ranging from material processing to medicine. The main difficulty associated with high brightness is that high optical power densities cause damage to the laser facet and thus require large apertures. This, in turn, results in spatio......-temporal instabilities such as filamentation which degrades spatial coherence and brightness. We first evaluate performance of existing designs with a “top-hat” shaped transverse current density profile. The unstable nature of highly excited semiconductor material results in a run-away process where small modulations...

  2. Dynamic Regulation of Sarcomeric Actin Filaments in Striated Muscle

    OpenAIRE

    Ono, Shoichiro

    2010-01-01

    In striated muscle, the actin cytoskeleton is differentiated into myofibrils. Actin and myosin filaments are organized in sarcomeres and specialized for producing contractile forces. Regular arrangement of actin filaments with uniform length and polarity is critical for the contractile function. However, the mechanisms of assembly and maintenance of sarcomeric actin filaments in striated muscle are not completely understood. Live imaging of actin in striated muscle has revealed that actin sub...

  3. Observations of the Growth of an Active Region Filament

    Science.gov (United States)

    Yang, Bo

    2017-04-01

    We present observations of the growth of an active region filament caused by magnetic interactions among the filament and its adjacent superpenumbral filament (SF) and dark thread-like structures (T). Multistep reconnections are identified during the whole growing process. Magnetic flux convergence and cancellation occurring at the positive footpoint region of the filament is the first step reconnection, which resulted in the filament bifurcating into two sets of intertwined threads. One set anchored in situ, while the other set moved toward and interacted with the SF and part of T. This indicates the second step reconnection, which gave rise to the disappearance of the SF and the formation of a long thread-like structure that connects the far ends of the filament and T. The long thread-like structure further interacted with the T and then separated into two parts, representing the third step reconnection. Finally, another similar long thread-like structure, which intertwined with the fixed filament threads, appeared. Hαobservations show that this twisted structure is a longer sinistral filament. Based on the observed photospheric vector magnetograms, we performed a non-linear force-free field extrapolation to reconstruct the magnetic fields above the photosphere and found that the coronal magnetic field lines associated with the filament consists of two twisted flux ropes winding around each other. These results suggest that magnetic interactions among filaments and their adjacent SFs and T could lead to the growth of the filaments, and the filament is probably supported in a flux rope.

  4. Modeling Vertical Plasma Flows in Solar Filament Barbs

    Science.gov (United States)

    Litvinenko, Y.

    2003-12-01

    Speeds of observed flows in quiescent solar filaments are typically much less than the local Alfvén speed. This is why the flows in filament barbs can be modeled by perturbing a local magnetostatic solution describing the balance between the Lorentz force, gravity, and gas pressure in a barb. Similarly, large-scale filament flows can be treated as adiabatically slow deformations of a force-free magnetic equilibrium that describes the global structure of a filament. This approach reconciles current theoretical models with the puzzling observational result that some of the flows appear to be neither aligned with the magnetic field nor controlled by gravity.

  5. Filament shape versus coronal potential magnetic field structure

    Science.gov (United States)

    Filippov, B.

    2016-01-01

    Solar filament shape in projection on disc depends on the structure of the coronal magnetic field. We calculate the position of polarity inversion lines (PILs) of coronal potential magnetic field at different heights above the photosphere, which compose the magnetic neutral surface, and compare with them the distribution of the filament material in Hα chromospheric images. We found that the most of the filament material is enclosed between two PILs, one at a lower height close to the chromosphere and one at a higher level, which can be considered as a height of the filament spine. Observations of the same filament on the limb by the Solar Terrestrial Relations Observatory spacecraft confirm that the height of the spine is really very close to the value obtained from the PIL and filament border matching. Such matching can be used for filament height estimations in on-disc observations. Filament barbs are housed within protruding sections of the low-level PIL. On the base of simple model, we show that the similarity of the neutral surfaces in potential and non-potential fields with the same sub-photospheric sources is the reason for the found tendency for the filament material to gather near the potential-field neutral surface.

  6. Statistical Study of the Magnetic Field Orientation in Solar Filaments

    Science.gov (United States)

    Hanaoka, Yoichiro; Sakurai, Takashi

    2017-12-01

    We have carried out a statistical study of the average orientation of the magnetic field in solar filaments with respect to their axes for more than 400 samples, based on data taken with daily full-Sun, full-Stokes spectropolarimetric observations using the He I 1083.0 nm line. The major part of the samples are the filaments in the quiet areas, but those in the active areas are included as well. The average orientation of the magnetic field in filaments shows a systematic property depending on the hemisphere; the direction of the magnetic field in filaments in the northern (southern) hemisphere mostly deviates clockwise (counterclockwise) from their axes, which run along the magnetic polarity inversion line. The deviation angles of the magnetic field from the axes are concentrated between 10° and 30°. This hemispheric pattern is consistent with that revealed for chirality of filament barbs, filament channels, and for other solar features found to possess chirality. For some filaments, it was confirmed that their magnetic field direction is locally parallel to their structure seen in Hα images. Our results for the first time confirmed this hemispheric pattern with the direct observation of the magnetic field in filaments. Interestingly, the filaments which show the opposite magnetic field deviation to the hemispheric pattern, are in many cases found above the polarity inversion line whose ambient photospheric magnetic field has the polarity alignment being opposite to that of active regions following the Hale–Nicholson law.

  7. Probabilities of filaments in a Poissonian distribution of points -I

    International Nuclear Information System (INIS)

    Betancort-Rijo, J.

    1989-01-01

    Statistical techniques are devised to assess the likelihood of a Poisson sample of points in two and three dimensions, containing specific filamentary structures. For that purpose, the expression of Otto et al (1986. Astrophys. J., 304) for the probability density of clumps in a Poissonian distribution of points is generalized for any value of the density contrast. A way of counting filaments differing from that of Otto et al. is proposed, because at low density contrast the filaments counted by Otto et al. are distributed in a clumpy fashion, each clump of filaments corresponding to a distinct observed filament. (author)

  8. MATERIAL SUPPLY AND MAGNETIC CONFIGURATION OF AN ACTIVE REGION FILAMENT

    Energy Technology Data Exchange (ETDEWEB)

    Zou, P.; Fang, C.; Chen, P. F.; Yang, K.; Hao, Q. [School of Astronomy and Space Science, Nanjing University, Nanjing 210023 (China); Cao, Wenda, E-mail: fangc@nju.edu.cn [Big Bear Solar Observatory, New Jersey Institute of Technology, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

    2016-11-10

    It is important to study the fine structures of solar filaments with high-resolution observations, since it can help us understand the magnetic and thermal structures of the filaments and their dynamics. In this paper, we study a newly formed filament located inside the active region NOAA 11762, which was observed by the 1.6 m New Solar Telescope at Big Bear Solar Observatory from 16:40:19 UT to 17:07:58 UT on 2013 June 5. As revealed by the H α filtergrams, cool material is seen to be injected into the filament spine with a speed of 5–10 km s{sup -1}. At the source of the injection, brightenings are identified in the chromosphere, which are accompanied by magnetic cancellation in the photosphere, implying the importance of magnetic reconnection in replenishing the filament with plasmas from the lower atmosphere. Counter-streamings are detected near one endpoint of the filament, with the plane-of-the-sky speed being 7–9 km s{sup -1} in the H α red-wing filtergrams and 9–25 km s{sup -1} in the blue-wing filtergrams. The observations are indicative that this active region filament is supported by a sheared arcade without magnetic dips, and the counter-streamings are due to unidirectional flows with alternative directions, rather than due to the longitudinal oscillations of filament threads as in many other filaments.

  9. Numerical simulation of laser filamentation in underdense plasma

    International Nuclear Information System (INIS)

    Yu Lichun; Chen Zhihua; Tu Qinfen

    2000-01-01

    Developing process of filamentation and effect of characteristic parameters in underdense plasma have been studied using numerical simulation method. Production and development of two-dimensional cylinder filamentation instability were presented clearly. The results indicate incidence laser intensity and plasma background density are important factors affecting convergent intensity. At the same time, it was showed that different laser wavelength or different electron background density could affect filamentation process. The results are consistent with theory and experiments of alien reports. It can provide reference for restraining filamentation

  10. Hollow cylindrical plasma filament waveguide with discontinuous finite thickness cladding

    International Nuclear Information System (INIS)

    Alshershby, Mostafa; Hao Zuoqiang; Lin Jingquan

    2013-01-01

    We have explored here a hollow cylindrical laser plasma multifilament waveguide with discontinuous finite thickness cladding, in which the separation between individual filaments is in the range of several millimeters and the waveguide cladding thickness is in the order of the microwave penetration depth. Such parameters give a closer representation of a realistic laser filament waveguide sustained by a long stable propagation of femtosecond (fs) laser pulses. We report how the waveguide losses depend on structural parameters like normalized plasma filament spacing, filament to filament distance or pitch, normal spatial frequency, and radius of the plasma filament. We found that for typical plasma parameters, the proposed waveguide can support guided modes of microwaves in extremely high frequency even with a cladding consisting of only one ring of plasma filaments. The loss of the microwave radiation is mainly caused by tunneling through the discontinuous finite cladding, i.e., confinement loss, and is weakly dependent on the plasma absorption. In addition, the analysis indicates that the propagation loss is fairly large compared with the loss of a plasma waveguide with a continuous infinite thickness cladding, while they are comparable when using a cladding contains more than one ring. Compared to free space propagation, this waveguide still presents a superior microwave transmission to some distance in the order of the filamentation length; thus, the laser plasma filaments waveguide may be a potential channel for transporting pulsed-modulated microwaves if ensuring a long and stable propagation of fs laser pulses.

  11. Intermediate filament mechanics in vitro and in the cell: From coiled coils to filaments, fibers and networks

    OpenAIRE

    Köster, Sarah; Weitz, David; Goldman, Robert D.; Aebi, Ueli; Herrmann, Harald

    2015-01-01

    Intermediate filament proteins form filaments, fibers and networks both in the cytoplasm and the nucleus of metazoan cells. Their general structural building plan accommodates highly varying amino acid sequences to yield extended dimeric α-helical coiled coils of highly conserved design. These “rod” particles are the basic building blocks of intrinsically flexible, filamentous structures that are able to resist high mechanical stresses, i.e. bending and stretching to a considerable degree, bo...

  12. Morgellons disease: a filamentous borrelial dermatitis

    Directory of Open Access Journals (Sweden)

    Middelveen MJ

    2016-10-01

    Full Text Available Marianne J Middelveen, Raphael B Stricker International Lyme and Associated Diseases Society, Bethesda, MD, USA Abstract: Morgellons disease (MD is a dermopathy characterized by multicolored filaments that lie under, are embedded in, or project from skin. Although MD was initially considered to be a delusional disorder, recent studies have demonstrated that the dermopathy is associated with tickborne infection, that the filaments are composed of keratin and collagen, and that they result from proliferation of keratinocytes and fibroblasts in epithelial tissue. Culture, histopathological and molecular evidence of spirochetal infection associated with MD has been presented in several published studies using a variety of techniques. Spirochetes genetically identified as Borrelia burgdorferi sensu stricto predominate as the infective agent in most of the Morgellons skin specimens studied so far. Other species of Borrelia including Borrelia garinii, Borrelia miyamotoi, and Borrelia hermsii have also been detected in skin specimens taken from MD patients. The optimal treatment for MD remains to be determined. Keywords: Morgellons disease, dermatitis, Lyme disease, Borrelia burgdorferi, spirochetes

  13. Laser filament-induced aerosol formation

    Directory of Open Access Journals (Sweden)

    H. Saathoff

    2013-05-01

    Full Text Available Using the aerosol and cloud simulation chamber AIDA, we investigated the laser filament induced particle formation in ambient air, humid synthetic air, humid nitrogen, argon–oxygen mixture, and pure argon in order to simulate the particle formation under realistic atmospheric conditions as well as to investigate the influence of typical gas-phase atmospheric constituents on the particle formation. Terawatt laser plasma filaments generated new particles in the size range 3 to 130 nm with particle production rates ranging from 1 × 107 to 5 × 109 cm−3 plasma s−1 for the given experimental conditions. In all cases the particle formation rates increased exponentially with the water content of the gas mixture. Furthermore, the presence of a few ppb of trace gases like SO2 and α-pinene clearly enhanced the particle yield by number, the latter also by mass. Our findings suggest that new particle formation is efficiently supported by oxidized species like acids generated by the photoionization of both major and minor components of the air, including N2, NH3, SO2 and organics.

  14. Mass motions in a quiescent filament

    International Nuclear Information System (INIS)

    Malherbe, J.M.; Mein, P.; Schmieder, B.

    1982-01-01

    Observations are presented of the sudden disappearance of a filament (N2O, E35) above an active region with the Multichannel Substractive Double Pass Spectrograph operating on the Meudon Solar Tower, France, from 10:45 UT to 13:30 UT on June 22, 1981. Measurements of the velocity fields and intensity fluctuations were obtained. It was found that the sudden disappearance did not take place simultaneously in all parts of the filament: thin threads with upward radial velocities reaching about 50 km/s were successively observed inside the prominence from the south to north regions. It is suggested that these motions corresponded to the rise of material along magnetic loops closely related to the prominence structure. An investigation of the dynamics inside such a magnetic loop shows a strongly accelerated high speed flow and a deformation of the flux tube, probably due to the centrifugal forces exerted by the flow on the magnetic lines. In addition, it is shown that the present theoretical models cannot account for the prominence structure as a cold H-alpha loop system and the acceleration process of material inside such loops

  15. Electromechanical vortex filaments during cardiac fibrillation

    Science.gov (United States)

    Christoph, J.; Chebbok, M.; Richter, C.; Schröder-Schetelig, J.; Bittihn, P.; Stein, S.; Uzelac, I.; Fenton, F. H.; Hasenfuß, G.; Gilmour, R. F., Jr.; Luther, S.

    2018-03-01

    The self-organized dynamics of vortex-like rotating waves, which are also known as scroll waves, are the basis of the formation of complex spatiotemporal patterns in many excitable chemical and biological systems. In the heart, filament-like phase singularities that are associated with three-dimensional scroll waves are considered to be the organizing centres of life-threatening cardiac arrhythmias. The mechanisms that underlie the onset, maintenance and control of electromechanical turbulence in the heart are inherently three-dimensional phenomena. However, it has not previously been possible to visualize the three-dimensional spatiotemporal dynamics of scroll waves inside cardiac tissues. Here we show that three-dimensional mechanical scroll waves and filament-like phase singularities can be observed deep inside the contracting heart wall using high-resolution four-dimensional ultrasound-based strain imaging. We found that mechanical phase singularities co-exist with electrical phase singularities during cardiac fibrillation. We investigated the dynamics of electrical and mechanical phase singularities by simultaneously measuring the membrane potential, intracellular calcium concentration and mechanical contractions of the heart. We show that cardiac fibrillation can be characterized using the three-dimensional spatiotemporal dynamics of mechanical phase singularities, which arise inside the fibrillating contracting ventricular wall. We demonstrate that electrical and mechanical phase singularities show complex interactions and we characterize their dynamics in terms of trajectories, topological charge and lifetime. We anticipate that our findings will provide novel perspectives for non-invasive diagnostic imaging and therapeutic applications.

  16. Molecular cloning of a recA-like gene from the cyanobacterium Anabaena variabilis

    International Nuclear Information System (INIS)

    Owttrim, G.W.; Coleman, J.R.

    1987-01-01

    A recA-like gene isolated from the cyanobacterium Anabaena variabilis was cloned and partially characterized. When introduced into Escherichia coli recA mutants, the 7.5-kilobase-pair plasmid-borne DNA insert restored resistance to methyl methanesulfonate and UV irradiation, as well as recombination proficiency when measured by Hfr-mediated conjugation. The cyanobacterial recA gene restored spontaneous but not mitomycin C-induced prophage production. Restriction analysis and subcloning yielded a 1.5-kilobase-pair Sau3A fragment which also restored methylmethane sulfonate resistance and coded for a 38- to 40-kilodalton polypeptide when expressed in an in vitro transcription-translation system

  17. Enhanced production of biomass, pigments and antioxidant capacity of a nutritionally important cyanobacterium Nostochopsis lobatus.

    Science.gov (United States)

    Pandey, Usha; Pandey, J

    2008-07-01

    A diazotrophic cyanobacterium Nostochopsis lobatus was evaluated for enhanced production of biomass, pigments and antioxidant capacity. N. lobatus showed potentially high antioxidant capacity (46.12 microM AEAC) with significant improvement under immobilized cell cultures (87.05 microM AEAC). When a mixture of P and Fe was supplemented, biomass, pigments, nutritive value and antioxidant capacity increased substantially at pH 7.8. When considered separately, P appeared to be a better supplement than Fe for the production of biomass, chlorophyll and carotenoids. However, for phycocyanin, phycoerythrin, nutritive value and antioxidant capacity, Fe appeared more effective than P. Our study indicates N. lobatus to be a promising bioresource for enhanced production of nutritionally rich biomass, pigments and antioxidants. The study also suggests that P and Fe are potentially effective supplements for scale-up production for commercial application.

  18. The complex effects of ocean acidification on the prominent N2-fixing cyanobacterium Trichodesmium.

    Science.gov (United States)

    Hong, Haizheng; Shen, Rong; Zhang, Futing; Wen, Zuozhu; Chang, Siwei; Lin, Wenfang; Kranz, Sven A; Luo, Ya-Wei; Kao, Shuh-Ji; Morel, François M M; Shi, Dalin

    2017-05-05

    Acidification of seawater caused by anthropogenic carbon dioxide (CO 2 ) is anticipated to influence the growth of dinitrogen (N 2 )-fixing phytoplankton, which contribute a large fraction of primary production in the tropical and subtropical ocean. We found that growth and N 2 -fixation of the ubiquitous cyanobacterium Trichodesmium decreased under acidified conditions, notwithstanding a beneficial effect of high CO 2 Acidification resulted in low cytosolic pH and reduced N 2 -fixation rates despite elevated nitrogenase concentrations. Low cytosolic pH required increased proton pumping across the thylakoid membrane and elevated adenosine triphosphate production. These requirements were not satisfied under field or experimental iron-limiting conditions, which greatly amplified the negative effect of acidification. Copyright © 2017, American Association for the Advancement of Science.

  19. Microbial interactions with the cyanobacterium Microcystis aeruginosa and their dependence on temperature

    DEFF Research Database (Denmark)

    Dziallas, Claudia; Grossart, Hans-Peter

    2012-01-01

    and their associated community often masked this temperature effect. Both macro- and microenvironment of active cyanobacterial strains were characterized by high pH and oxygen values creating a unique habitat that potentially affects microbial diversity and function. For example, archaea including ‘anaerobic......Associated heterotrophic bacteria alter the microenvironment of cyanobacteria and potentially influence cyanobacterial development. Therefore, we studied interactions of the unicellular freshwater cyanobacterium Microcystis aeruginosa with heterotrophic bacteria. The associated bacterial community...... was greatly driven by temperature as seen by DNA Wngerprinting. However, the associated microbes also closely interacted with the cyanobacteria indicating changing ecological consequence of the associated bacterial community with temperature. Whereas concentration of dissolved organic carbon in cyanobacterial...

  20. Sacrolide A, a new antimicrobial and cytotoxic oxylipin macrolide from the edible cyanobacterium Aphanothece sacrum

    Directory of Open Access Journals (Sweden)

    Naoya Oku

    2014-08-01

    Full Text Available Macroscopic gelatinous colonies of freshwater cyanobacterium Aphanothece sacrum, a luxury ingredient for Japanese cuisine, were found to contain a new oxylipin-derived macrolide, sacrolide A (1, as an antimicrobial component. The configuration of two chiral centers in 1 was determined by a combination of chiral anisotropy analysis and conformational analysis of different ring-opened derivatives. Compound 1 inhibited the growth of some species of Gram-positive bacteria, yeast Saccharomyces cerevisiae and fungus Penicillium chrysogenum, and was also cytotoxic to 3Y1 rat fibroblasts. Concern about potential food intoxication caused by accidental massive ingestion of A. sacrum was dispelled by the absence of 1 in commercial products. A manual procedure for degrading 1 in raw colonies was also developed, enabling a convenient on-site detoxification at restaurants or for personal consumption.

  1. Space-environmental tolerances in a cyanobacterium, Nostoc sp. HK-01

    Science.gov (United States)

    Tomita-Yokotani, Kaori; Yokobori, Shin-ichi; Kimura, Shunta; Sato, Seigo; Katoh, Hiroshi; Ajioka, Reiko; Yamagishi, Akihiko; Inoue, Kotomi

    2016-07-01

    We have been investigating the tolerances to space-environments of a cyanobacterium, Nostoc sp. HK-01 (hereafter referred to as HK-01). Dry colonies of HK-01 had high tolerance to dry conditions, but more detailed information about tolerance to high-temperature, UV, gamma-ray and heavy particle beams were not deeply investigated. The obtained dry colonies of HK-01 after exposure to each of the conditions described above were investigated. In all of the tested colonies of HK-01 after exposure, all or some of the cells in the colonies were alive. One of the purposes of space agriculture is growing plants on Mars. In the early stages, of our research, cyanobacteria are introduced on Mars to promote the oxidation of the atmosphere and the formation of soil from Mars's regolith. HK-01 will contribute to each of these factors in the future.

  2. Cadmium-mediated resistance to metals and antibiotics in a cyanobacterium

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.P.; Pandey, A.K.

    1982-01-01

    Cadmium-resistant strains of the cyanobacterium Nostoc calcicola were isolated through the step-wise transfer of the organism to higher levels of the metal. One of the Cd-resistant strains (CDsup(r)-10) showed cross-resistance to antibiotics like neomycin (1 ..mu..g/ml), chloramphenicol (3 ..mu..g/ml) but not to streptomycin. The Cd-resistant strain also tolerated elevated levels of metals such as zinc 20 ppm) and mercury (1 ppm). The stability of the metal-resistance required the presence of Cd/sup 2 +/ ions in the growth medium. It is suggested that metal resistance may also be determined by gene(s) on the antibiotic resistance plasmids in cyanobacteria.

  3. Utilization of a terrestrial cyanobacterium, Nostoc sp. HK-01, for space habitation

    Science.gov (United States)

    Kimura, Shunta; Tomita-Yokotani, Kaori; Arai, Mayumi; Yamashita, Masamichi; Katoh, Hiroshi; Ajioka, Reiko; Inoue, Kotomi

    2016-07-01

    A terrestrial cyanobacterium, Nostoc sp. HK-01 (hereafter HK-01), has several useful abilities for space habitation; photosynthesis, nitrogen fixation, and space environmental tolerances to vacuum, UV, gamma-ray, heavy particle beam, low and high temperature. Space environmental tolerances are important for transportation to Mars. HK-01 can grow on Martian regolith simulant (MRS) in vitro. Furthermore, HK-01 is useful as food. HK-01 may be utilized as oxygen supply, soil formation and food material for bio-chemical circulation in closed bio-ecosystems, including space habitation such as Mars. HK-01 was adopted as a biological material for the "TANPOPO" mission (JAXA et al.,), because of their high environmental tolerances. The "TANPOPO" mission is performing the space exposure experiments on the Japan Experimental Module (JEM) of the International Space Station (ISS). The results of these experiments will show the ability of HK-01 to survive in space.

  4. Composition and occurrence of lipid droplets in the cyanobacterium Nostoc punctiforme.

    Science.gov (United States)

    Peramuna, Anantha; Summers, Michael L

    2014-12-01

    Inclusions of neutral lipids termed lipid droplets (LDs) located throughout the cell were identified in the cyanobacterium Nostoc punctiforme by staining with lipophylic fluorescent dyes. LDs increased in number upon entry into stationary phase and addition of exogenous fructose indicating a role for carbon storage, whereas high-light stress did not increase LD numbers. LD accumulation increased when nitrate was used as the nitrogen source during exponential growth as compared to added ammonia or nitrogen-fixing conditions. Analysis of isolated LDs revealed enrichment of triacylglycerol (TAG), α-tocopherol, and C17 alkanes. LD TAG from exponential phase growth contained mainly saturated C16 and C18 fatty acids, whereas stationary phase LD TAG had additional unsaturated fatty acids characteristic of whole cells. This is the first characterization of cyanobacterial LD composition and conditions leading to their production. Based upon their abnormally large size and atypical location, these structures represent a novel sub-organelle in cyanobacteria.

  5. Phycobiliprotein accumulation in cyanobacterium Nostoc linckia and modification of antioxidant activity

    Directory of Open Access Journals (Sweden)

    Ana VALUTA

    2015-01-01

    Full Text Available The article deals with iron(III coordination compounds with Schiff bases as ligands and their impact on phycobiliprotein accumulation by cyanobacterium Nostoc linckia. Stimulatory effect depends on the applied dose and in case of three compounds, the concentration 20 mg/L was determined as one with moderate intensity. Lower concentrations resulted in an increase of the phycobiliprotein synthesis. There was found a significant positive correlation between phycobiliprotein content and ABTS (2.2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid assay values displayed by aqueous extracts from Nostoc linckia biomass cultivated in nutrient medium with these coordination compounds. Hence, it is possible to modify the antioxidant activity of Nostoc biomass by applying low concentrations of chemical stimuli.

  6. Heterologous expression of an algal hydrogenase in a hetero-cystous cyanobacterium

    Energy Technology Data Exchange (ETDEWEB)

    Thorsten Heidorn; Peter Lindblad [Dept. of Physiological Botany, Uppsala University, V illavagen 6, SE-752 36 Uppsala, (Sweden)

    2006-07-01

    For the expression of an active algal [FeFe] hydrogenase in the hetero-cystous cyanobacterium Nostoc punctiforme A TCC 29133 the Chlamydomonas reinhardtii hydrogenase gene hydA1 and the accessory genes hydEF and hydG are to be introduced into the cyano-bacterial cells. The genes were amplified by PCR from EST clones, cloned into the cloning vector pBluescript SK+ and sequenced. An expression vector for multi-cistronic cloning, based on pSCR202, was constructed and for a functional test GFP was inserted as a reporter gene. The GFP construct was transformed into Nostoc punctiforme A TCC 29133 by electroporation and expression of GFP was visualized by fluorescence microscopy. (authors)

  7. Heterologous expression of an algal hydrogenase in a hetero-cystous cyanobacterium

    International Nuclear Information System (INIS)

    Thorsten Heidorn; Peter Lindblad

    2006-01-01

    For the expression of an active algal [FeFe] hydrogenase in the hetero-cystous cyanobacterium Nostoc punctiforme A TCC 29133 the Chlamydomonas reinhardtii hydrogenase gene hydA1 and the accessory genes hydEF and hydG are to be introduced into the cyano-bacterial cells. The genes were amplified by PCR from EST clones, cloned into the cloning vector pBluescript SK+ and sequenced. An expression vector for multi-cistronic cloning, based on pSCR202, was constructed and for a functional test GFP was inserted as a reporter gene. The GFP construct was transformed into Nostoc punctiforme A TCC 29133 by electroporation and expression of GFP was visualized by fluorescence microscopy. (authors)

  8. Jizanpeptins, Cyanobacterial Protease Inhibitors from a Symploca sp. Cyanobacterium Collected in the Red Sea.

    Science.gov (United States)

    Gallegos, David A; Saurí, Josep; Cohen, Ryan D; Wan, Xuemei; Videau, Patrick; Vallota-Eastman, Alec O; Shaala, Lamiaa A; Youssef, Diaa T A; Williamson, R Thomas; Martin, Gary E; Philmus, Benjamin; Sikora, Aleksandra E; Ishmael, Jane E; McPhail, Kerry L

    2018-05-29

    Jizanpeptins A-E (1-5) are micropeptin depsipeptides isolated from a Red Sea specimen of a Symploca sp. cyanobacterium. The planar structures of the jizanpeptins were established using NMR spectroscopy and mass spectrometry and contain 3-amino-6-hydroxy-2-piperidone (Ahp) as one of eight residues in a typical micropeptin motif, as well as a side chain terminal glyceric acid sulfate moiety. The absolute configurations of the jizanpeptins were assigned using a combination of Marfey's methodology and chiral-phase HPLC analysis of hydrolysis products compared to commercial and synthesized standards. Jizanpeptins A-E showed specific inhibition of the serine protease trypsin (IC 50 = 72 nM to 1 μM) compared to chymotrypsin (IC 50 = 1.4 to >10 μM) in vitro and were not overtly cytotoxic to HeLa cervical or NCI-H460 lung cancer cell lines at micromolar concentrations.

  9. Genetic Basis for Geosmin Production by the Water Bloom-Forming Cyanobacterium, Anabaena ucrainica

    Directory of Open Access Journals (Sweden)

    Zhongjie Wang

    2014-12-01

    Full Text Available Geosmin is a common, musty-smelling sesquiterpene, principally produced by cyanobacteria. Anabaena ucrainica (Schhorb. Watanabe, a water bloom-forming cyanobacterium, is the geosmin producer responsible for odor problems in Dianchi and Erhai lakes in China. In this study, the geosmin synthase gene (geo of A. ucrainica and its flanking regions were identified and cloned by polymerase chain reaction (PCR and genome walking. The geo gene was found to be located in a transcription unit with two cyclic nucleotide-binding protein genes (cnb. The two cnb genes were highly similar and were predicted members of the cyclic adenosine monophosphate (cAMP receptor protein/fumarate nitrate reductase regulator (Crp–Fnr family. Phylogenetic and evolutionary analyses implied that the evolution of the geosmin genes involved a horizontal gene transfer process in cyanobacteria. These genes showed a close relationship to 2-methylisoborneol genes in origin and evolution.

  10. Large scale filaments associated with Milky Way spiral arms

    Science.gov (United States)

    Wang, Ke; Testi, Leonardo; Ginsburg, Adam; Walmsley, Malcolm; Molinari, Sergio; Schisano, Eugenio

    2015-08-01

    The ubiquity of filamentary structure at various scales through out the Galaxy has triggered a renewed interest in their formation, evolution, and role in star formation. The largest filaments can reach up to Galactic scale as part of the spiral arm structure. However, such large scale filaments are hard to identify systematically due to limitations in identifying methodology (i.e., as extinction features). We present a new approach to directly search for the largest, coldest, and densest filaments in the Galaxy, making use of sensitive Herschel Hi-GAL data complemented by spectral line cubes. We present a sample of the 9 most prominent Herschel filaments from a pilot search field. These filaments measure 37-99 pc long and 0.6-3.0 pc wide with masses (0.5-8.3)×104 Msun, and beam-averaged (28", or 0.4-0.7 pc) peak H2 column densities of (1.7-9.3)x1022 cm-2. The bulk of the filaments are relatively cold (17-21 K), while some local clumps have a dust temperature up to 25-47 K due to local star formation activities. All the filaments are located within spiral arm model incorporating the latest parallax measurements, we find that 7/9 of them reside within arms, but most are close to arm edges. These filaments are comparable in length to the Galactic scale height and therefore are not simply part of a grander turbulent cascade. These giant filaments, which often contain regularly spaced pc-scale clumps, are much larger than the filaments found in the Herschel Gould's Belt Survey, and they form the upper ends in the filamentary hierarchy. Full operational ALMA and NOEMA will be able to resolve and characterize similar filaments in nearby spiral galaxies, allowing us to compare the star formation in a uniform context of spiral arms.

  11. Topology of interaction between titin and myosin thick filaments.

    Science.gov (United States)

    Kellermayer, Miklós; Sziklai, Dominik; Papp, Zsombor; Decker, Brennan; Lakatos, Eszter; Mártonfalvi, Zsolt

    2018-05-05

    Titin is a giant protein spanning between the Z- and M-lines of the sarcomere. In the A-band titin is associated with the myosin thick filament. It has been speculated that titin may serve as a blueprint for thick-filament formation due to the super-repeat structure of its A-band domains. Accordingly, titin might provide a template that determines the length and structural periodicity of the thick filament. Here we tested the titin ruler hypothesis by mixing titin and myosin at in situ stoichiometric ratios (300 myosins per 12 titins) in buffers of different ionic strength (KCl concentration range 100-300 mM). The topology of the filamentous complexes was investigated with atomic force microscopy. We found that the samples contained distinct, segregated populations of titin molecules and myosin thick filaments. We were unable to identify complexes in which myosin molecules were regularly associated to either mono- or oligomeric titin in either relaxed or stretched states of the titin filaments. Thus, the electrostatically driven self-association is stronger in both myosin and titin than their binding to each other, and it is unlikely that titin functions as a geometrical template for thick-filament formation. However, when allowed to equilibrate configurationally, long myosin thick filaments appeared with titin oligomers attached to their surface. The titin meshwork formed on the thick-filament surface may play a role in controlling thick-filament length by regulating the structural dynamics of myosin molecules and placing a mechanical limit on the filament length. Copyright © 2018 Elsevier Inc. All rights reserved.

  12. Isolation and Purification of Heterotetrameric Catalase from a Desiccation Tolerant Cyanobacterium Lyngbya arboricola

    Directory of Open Access Journals (Sweden)

    Kapoor, Shivali

    2013-02-01

    Full Text Available The desiccation tolerant cyanobacterium Lyngbya arboricola, isolated from bark surfaces of Mangifera indica, possessed up to four stable isoforms of catalase in addition to other antioxidative enzymes, for several years under a dry state. Purification of the two most persistent isoforms of catalase (Cat has been undertaken by employing acetone precipitation, ethanol: chloroform treatment, gel filtration and ion exchange chromatography. The two isoforms of catalase remained almost unchanged on varying matric and osmotic hydration levels of mats of the cyanobacterium. The purification procedures resulted in a 1.3 % yield of purified single isoform (0.22 mg mL-1 protein with 709 Units mg-1 specific activity and a purity index of 0.83. Five millimolar of dithiothreitol (DTT was observed to be pertinent in maintaining the optimum redox state of the enzyme. The purification procedures additionally facilitated the simultaneous elimination and procurement of phycoerythrins (PE and mycosporine-like amino acids (MAA. Each purified isoform gave a single band (~45kDa upon SDS-PAGE and denaturing urea isoelectric focusing (IEF depicted the presence of 2 subunits each of CatA and CatB. The monoisotopic mass and pI value of CatA and CatB as revealed by LC-MS analysis and internal amino acid sequencing was 78.96, 5.89 and 80.77, 5.92, respectively, showing resemblance with CatA of Erysiphe graminis subs. hordei and CatB of Ajellomyces capsulata. The heterotetrameric monofunctional catalase (~320 kDa, due to its stability in the form of resistance to ethanol: chloroform, its thermoalkaliphilic nature and the presence of innumerable hydrophobic amino acid residues (~40%, thus exhibited its potential for biotechnological applications.

  13. Cellular responses and bioremoval of nonylphenol by the bloom-forming cyanobacterium Planktothrix agardhii 1113

    Science.gov (United States)

    Medvedeva, Nadezda; Zaytseva, Tatyana; Kuzikova, Irina

    2017-07-01

    Nonylphenol (NP) is extensively used in agricultural, industrial and household applications. Moreover, NP is the major breakdown product of the nonionic surfactants, nonylphenol ethoxylates (NPEOs), the most widely used group of surfactants. Nonylphenol is persistent in the environment, highly toxic to aquatic organisms and is a potential endocrine disruptor. NP and NPEOs have been identified as priority hazardous substances under the Environmental Quality Standards Directive 2013/39/EU and are referred to in the list of substances of particular risk to the Baltic Sea. The toxicity of NP to the bloom-forming cyanobacterium Planktothrix agardhii 1113 isolated from the eastern Gulf of Finland, Baltic Sea and the bioremoval of NP by P. agardhii were studied. NP in concentrations > 0.4 mg L- 1 suppressed cyanobacterial growth. The median effective concentration of NP for P. agardhii after 4 days of treatment (EC50) was 1.5 mg L- 1. The removal of NP from the culture medium was primarily due to abiotic processes and biodegradation by the cyanobacterium rather than sorption by the cells. NP significantly increased the photosynthetic pigments, extracellular proteins and soluble exopolysaccharides content. The cyanobacterial growth inhibition was accompanied by the increased synthesis of microcystin dm-RR and of the odorous metabolites, geosmin and 2-methylisoborneol (MIB), by P. agardhii 1113. NP also notably increased the microcystin released into the environment. Increased levels of extracellular proteins, soluble exopolysaccharides, microcystins and odorous metabolites may affect the microbial loop in aquatic ecosystems. An increased level of malondialdehyde (MDA) was indicative of the formation of free radicals in P. agardhii under NP stress, whereas increased levels of superoxide dismutase (SOD), catalase (CAT), reduced glutathione (GSH) and proline indicated the occurrence of a scavenging mechanism.

  14. Sorption and desorption studies of chromium(VI) from nonviable cyanobacterium Nostoc muscorum biomass

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, V.K. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)], E-mail: vinodfcy@iitr.ernet.in; Rastogi, A. [Department of Chemistry, Indian Institute of Technology Roorkee, Roorkee 247667 (India)

    2008-06-15

    This communication presents results pertaining to the sorptive and desorptive studies carried out on chromium(VI) removal onto nonviable freshwater cyanobacterium (Nostoc muscorum) biomass. Influence of varying the conditions for removal of chromium(VI), such as the pH of aqueous solution, the dosage of biosorbent, the contact time with the biosorbent, the temperature for the removal of chromium, the effect of light metal ions and the adsorption-desorption studies were investigated. Sorption interaction of chromium on to cyanobacterial species obeyed both the first and the second-order rate equation and the experimental data showed good fit with both the Langmuir and freundlich adsorption isotherm models. The maximum adsorption capacity was 22.92 mg/g at 25 {sup o}C and pH 3.0. The adsorption process was endothermic and the values of thermodynamic parameters of the process were calculated. Various properties of the cyanobacterium, as adsorbent, explored in the characterization part were chemical composition of the adsorbent, surface area calculation by BET method and surface functionality by FTIR. Sorption-desorption of chromium into inorganic solutions and distilled water were observed and this indicated the biosorbent could be regenerated using 0.1 M HNO{sub 3} and EDTA with upto 80% recovery. The biosorbents were reused in five biosorption-desorption cycles without a significant loss in biosorption capacity. Thus, this study demonstrated that the cyanobacterial biomass N. muscorum could be used as an efficient biosorbent for the treatment of chromium(VI) bearing wastewater.

  15. Temporal Gene Expression of the Cyanobacterium Arthrospira in Response to Gamma Rays

    Science.gov (United States)

    Badri, Hanène; Monsieurs, Pieter; Coninx, Ilse; Nauts, Robin; Wattiez, Ruddy; Leys, Natalie

    2015-01-01

    The edible cyanobacterium Arthrospira is resistant to ionising radiation. The cellular mechanisms underlying this radiation resistance are, however, still largely unknown. Therefore, additional molecular analysis was performed to investigate how these cells can escape from, protect against, or repair the radiation damage. Arthrospira cells were shortly exposed to different doses of 60Co gamma rays and the dynamic response was investigated by monitoring its gene expression and cell physiology at different time points after irradiation. The results revealed a fast switch from an active growth state to a kind of 'survival modus' during which the cells put photosynthesis, carbon and nitrogen assimilation on hold and activate pathways for cellular protection, detoxification, and repair. The higher the radiation dose, the more pronounced this global emergency response is expressed. Genes repressed during early response, suggested a reduction of photosystem II and I activity and reduced tricarboxylic acid (TCA) and Calvin-Benson-Bassham (CBB) cycles, combined with an activation of the pentose phosphate pathway (PPP). For reactive oxygen species detoxification and restoration of the redox balance in Arthrospira cells, the results suggested a powerful contribution of the antioxidant molecule glutathione. The repair mechanisms of Arthrospira cells that were immediately switched on, involve mainly proteases for damaged protein removal, single strand DNA repair and restriction modification systems, while recA was not induced. Additionally, the exposed cells showed significant increased expression of arh genes, coding for a novel group of protein of unknown function, also seen in our previous irradiation studies. This observation confirms our hypothesis that arh genes are key elements in radiation resistance of Arthrospira, requiring further investigation. This study provides new insights into phasic response and the cellular pathways involved in the radiation resistance of

  16. Temporal Gene Expression of the Cyanobacterium Arthrospira in Response to Gamma Rays.

    Directory of Open Access Journals (Sweden)

    Hanène Badri

    Full Text Available The edible cyanobacterium Arthrospira is resistant to ionising radiation. The cellular mechanisms underlying this radiation resistance are, however, still largely unknown. Therefore, additional molecular analysis was performed to investigate how these cells can escape from, protect against, or repair the radiation damage. Arthrospira cells were shortly exposed to different doses of 60Co gamma rays and the dynamic response was investigated by monitoring its gene expression and cell physiology at different time points after irradiation. The results revealed a fast switch from an active growth state to a kind of 'survival modus' during which the cells put photosynthesis, carbon and nitrogen assimilation on hold and activate pathways for cellular protection, detoxification, and repair. The higher the radiation dose, the more pronounced this global emergency response is expressed. Genes repressed during early response, suggested a reduction of photosystem II and I activity and reduced tricarboxylic acid (TCA and Calvin-Benson-Bassham (CBB cycles, combined with an activation of the pentose phosphate pathway (PPP. For reactive oxygen species detoxification and restoration of the redox balance in Arthrospira cells, the results suggested a powerful contribution of the antioxidant molecule glutathione. The repair mechanisms of Arthrospira cells that were immediately switched on, involve mainly proteases for damaged protein removal, single strand DNA repair and restriction modification systems, while recA was not induced. Additionally, the exposed cells showed significant increased expression of arh genes, coding for a novel group of protein of unknown function, also seen in our previous irradiation studies. This observation confirms our hypothesis that arh genes are key elements in radiation resistance of Arthrospira, requiring further investigation. This study provides new insights into phasic response and the cellular pathways involved in the radiation

  17. Radiation characteristics and effective optical properties of dumbbell-shaped cyanobacterium Synechocystis sp

    International Nuclear Information System (INIS)

    Heng, Ri-Liang; Pilon, Laurent

    2016-01-01

    This study presents experimental measurements of the radiation characteristics of unicellular freshwater cyanobacterium Synechocystis sp. during their exponential growth in F medium. Their scattering phase function at 633 nm average spectral absorption and scattering cross-sections between 400 and 750 nm were measured. In addition, an inverse method was used for retrieving the spectral effective complex index of refraction of overlapping or touching bispheres and quadspheres from their absorption and scattering cross-sections. The inverse method combines a genetic algorithm and a forward model based on Lorenz–Mie theory, treating bispheres and quadspheres as projected area and volume-equivalent coated spheres. The inverse method was successfully validated with numerically predicted average absorption and scattering cross-sections of suspensions consisting of bispheres and quadspheres, with realistic size distributions, using the T-matrix method. It was able to retrieve the monomers' complex index of refraction with size parameter up to 11, relative refraction index less than 1.3, and absorption index less than 0.1. Then, the inverse method was applied to retrieve the effective spectral complex index of refraction of Synechocystis sp. approximated as randomly oriented aggregates consisting of two overlapping homogeneous spheres. Both the measured absorption cross-section and the retrieved absorption index featured peaks at 435 and 676 nm corresponding to chlorophyll a, a peak at 625 nm corresponding to phycocyanin, and a shoulder around 485 nm corresponding to carotenoids. These results can be used to optimize and control light transfer in photobioreactors. The inverse method and the equivalent coated sphere model could be applied to other optically soft particles of similar morphologies. - Highlights: • Radiation characteristics of Synechocystis sp. were measured during exponential growth. • This unicellular freshwater cyanobacterium features an interesting

  18. First report of neurotoxic effect of the cyanobacterium Cylindrospermopsis raciborskii on the motility of trematode metacercariae.

    Science.gov (United States)

    Lopes, K C; Ferrão-Filho, A S; Santos, E G N; Santos, C P

    2018-03-01

    Cylindrospermopsis raciborskii (Woloszynska) is a photosynthetic cyanobacterium that can produce cytotoxic (cylindrospermopsin) and neurotoxic cyanotoxins (saxitoxins). In Brazil the strains of C. raciborskii are reported to produce only saxitoxins (STX) and their effect on fish parasites has not been tested to date. The fish Poecilia vivipara Bloch and Schneider is a common host for the trematode Pygidiopsis macrostomum Travassos off the coast of Rio de Janeiro, and this fish-parasite interaction is a model for behavioural and ecotoxicological studies. The aim of this work was to evaluate the motility of metacercariae of P. macrostomum from P. vivipara exposed to 40 mg l-1 and 400 mg l-1 of crude lyophilized extract of the cyanobacterium C. raciborskii (CYRF-01) for 48 h. The fish were separated into groups of ten individuals and, after exposure, five fish from each group were dissected for counting and checking the motility of metacercariae. The other five fish were dissected after 48 h in clean water. The detection and quantification of STX in the solutions of cyanobacteria, and the gills and guts of fish, were performed by an enzyme-linked immunosorbent assay. The crude extract of C. raciborskii caused temporary paralysis in metacercariae of P. macrostomum after exposure of fish to both concentrations, and the motility recovered after the fish were kept for 48 h in clean water. STX was detected in the guts and gills of all fish analysed, suggesting that this toxin is involved in the paralysis of metacercariae. This is the first report on the action of neurotoxins in metacercariae of fish.

  19. Physical principles of filamentous protein self-assembly kinetics

    International Nuclear Information System (INIS)

    Michaels, Thomas C T; Liu, Lucie X; Meisl, Georg; Knowles, Tuomas P J

    2017-01-01

    The polymerization of proteins and peptides into filamentous supramolecular structures is an elementary form of self-organization of key importance to the functioning biological systems, as in the case of actin biofilaments that compose the cellular cytoskeleton. Aberrant filamentous protein self-assembly, however, is associated with undesired effects and severe clinical disorders, such as Alzheimer’s and Parkinson’s diseases, which, at the molecular level, are associated with the formation of certain forms of filamentous protein aggregates known as amyloids. Moreover, due to their unique physicochemical properties, protein filaments are finding extensive applications as biomaterials for nanotechnology. With all these different factors at play, the field of filamentous protein self-assembly has experienced tremendous activity in recent years. A key question in this area has been to elucidate the microscopic mechanisms through which filamentous aggregates emerge from dispersed proteins with the goal of uncovering the underlying physical principles. With the latest developments in the mathematical modeling of protein aggregation kinetics as well as the improvement of the available experimental techniques it is now possible to tackle many of these complex systems and carry out detailed analyses of the underlying microscopic steps involved in protein filament formation. In this paper, we review some classical and modern kinetic theories of protein filament formation, highlighting their use as a general strategy for quantifying the molecular-level mechanisms and transition states involved in these processes. (topical review)

  20. Fully filamentized HTS coated conductor via striation and selective electroplating

    Energy Technology Data Exchange (ETDEWEB)

    Kesgin, Ibrahim; Majkic, Goran [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States); Selvamanickam, Venkat, E-mail: selva@uh.edu [Department of Mechanical Engineering and Texas Center for Superconductivity, University of Houston, Houston, TX 77204 (United States)

    2013-03-15

    Highlights: ► Fully-filamentized coated conductor with 13-fold reduction in ac losses. ► Selective electroplating for filamentization of thick copper stabilizer. ► A twofold decrease in ac loss by filamentization of copper stabilizer. ► Absence of appreciable coupling loss contribution from electroplating. -- Abstract: A simple, cost-effective method involving top-down mechanical scribing, oxidation and bottom-up electroplating has been successfully developed to fabricate fully filamentized HTS coated conductors. The copper stabilizer layer is selectively electroplated on the superconducting filaments while the striations remain copper-free due to the formation of a resistive oxide layer in between filaments by oxidation of the striated grooves at elevated temperature in oxygen atmosphere. Magnetization AC loss measurements, performed in a frequency range of 45–500 Hz at 77 K, confirmed the expected N-fold reduction in AC loss of the filamentized tapes with no significant degradation in critical current beyond that due to the material removal from the striations (N – number of filaments). A considerable reduction in coupling AC loss was observed after high temperature annealing/oxidation of the striated tapes. Furthermore, a significant reduction in eddy current loss was achieved with selective copper electroplating, as evidenced by analyzing the field and frequency dependence of magnetization AC loss, as well as by comparing the AC loss performance of striated samples to that of non-striated samples after electroplating of copper stabilizer.

  1. Filament bundle location influence on coupling losses in superconducting composites

    International Nuclear Information System (INIS)

    Ito, Daisuke; Koizumi, Misao; Hamajima, Takataro; Nakane, Fumoto.

    1983-01-01

    The ac losses in multifilamentary superconducting composites with different superconducting filament bundle positions have been measured using the magnetization method in order to reveal the relation between filament bundle position and coupling losses. Loss components depending on dB/dt in a mixed matrix superconducting composite, whose filament bundle is located in a central region surrounded by an outer stabilizing copper sheath, has been compared with another superconducting composite whose stabilizing copper is located in a central region surrounded by an outer filament bundle. In both conductors, key parameters, such as filament twistpitch, wire diameter and amount of copper stabilizer, were almost the same. Applied magnetic field is 2 Tesla with 0.05-2 Tesla/sec field change rate. Experimental results indicate that coupling losses between filaments in the composite with the filament bundle located in the central region is smaller than the composite with the filament bundle located in the outer region. A similar conclusion was reached theoretically by B. Truck. Coupling loss values obtained by the experiment show good agreement with calculated values with the equations proposed by B. Truck. It is also pointed out that a copper stabilizer, divided by the CuNi barrier into small regions, like a honeycomb, causes anomalous increasing in the copper resistivity due to Ni diffusion during heat treatment. (author)

  2. THE APPARATUS FOR ALIGNMENT OF THE PHOTOMETRIC LAMP FILAMENT

    Directory of Open Access Journals (Sweden)

    V. A. Dlugunovich

    2015-01-01

    Full Text Available During photometric measurements involving the use of photometric lamps it is necessary that the filament of lamp takes a strictly predetermined position with respect to the photodetector and the optical axis of the photometric setup. The errors in positioning of alignment filament with respect to the optical axis of the measuring system lead to increase the uncertainty of measurement of the photometric characteristics of the light sources. A typical method for alignment of filament of photometric lamps is based on the use a diopter tubes (telescopes. Using this method, the mounting of filament to the required position is carried out by successive approximations, which requires special concentration and a lot of time. The aim of this work is to develop an apparatus for alignment which allows simultaneous alignment of the filament of lamps in two mutually perpendicular planes. The method and apparatus for alignment of the photometric lamp filament during measurements of the photometric characteristics of light sources based on two digital video cameras is described in this paper. The apparatus allows to simultaneously displaying the image of lamps filament on the computer screen in two mutually perpendicular planes. The apparatus eliminates a large number of functional units requiring elementwise alignment and reduces the time required to carry out the alignment. The apparatus also provides the imaging of lamps filament with opaque coated on the bulb. The apparatus is used at the National standard of light intensity and illuminance units of the Republic of Belarus. 

  3. Method for simultaneously coating a plurality of filaments

    Science.gov (United States)

    Miller, P.A.; Pochan, P.D.; Siegal, M.P.; Dominguez, F.

    1995-07-11

    Methods and apparatuses are disclosed for coating materials, and the products and compositions produced thereby. Substances, such as diamond or diamond-like carbon, are deposited onto materials, such as a filament or a plurality of filaments simultaneously, using one or more cylindrical, inductively coupled, resonator plasma reactors. 3 figs.

  4. Accurate simulation dynamics of microscopic filaments using "caterpillar" Oseen hydrodynamics

    NARCIS (Netherlands)

    Bailey, A.G.; Lowe, C.P.; Pagonabarraga, I.; Cosentino Lagomarsino, M.

    2009-01-01

    Microscopic semiflexible filaments suspended in a viscous fluid are widely encountered in biophysical problems. The classic example is the flagella used by microorganisms to generate propulsion. Simulating the dynamics of these filaments numerically is complicated because of the coupling between the

  5. Process for the production of superconductor containing filaments

    Energy Technology Data Exchange (ETDEWEB)

    Tuominen, Olli P. (Candler, NC); Hoyt, Matthew B. (Arden, NC); Mitchell, David F. (Asheville, NC); Morgan, Carol W. (Asheville, NC); Roberts, Clyde Gordon (Asheville, NC); Tyler, Robert A. (Canton, NC)

    2002-01-01

    Superconductor containing filaments having embedments of superconducting material surrounded by a rayon matrix are formed by preparing a liquid suspension which contains at least 10 weight percent superconducting material; forming a multicomponent filament having a core of the suspension and a viscose sheath which contains cellulose xanthate; and thereafter, regenerating cellulose from the cellulose xanthate to form a rayon matrix.

  6. Design and Optimization of Filament Wound Composite Pressure Vessels

    NARCIS (Netherlands)

    Zu, L.

    2012-01-01

    One of the most important issues for the design of filament-wound pressure vessels reflects on the determination of the most efficient meridian profiles and related fiber architectures, leading to optimal structural performance. To better understand the design and optimization of filament-wound

  7. Physical principles of filamentous protein self-assembly kinetics

    Science.gov (United States)

    Michaels, Thomas C. T.; Liu, Lucie X.; Meisl, Georg; Knowles, Tuomas P. J.

    2017-04-01

    The polymerization of proteins and peptides into filamentous supramolecular structures is an elementary form of self-organization of key importance to the functioning biological systems, as in the case of actin biofilaments that compose the cellular cytoskeleton. Aberrant filamentous protein self-assembly, however, is associated with undesired effects and severe clinical disorders, such as Alzheimer’s and Parkinson’s diseases, which, at the molecular level, are associated with the formation of certain forms of filamentous protein aggregates known as amyloids. Moreover, due to their unique physicochemical properties, protein filaments are finding extensive applications as biomaterials for nanotechnology. With all these different factors at play, the field of filamentous protein self-assembly has experienced tremendous activity in recent years. A key question in this area has been to elucidate the microscopic mechanisms through which filamentous aggregates emerge from dispersed proteins with the goal of uncovering the underlying physical principles. With the latest developments in the mathematical modeling of protein aggregation kinetics as well as the improvement of the available experimental techniques it is now possible to tackle many of these complex systems and carry out detailed analyses of the underlying microscopic steps involved in protein filament formation. In this paper, we review some classical and modern kinetic theories of protein filament formation, highlighting their use as a general strategy for quantifying the molecular-level mechanisms and transition states involved in these processes.

  8. Hydrodynamic interaction induced spontaneous rotation of coupled active filaments.

    Science.gov (United States)

    Jiang, Huijun; Hou, Zhonghuai

    2014-12-14

    We investigate the coupled dynamics of active filaments with long range hydrodynamic interactions (HI). Remarkably, we find that filaments can rotate spontaneously under the same conditions in which a single filament alone can only move in translation. Detailed analysis reveals that the emergence of coupled rotation originates from an asymmetric flow field associated with HI which breaks the symmetry of translational motion when filaments approach. The breaking is then further stabilized by HI to form self-sustained coupled rotation. Intensive simulations show that coupled rotation forms easily when one filament tends to collide with the front-half of the other. For head-to-tail approaching, we observe another interesting HI-induced coupled motion, where filaments move together in the form of one following the other. Moreover, the radius of coupled rotation increases exponentially as the rigidity of the filament increases, which suggests that HI are also important for the alignment of rigid-rod-like filaments which has been assumed to be solely a consequence of direct collisions.

  9. Thick Filament Protein Network, Functions, and Disease Association.

    Science.gov (United States)

    Wang, Li; Geist, Janelle; Grogan, Alyssa; Hu, Li-Yen R; Kontrogianni-Konstantopoulos, Aikaterini

    2018-03-13

    Sarcomeres consist of highly ordered arrays of thick myosin and thin actin filaments along with accessory proteins. Thick filaments occupy the center of sarcomeres where they partially overlap with thin filaments. The sliding of thick filaments past thin filaments is a highly regulated process that occurs in an ATP-dependent manner driving muscle contraction. In addition to myosin that makes up the backbone of the thick filament, four other proteins which are intimately bound to the thick filament, myosin binding protein-C, titin, myomesin, and obscurin play important structural and regulatory roles. Consistent with this, mutations in the respective genes have been associated with idiopathic and congenital forms of skeletal and cardiac myopathies. In this review, we aim to summarize our current knowledge on the molecular structure, subcellular localization, interacting partners, function, modulation via posttranslational modifications, and disease involvement of these five major proteins that comprise the thick filament of striated muscle cells. © 2018 American Physiological Society. Compr Physiol 8:631-709, 2018. Copyright © 2018 American Physiological Society. All rights reserved.

  10. A catalytic oligomeric motor that walks along a filament track

    Science.gov (United States)

    Huang, Mu-Jie; Kapral, Raymond

    2015-06-01

    Most biological motors in the cell execute chemically powered conformational changes as they walk on biopolymer filaments in order to carry out directed transport functions. Synthetic motors that operate in a similar manner are being studied since they have the potential to perform similar tasks in a variety of applications. In this paper, a synthetic nanomotor that moves along a filament track, without invoking motor conformational changes, is constructed and its properties are studied in detail. The motor is an oligomer comprising three linked beads with specific binding properties. The filament track is a stiff polymer chain, also described by a linear chain of linked coarse-grained molecular groups modeled as beads. Reactions on the filament that are catalyzed by a motor bead and use fuel in the environment, in conjunction within the binding affinities of the motor beads to the filament beads, lead to directed motion. The system operates out of equilibrium due to the state of the filament and supply of fuel. The motor, filament, and surrounding medium are all described at microscopic level that permits a full analysis of the motor motion. A stochastic model that captures the main trends seen in the simulations is also presented. The results of this study point to some of the key features that could be used to construct nanomotors that undergo biased walks powered by chemical reactions on filaments.

  11. A catalytic oligomeric motor that walks along a filament track

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Mu-Jie, E-mail: mjhuang@chem.utoronto.ca; Kapral, Raymond, E-mail: rkapral@chem.utoronto.ca [Chemical Physics Theory Group, Department of Chemistry, University of Toronto, Toronto, Ontario M5S 3H6 (Canada)

    2015-06-28

    Most biological motors in the cell execute chemically powered conformational changes as they walk on biopolymer filaments in order to carry out directed transport functions. Synthetic motors that operate in a similar manner are being studied since they have the potential to perform similar tasks in a variety of applications. In this paper, a synthetic nanomotor that moves along a filament track, without invoking motor conformational changes, is constructed and its properties are studied in detail. The motor is an oligomer comprising three linked beads with specific binding properties. The filament track is a stiff polymer chain, also described by a linear chain of linked coarse-grained molecular groups modeled as beads. Reactions on the filament that are catalyzed by a motor bead and use fuel in the environment, in conjunction within the binding affinities of the motor beads to the filament beads, lead to directed motion. The system operates out of equilibrium due to the state of the filament and supply of fuel. The motor, filament, and surrounding medium are all described at microscopic level that permits a full analysis of the motor motion. A stochastic model that captures the main trends seen in the simulations is also presented. The results of this study point to some of the key features that could be used to construct nanomotors that undergo biased walks powered by chemical reactions on filaments.

  12. Fully filamentized HTS coated conductor via striation and selective electroplating

    International Nuclear Information System (INIS)

    Kesgin, Ibrahim; Majkic, Goran; Selvamanickam, Venkat

    2013-01-01

    Highlights: ► Fully-filamentized coated conductor with 13-fold reduction in ac losses. ► Selective electroplating for filamentization of thick copper stabilizer. ► A twofold decrease in ac loss by filamentization of copper stabilizer. ► Absence of appreciable coupling loss contribution from electroplating. -- Abstract: A simple, cost-effective method involving top-down mechanical scribing, oxidation and bottom-up electroplating has been successfully developed to fabricate fully filamentized HTS coated conductors. The copper stabilizer layer is selectively electroplated on the superconducting filaments while the striations remain copper-free due to the formation of a resistive oxide layer in between filaments by oxidation of the striated grooves at elevated temperature in oxygen atmosphere. Magnetization AC loss measurements, performed in a frequency range of 45–500 Hz at 77 K, confirmed the expected N-fold reduction in AC loss of the filamentized tapes with no significant degradation in critical current beyond that due to the material removal from the striations (N – number of filaments). A considerable reduction in coupling AC loss was observed after high temperature annealing/oxidation of the striated tapes. Furthermore, a significant reduction in eddy current loss was achieved with selective copper electroplating, as evidenced by analyzing the field and frequency dependence of magnetization AC loss, as well as by comparing the AC loss performance of striated samples to that of non-striated samples after electroplating of copper stabilizer

  13. Biophysics of filament length regulation by molecular motors

    International Nuclear Information System (INIS)

    Kuan, Hui-Shun; Betterton, M D

    2013-01-01

    Regulating physical size is an essential problem that biological organisms must solve from the subcellular to the organismal scales, but it is not well understood what physical principles and mechanisms organisms use to sense and regulate their size. Any biophysical size-regulation scheme operates in a noisy environment and must be robust to other cellular dynamics and fluctuations. This work develops theory of filament length regulation inspired by recent experiments on kinesin-8 motor proteins, which move with directional bias on microtubule filaments and alter microtubule dynamics. Purified kinesin-8 motors can depolymerize chemically-stabilized microtubules. In the length-dependent depolymerization model, the rate of depolymerization tends to increase with filament length, because long filaments accumulate more motors at their tips and therefore shorten more quickly. When balanced with a constant filament growth rate, this mechanism can lead to a fixed polymer length. However, the mechanism by which kinesin-8 motors affect the length of dynamic microtubules in cells is less clear. We study the more biologically realistic problem of microtubule dynamic instability modulated by a motor-dependent increase in the filament catastrophe frequency. This leads to a significant decrease in the mean filament length and a narrowing of the filament length distribution. The results improve our understanding of the biophysics of length regulation in cells. (paper)

  14. Fossil evidence for spin alignment of SDSS galaxies in filaments

    NARCIS (Netherlands)

    Jones, Bernard J.T.; Weygaert, Rien van de; Arag´on-Calvo, Miguel A.

    2010-01-01

    We search for and find fossil evidence that the distribution of the spin axes of galaxies in cosmic web filaments relative to their host filaments are not randomly distributed. This would indicate that the action of large scale tidal torques effected the alignments of galaxies located in cosmic

  15. Avian influenza a virus budding morphology: spherical or filamentous?

    Science.gov (United States)

    Most strains of influenza A virus (IAV) can produce long (µm length) filamentous virus particles as well as ~100 nm diameter spherical virions. The function of the filamentous particles is unclear but is hypothesized to facilitate transmission within or from the respiratory tract. In mammalian IAVs,...

  16. A catalytic oligomeric motor that walks along a filament track

    International Nuclear Information System (INIS)

    Huang, Mu-Jie; Kapral, Raymond

    2015-01-01

    Most biological motors in the cell execute chemically powered conformational changes as they walk on biopolymer filaments in order to carry out directed transport functions. Synthetic motors that operate in a similar manner are being studied since they have the potential to perform similar tasks in a variety of applications. In this paper, a synthetic nanomotor that moves along a filament track, without invoking motor conformational changes, is constructed and its properties are studied in detail. The motor is an oligomer comprising three linked beads with specific binding properties. The filament track is a stiff polymer chain, also described by a linear chain of linked coarse-grained molecular groups modeled as beads. Reactions on the filament that are catalyzed by a motor bead and use fuel in the environment, in conjunction within the binding affinities of the motor beads to the filament beads, lead to directed motion. The system operates out of equilibrium due to the state of the filament and supply of fuel. The motor, filament, and surrounding medium are all described at microscopic level that permits a full analysis of the motor motion. A stochastic model that captures the main trends seen in the simulations is also presented. The results of this study point to some of the key features that could be used to construct nanomotors that undergo biased walks powered by chemical reactions on filaments

  17. Beam wandering of femtosecond laser filament in air.

    Science.gov (United States)

    Yang, Jing; Zeng, Tao; Lin, Lie; Liu, Weiwei

    2015-10-05

    The spatial wandering of a femtosecond laser filament caused by the filament heating effect in air has been studied. An empirical formula has also been derived from the classical Karman turbulence model, which determines quantitatively the displacement of the beam center as a function of the propagation distance and the effective turbulence structure constant. After fitting the experimental data with this formula, the effective turbulence structure constant has been estimated for a single filament generated in laboratory environment. With this result, one may be able to estimate quantitatively the displacement of a filament over long distance propagation and interpret the practical performance of the experiments assisted by femtosecond laser filamentation, such as remote air lasing, pulse compression, high order harmonic generation (HHG), etc.

  18. Methods for genetic transformation of filamentous fungi.

    Science.gov (United States)

    Li, Dandan; Tang, Yu; Lin, Jun; Cai, Weiwen

    2017-10-03

    Filamentous fungi have been of great interest because of their excellent ability as cell factories to manufacture useful products for human beings. The development of genetic transformation techniques is a precondition that enables scientists to target and modify genes efficiently and may reveal the function of target genes. The method to deliver foreign nucleic acid into cells is the sticking point for fungal genome modification. Up to date, there are some general methods of genetic transformation for fungi, including protoplast-mediated transformation, Agrobacterium-mediated transformation, electroporation, biolistic method and shock-wave-mediated transformation. This article reviews basic protocols and principles of these transformation methods, as well as their advantages and disadvantages.

  19. Linear viscoelastic characterization from filament stretching rheometry

    DEFF Research Database (Denmark)

    Wingstrand, Sara Lindeblad; Alvarez, Nicolas J.; Hassager, Ole

    to measure both linear and nonlinear dynamics on a single apparatus. With a software modification to the FSR motor control, we show that linear viscoelasticity can be measured via small amplitude squeeze flow (SASF). Squeeze flow is a combination of both shear and extensional flow applied by axially......Traditionally, linear viscoelasticity is measured using small amplitude oscillatory shear flow. Due to experimental difficulties, shear flows are predominately confined to the linear and mildly nonlinear regime. On the other hand, extensional flows have proven more practical in measuring...... viscoelasticity well into the nonlinear regime. Therefore at present, complete rheological characterization of a material requires two apparatuses: a shear and an extensional rheometer. This work is focused on developing a linear viscoelastic protocol for the filament stretching rheometer (FSR) in order...

  20. Bursting of filaments in the plasma focus

    International Nuclear Information System (INIS)

    Gratton, F.T.L.

    1976-01-01

    Photographs of the current sheath of (low energy) plasma focus show a disruption of the filaments. This phenomenon is interpreted as a vortex breakdown. Physical parameters which support this hypothesis are obtained from measurements, from the theoretical thickness of the current sheath given by Nardi and from some models of the plasma flow. The widening of a vortex due to axial velocity increase is analyzed by means of magnetohydrodynamic collinear models. The main results are: (1) the existence of a limit separating supercritical from subcritical regimes (their character changes with the ratio between kinetic and magnetic energy); (2) the existence of flow regimes where the vortex radius remains approximately constant for moderate increments of the external velocity; (3) the structure of the vortex may change substantially for a sufficiently large increment of the external velocity, even in subcritical states; (4) the possibility that a burst of the vortex may occur when the external velocity suffers a slowdown

  1. Current filaments in turbulent magnetized plasmas

    DEFF Research Database (Denmark)

    Martines, E.; Vianello, N.; Sundkvist, D.

    2009-01-01

    gradient region of a fusion plasma confined in reversed field pinch configuration and in a density gradient region in the Earth magnetosphere are measured and compared, showing that in both environments they can be attributed to drift-Alfvén vortices. Current structures associated with reconnection events......Direct measurements of current density perturbations associated with non-linear phenomena in magnetized plasmas can be carried out using in situ magnetic measurements. In this paper we report such measurements for three different kinds of phenomena. Current density fluctuations in the edge density...... measured in a reversed field pinch plasma and in the magnetosheath are detected and compared. Evidence of current filaments occurring during ELMs in an H-mode tokamak plasma is displayed....

  2. Filament wound data base development, revision 1

    Science.gov (United States)

    Sharp, R. Scott; Braddock, William F.

    1985-01-01

    The objective was to update the present Space Shuttle Solid Rocket Booster (SRB) baseline reentry aerodynamic data base and to develop a new reentry data base for the filament wound case SRB along with individual protuberance increments. Lockheed's procedures for performing these tasks are discussed. Free fall of the SRBs after separation from the Space Shuttle Launch Vehicle is completely uncontrolled. However, the SRBs must decelerate to a velocity and attitude that is suitable for parachute deployment. To determine the SRB reentry trajectory parameters, including the rate of deceleration and attitude history during free-fall, engineers at Marshall Space Flight Center are using a six-degree-of-freedom computer program to predict dynamic behavior. Static stability aerodynamic coefficients are part of the information required for input into this computer program. Lockheed analyzed the existing reentry aerodynamic data tape (Data Tape 5) for the current steel case SRB. This analysis resulted in the development of Data Tape 7.

  3. Natural Fiber Filament Wound Composites: A Review

    Directory of Open Access Journals (Sweden)

    Mohamed Ansari Suriyati

    2017-01-01

    Full Text Available In recent development, natural fibers have attracted the interest of engineers, researchers, professionals and scientists all over the world as an alternative reinforcement for fiber reinforced polymer composites. This is due to its superior properties such as high specific strength, low weight, low cost, fairly good mechanical properties, non-abrasive, eco-friendly and bio-degradable characteristics. In this point of view, natural fiber-polymer composites (NFPCs are becoming increasingly utilized in a wide variety of applications because they represent an ecological and inexpensive alternative to conventional petroleum-derived materials. On the other hand, considerable amounts of organic waste and residue from the industrial and agricultural processes are still underutilized as low-value energy sources. This is a comprehensive review discussing about natural fiber reinforced composite produced by filament winding technique.

  4. HIERARCHICAL FRAGMENTATION OF THE ORION MOLECULAR FILAMENTS

    International Nuclear Information System (INIS)

    Takahashi, Satoko; Ho, Paul T. P.; Su, Yu-Nung; Teixeira, Paula S.; Zapata, Luis A.

    2013-01-01

    We present a high angular resolution map of the 850 μm continuum emission of the Orion Molecular Cloud-3 (OMC 3) obtained with the Submillimeter Array (SMA); the map is a mosaic of 85 pointings covering an approximate area of 6.'5 × 2.'0 (0.88 × 0.27 pc). We detect 12 spatially resolved continuum sources, each with an H 2 mass between 0.3-5.7 M ☉ and a projected source size between 1400-8200 AU. All the detected sources are on the filamentary main ridge (n H 2 ≥10 6 cm –3 ), and analysis based on the Jeans theorem suggests that they are most likely gravitationally unstable. Comparison of multi-wavelength data sets indicates that of the continuum sources, 6/12 (50%) are associated with molecular outflows, 8/12 (67%) are associated with infrared sources, and 3/12 (25%) are associated with ionized jets. The evolutionary status of these sources ranges from prestellar cores to protostar phase, confirming that OMC-3 is an active region with ongoing embedded star formation. We detect quasi-periodical separations between the OMC-3 sources of ≈17''/0.035 pc. This spatial distribution is part of a large hierarchical structure that also includes fragmentation scales of giant molecular cloud (≈35 pc), large-scale clumps (≈1.3 pc), and small-scale clumps (≈0.3 pc), suggesting that hierarchical fragmentation operates within the Orion A molecular cloud. The fragmentation spacings are roughly consistent with the thermal fragmentation length in large-scale clumps, while for small-scale cores it is smaller than the local fragmentation length. These smaller spacings observed with the SMA can be explained by either a helical magnetic field, cloud rotation, or/and global filament collapse. Finally, possible evidence for sequential fragmentation is suggested in the northern part of the OMC-3 filament.

  5. Intermediate filament protein evolution and protists.

    Science.gov (United States)

    Preisner, Harald; Habicht, Jörn; Garg, Sriram G; Gould, Sven B

    2018-03-23

    Metazoans evolved from a single protist lineage. While all eukaryotes share a conserved actin and tubulin-based cytoskeleton, it is commonly perceived that intermediate filaments (IFs), including lamin, vimentin or keratin among many others, are restricted to metazoans. Actin and tubulin proteins are conserved enough to be detectable across all eukaryotic genomes using standard phylogenetic methods, but IF proteins, in contrast, are notoriously difficult to identify by such means. Since the 1950s, dozens of cytoskeletal proteins in protists have been identified that seemingly do not belong to any of the IF families described for metazoans, yet, from a structural and functional perspective fit criteria that define metazoan IF proteins. Here, we briefly review IF protein discovery in metazoans and the implications this had for the definition of this protein family. We argue that the many cytoskeletal and filament-forming proteins of protists should be incorporated into a more comprehensive picture of IF evolution by aligning it with the recent identification of lamins across the phylogenetic diversity of eukaryotic supergroups. This then brings forth the question of how the diversity of IF proteins has unfolded. The evolution of IF proteins likely represents an example of convergent evolution, which, in combination with the speed with which these cytoskeletal proteins are evolving, generated their current diversity. IF proteins did not first emerge in metazoa, but in protists. Only the emergence of cytosolic IF proteins that appear to stem from a nuclear lamin is unique to animals and coincided with the emergence of true animal multicellularity. © 2018 Wiley Periodicals, Inc.

  6. Bundling of elastic filaments induced by hydrodynamic interactions

    Science.gov (United States)

    Man, Yi; Page, William; Poole, Robert J.; Lauga, Eric

    2017-12-01

    Peritrichous bacteria swim in viscous fluids by rotating multiple helical flagellar filaments. As the bacterium swims forward, all its flagella rotate in synchrony behind the cell in a tight helical bundle. When the bacterium changes its direction, the flagellar filaments unbundle and randomly reorient the cell for a short period of time before returning to their bundled state and resuming swimming. This rapid bundling and unbundling is, at its heart, a mechanical process whereby hydrodynamic interactions balance with elasticity to determine the time-varying deformation of the filaments. Inspired by this biophysical problem, we present in this paper what is perhaps the simplest model of bundling whereby two or more straight elastic filaments immersed in a viscous fluid rotate about their centerline, inducing rotational flows which tend to bend the filaments around each other. We derive an integrodifferential equation governing the shape of the filaments resulting from mechanical balance in a viscous fluid at low Reynolds number. We show that such equation may be evaluated asymptotically analytically in the long-wavelength limit, leading to a local partial differential equation governed by a single dimensionless bundling number. A numerical study of the dynamics predicted by the model reveals the presence of two configuration instabilities with increasing bundling numbers: first to a crossing state where filaments touch at one point and then to a bundled state where filaments wrap along each other in a helical fashion. We also consider the case of multiple filaments and the unbundling dynamics. We next provide an intuitive physical model for the crossing instability and show that it may be used to predict analytically its threshold and adapted to address the transition to a bundling state. We then use a macroscale experimental implementation of the two-filament configuration in order to validate our theoretical predictions and obtain excellent agreement. This long

  7. Resistance to the photosystem II herbicide diuron is dominant to sensitivity in the cyanobacterium Synechococcus sp. PCC7942

    OpenAIRE

    Brusslan, Judy; Haselkorn, Robert

    1989-01-01

    The transformable cyanobacterium, Synechococcus sp. PCC7942, was used to study the genetics of resistance to the herbicide diuron. In wild-type cells, diuron binds to one of the core proteins, called D1, of photosystem II reaction centres. This binding prevents the transfer of electrons from QA, the primary quinone acceptor, to QB, which is necessary to create the charge separation that drives ATP synthesis. A single amino acid substitution in the D1 protein reduces diuron binding and confers...

  8. Identification of the n-1 fatty acid as an antibacterial constituent from the edible freshwater cyanobacterium Nostoc verrucosum.

    Science.gov (United States)

    Oku, Naoya; Yonejima, Kohsuke; Sugawa, Takao; Igarashi, Yasuhiro

    2014-01-01

    The cyanobacterium Nostoc verrucosum occurs in cool, clear streams and its gelatinous colonies, called "ashitsuki," have been eaten in ancient Japan. Its ethanolic extract was found to inhibit the growth of Gram-positive bacteria and activity-guided fractionation yielded an unusual n-1 fatty acid, (9Z,12Z)-9,12,15-hexadecatrienoic acid (1), as one of the active principles. It inhibited the growth of Staphylococcus aureus at MIC 64 μg/mL.

  9. Discovery of Rare and Highly Toxic Microcystins from Lichen-Associated Cyanobacterium Nostoc sp. Strain IO-102-I

    OpenAIRE

    Oksanen, Ilona; Jokela, Jouni; Fewer, David P.; Wahlsten, Matti; Rikkinen, Jouko; Sivonen, Kaarina

    2004-01-01

    The production of hepatotoxic cyclic heptapeptides, microcystins, is almost exclusively reported from planktonic cyanobacteria. Here we show that a terrestrial cyanobacterium Nostoc sp. strain IO-102-I isolated from a lichen association produces six different microcystins. Microcystins were identified with liquid chromatography-UV mass spectrometry by their retention times, UV spectra, mass fragmentation, and comparison to microcystins from the aquatic Nostoc sp. strain 152. The dominant micr...

  10. Short Communication: Effects of temperature on growth, pigment composition and protein content of an Antarctic Cyanobacterium Nostoc commune

    Directory of Open Access Journals (Sweden)

    RANJANA TRIPATHI

    2012-11-01

    Full Text Available Tripathi R, Dhuldhaj UP, Singh S. 2012. Short Communication: Effects of temperature on growth, pigment composition and protein content of an Antarctic Cyanobacterium Nostoc commune. Nusantara Bioscience 4: 134-137. Effect of temperature variation on biomass accumulation, pigment composition and protein content were studied for the cyanobacterium Nostoc commune, isolated from Antarctica. Results confirmed the psychrotrophic behavior (optimum growth temperature 25◦C of the cyanobacterium. Low temperature increased the duration of lag phase and exponential growth phase. Maximum increase in biomass was recorded on 24th day at 25◦C and on 12th day at 50C. The downshift from 25 to 5◦C had almost negligible effect on chl a content. Maximal protein content was recorded for cultures growing at 50C on 12th day. The carotenoids/chl a ratio was maximum (2.48 at 50C on 9th day. It remained almost constant for cultures growing at 5 and 350C. There was an induction in protein synthesis following downshift in temperature from 25 to 5◦C.

  11. Footpoint detection and mass-motion in chromospheric filaments

    Science.gov (United States)

    V, Aparna; Hardersen, P. S.; Martin, S. F.

    2013-07-01

    A quiescent region on the Sun containing three filaments is used to study the properties of mass motion. This study determines if the footpoints or end-points of the filaments are the locations from where mass gets injected into the filaments. Several hypotheses have been put forth in the past to determine how a filament acquires mass. Trapping of coronal mass in the filament channel due to condensation (Martin, 1996) and injection of mass into the filaments during magnetic reconnection (Priest, et al., 1995) are some of the speculations. This study looks for indications for injection of mass via chromospheric footpoints. The data consists of blue (Hα-0.5 Å) and red (Hα+0.5 Å) wing high resolution Hα images of the W29N37 region of the Sun taken on Oct 30, 2010, from 1200 - 1600 UT. The Dutch Open Telescope was used to obtain the data. The images are aligned and animated to see Doppler motion in the fibrils. Smaller fibrils merge to form longer ones; barbs appear and disappear in one of the long filaments and is seen moving along the length of the filament. A region with no typical filament-like absorption feature is observed to be continuously receiving mass. Fibrils appear to be converging from opposite sides along what appears to be a neutral line; mass motion is seen in these fibrils as well. An eruption occurs in a region of fibrils lumped together at the end of the first hour (1300 UT) followed by plage brightening at 1430 UT near one of the filament regions. Helioviewer (Panasenco, et al., 2011) is used for aligning the images; GIMP is used for precision alignment and animation. Each frame in the sequence is studied carefully to note changes in the filament regions. The footpoints of the filaments are determined by the changes observed in the position of the filament ‘legs’ in each frame. Variations in the magnetic polarity corresponding to changes observed in the chromosphere are analyzed using HMI magnetograms. Bright and dark points on the

  12. Microwave structure of quiescent solar filaments at high resolution

    International Nuclear Information System (INIS)

    Gary, D.E.

    1986-01-01

    High resolution very low altitude maps of a quiescent filament at three frequencies are presented. The spatial resolution (approx. 15'' at 1.45 GHz, approx. 6'' at 4.9 GHz, and approx. 2'' at 15 GHz) is several times better than previously attained. At each frequency, the filament appears as a depression in the quiet Sun background. The depression is measurably wider and longer in extent than the corresponding H alpha filament at 1.45 GHz and 4.9 GHz, indicating that the depression is due in large part to a deficit in coronal density associated with the filament channel. In contrast, the shape of the radio depression at 15 CHz closely matches that of the H alpha filament. In addition, the 15 GHz map shows enhanced emission along both sides of the radio depression. A similar enhancement is seen in an observation of a second filament 4 days later, which suggests that the enhancement is a general feature of filaments. Possible causes of the enhanced emission are explored

  13. The evolution of compositionally and functionally distinct actin filaments.

    Science.gov (United States)

    Gunning, Peter W; Ghoshdastider, Umesh; Whitaker, Shane; Popp, David; Robinson, Robert C

    2015-06-01

    The actin filament is astonishingly well conserved across a diverse set of eukaryotic species. It has essentially remained unchanged in the billion years that separate yeast, Arabidopsis and man. In contrast, bacterial actin-like proteins have diverged to the extreme, and many of them are not readily identified from sequence-based homology searches. Here, we present phylogenetic analyses that point to an evolutionary drive to diversify actin filament composition across kingdoms. Bacteria use a one-filament-one-function system to create distinct filament systems within a single cell. In contrast, eukaryotic actin is a universal force provider in a wide range of processes. In plants, there has been an expansion of the number of closely related actin genes, whereas in fungi and metazoa diversification in tropomyosins has increased the compositional variety in actin filament systems. Both mechanisms dictate the subset of actin-binding proteins that interact with each filament type, leading to specialization in function. In this Hypothesis, we thus propose that different mechanisms were selected in bacteria, plants and metazoa, which achieved actin filament compositional variation leading to the expansion of their functional diversity. © 2015. Published by The Company of Biologists Ltd.

  14. Large-scale filaments associated with Milky Way spiral arms

    Science.gov (United States)

    Wang, Ke; Testi, Leonardo; Ginsburg, Adam; Walmsley, C. Malcolm; Molinari, Sergio; Schisano, Eugenio

    2015-07-01

    The ubiquity of filamentary structure at various scales throughout the Galaxy has triggered a renewed interest in their formation, evolution, and role in star formation. The largest filaments can reach up to Galactic scale as part of the spiral arm structure. However, such large-scale filaments are hard to identify systematically due to limitations in identifying methodology (i.e. as extinction features). We present a new approach to directly search for the largest, coldest, and densest filaments in the Galaxy, making use of sensitive Herschel Hi-GAL (Herschel Infrared Galactic Plane Survey) data complemented by spectral line cubes. We present a sample of the nine most prominent Herschel filaments, including six identified from a pilot search field plus three from outside the field. These filaments measure 37-99 pc long and 0.6-3.0 pc wide with masses (0.5-8.3) × 104 M⊙, and beam-averaged (28 arcsec, or 0.4-0.7 pc) peak H2 column densities of (1.7-9.3)× 1022 cm- 2. The bulk of the filaments are relatively cold (17-21 K), while some local clumps have a dust temperature up to 25-47 K. All the filaments are located within ≲60 pc from the Galactic mid-plane. Comparing the filaments to a recent spiral arm model incorporating the latest parallax measurements, we find that 7/9 of them reside within arms, but most are close to arm edges. These filaments are comparable in length to the Galactic scaleheight and therefore are not simply part of a grander turbulent cascade.

  15. Post-filament self-trapping of ultrashort laser pulses.

    Science.gov (United States)

    Mitrofanov, A V; Voronin, A A; Sidorov-Biryukov, D A; Andriukaitis, G; Flöry, T; Pugžlys, A; Fedotov, A B; Mikhailova, J M; Panchenko, V Ya; Baltuška, A; Zheltikov, A M

    2014-08-15

    Laser filamentation is understood to be self-channeling of intense ultrashort laser pulses achieved when the self-focusing because of the Kerr nonlinearity is balanced by ionization-induced defocusing. Here, we show that, right behind the ionized region of a laser filament, ultrashort laser pulses can couple into a much longer light channel, where a stable self-guiding spatial mode is sustained by the saturable self-focusing nonlinearity. In the limiting regime of negligibly low ionization, this post-filamentation beam dynamics converges to a large-scale beam self-trapping scenario known since the pioneering work on saturable self-focusing nonlinearities.

  16. Failure and nonfailure of fluid filaments in extension

    DEFF Research Database (Denmark)

    Hassager, Ole; Kolte, Mette Irene; Renardy, Michael

    1998-01-01

    The phenomenon of ductile failure of Newtonian and viscoelastic fluid filaments without surface tension is studied by a 2D finite element method and by ID non-linear analysis. The viscoelastic fluids are described by single integral constitutive equations. The main conclusions are: (1) Newtonian...... fluid filaments do not exhibit ductile failure without surface tension; (2) some viscoelastic fluids form stable filaments while other fluids exhibit ductile failure as a result of an elastic instability; (3) for large Deborah numbers, the Considere condition may be used to predict the Hencky strain...

  17. [Growth and metabolite production of the marine cyanobacterium Synechococcus sp. (Chroococcales) in function to irradiance].

    Science.gov (United States)

    Rosales-Loaiza, Néstor; Guevara, Miguel; Lodeiros, César; Morales, Ever

    2008-06-01

    Changes in salinity, temperature and irradiance during wet and dry seasons have induced metabolic versatility in cyanobacteria from saline environments. Cyanobacteria from these environments have biotechnological potential for the production of metabolites with pharmaceutical and industrial interest. We studied the growth, dry mass and metabolite production of the cyanobacterium Synechococcus sp. MOF-03 in function of irradiance (78, 156 and 234 micromol q m(-2) s(-1)). All batch cultures were maintained by triplicate in constant aeration, 12:12 h photoperiod, 30 +/- 2 degrees C and 35% per hundred. Maximum values of protein, carbohydrates and lipids, of 530.19 +/- 11.16, 408.94 +/- 4.27 and 56.20 +/- 1.17 microg ml(-1), respectively, were achieved at 78 micromol q m(-2) s(-1). Pigments, analyzed by HPLC, showed maximum values at 78 micromol q m(-2) s(-1) for chlorophyll a with 7.72 +/- 0.16 microg ml(-1), and at 234 micromol q m(-2) s(-1) for beta-carotene and zeaxanthin with 0.70 +/- 0.01 and 0.67 +/- 0.05 microg ml(-1). Chlorophyll a:beta-carotene ratio decreased from 17.15 to 6.91 at 78 and 234 micromol q m(-2) s(-'1); whereas beta-carotene:zeaxanthin ratio showed no changes between 78 and 156 micromol q m(-2) s(-1), around 1.21, and decreased at 234 micromol q m(-2) s(-1), to 1.04. Also, this cyanobacterium produced the greatest cell density and dry mass at 156 micromol q m(-2) s(-1), with 406.13 +/- 21.74 x l0(6) cell ml(-1) and 1.49 +/- 0.11 mg ml(-1), respectively. Exopolysaccharide production was stable between 156 y 234 micromol q m(-2) s(-1), around 110 microg ml(-1). This Synechococcus strain shows a great potential for the production of enriched biomass with high commercial value metabolites.

  18. Pyrene degradation by yeasts and filamentous fungi.

    Science.gov (United States)

    Romero, M Cristina; Salvioli, Mónica L; Cazau, M Cecilia; Arambarri, A M

    2002-01-01

    The saprotrophic soil fungi Fusarium solani (Mart.) Sacc., Cylindrocarpon didymum (Hartig) Wollenw, Penicillium variabile Sopp. and the yeasts Rhodotorula glutinis (Fresenius) Harrison and Rhodotorula minuta (Saito) Harrison were cultured in mineral medium with pyrene. The remaining pyrene concentrations were periodically determined during 20 incubation days, using HPLC. To assess the metabolism of pyrene degradation we added 0.1 microCi of [4,5,9,10] 14C-pyrene to each fungi culture and measured the radioactivity in the volatile organic substances, extractable, aqueous phase, biomass and 14CO2 fractions. The assays demonstrated that F. solani and R. glutinis metabolized pyrene as a sole source of carbon. Differences in their activities at the beginning of the cultures disappeared by the end of the experiment, when 32 and 37% of the original pyrene concentration was detected, for the soil fungi and yeasts, respectively. Among the filamentous fungi, F. solani was highly active and oxidized pyrene; moreover, small but significant degradation rates were observed in C. didymum and P. variahile cultures. An increase in the 14CO2 evolution was observed at the 17th day with cosubstrate. R. glutinis and R. minuta cultures showed similar ability to biotransform pyrene, and that 35% of the initial concentration was consumed at the end of the assay. The same results were obtained in the experiments with or without glucose as cosubstrate.

  19. Polymer dynamics driven by a helical filament

    Science.gov (United States)

    Balin, Andrew; Shendruk, Tyler; Zoettl, Andreas; Yeomans, Julia

    Microbial flagellates typically inhabit complex suspensions of extracellular polymeric material which can impact the swimming speed of motile microbes, filter-feeding of sessile cells, and the generation of biofilms. There is currently a need to better understand how the fundamental dynamics of polymers near active cells or flagella impacts these various phenomena. We study the hydrodynamic and steric influence of a rotating helical filament on suspended polymers using Stokesian Dynamics simulations. Our results show that as a stationary rotating helix pumps fluid along its long axis, nearby polymers migrate radially inwards and are elongated in the process. We observe that the actuation of the helix tends to increase the probability of finding polymeric material within its pervaded volume. At larger Weissenberg numbers, this accumulation of polymers within the vicinity of the helix is greater. Further, we have analysed the stochastic work performed by the helix on the polymers and we show that this quantity is positive on average and increases with polymer contour length. Our results provide a basis for understanding the microscopic interactions that govern cell dynamics in complex media. This work was supported through funding from the ERC Advanced Grant 291234 MiCE and we acknowledge EMBO funding to TNS (ALTF181-2013).

  20. Interfering with the wake of cylinder by flexible filaments

    Science.gov (United States)

    Pinelli, Alfredo; Omidyeganeh, Mohammad

    2015-11-01

    This work is the very first attempt to understand and optimize the configuration of flexible filaments placed on the lee side of a bluff body to manipulate flow transitions and bifurcations. It is found that the presence of a sparse set of flexible filaments on the lee side of a cylinder can interfere with the 2D-3D transition process resulting in elongation of recirculation bubble, inhibition of higher order unstable modes, and narrowing the global energy content about a particular shedding frequency. Filaments become effective when spacing between them is smaller than the dominant unstable mode at each particular Reynolds number, i.e. A and B modes. In another study, by a particular arrangement the reconfigured filaments can reduce pressure fluctuations in the wake and drop lift flluctuations significantly (~= 80 %).

  1. Positrusion Filament Recycling System for ISS, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The Positrusion ISS Recycler enables recycling of scrap and waste plastics into high-quality filament for 3D printers to enable sustainable in-situ manufacturing on...

  2. Effect of carbon and nitrogen assimilation on chlorophyll fluorescence emission by the cyanobacterium Anacystis nidulans

    Energy Technology Data Exchange (ETDEWEB)

    Romero, J.M.; Lara, C. (Instituto de Bioquimica Vegetal y Fotosintesis, Univ. de Sevilla y CSIC, Sevilla (ES)); Sivak, M.N. (Dept. of Biochemistry, Michigan State Univ., East Lansing (US))

    1992-01-01

    O{sub 2} evolution and chlorophyll A fluorescence emission have been monitored in intact cells of the cyanobacterium Anacystis nidulans 1402-1 to study the influence of carbon and nitrogen assimilation on the operation of the photosynthetic apparatus. The pattern of fluorescence induction in dark-adapted cyanobacterial cells was different from that of higher plants. Cyanobacteria undergo large, rapid state transitions upon illumination, which lead to marked changes in the fluorescence yield, complicating the estimation of quenching coefficients. The Kautsky effect was not evident, although it could be masked by a state II-state I transition, upon illumination with actinic light. The use of inhibitors of carbon assimilation such as D,L-glyceraldehyde or iodoacetamide allowed us to relate changes in variable fluorescence to active CO{sub 2} fixation. Ammonium, but not nitrate, induced non-photochemical fluorescence quenching, in agreement with a previous report on green algae, indicative of an ammonium-induced state i transition. (au).

  3. CRISPR/Cas9 mediated targeted mutagenesis of the fast growing cyanobacterium Synechococcus elongatus UTEX 2973.

    Science.gov (United States)

    Wendt, Kristen E; Ungerer, Justin; Cobb, Ryan E; Zhao, Huimin; Pakrasi, Himadri B

    2016-06-23

    As autotrophic prokaryotes, cyanobacteria are ideal chassis organisms for sustainable production of various useful compounds. The newly characterized cyanobacterium Synechococcus elongatus UTEX 2973 is a promising candidate for serving as a microbial cell factory because of its unusually rapid growth rate. Here, we seek to develop a genetic toolkit that enables extensive genomic engineering of Synechococcus 2973 by implementing a CRISPR/Cas9 editing system. We targeted the nblA gene because of its important role in biological response to nitrogen deprivation conditions. First, we determined that the Streptococcus pyogenes Cas9 enzyme is toxic in cyanobacteria, and conjugational transfer of stable, replicating constructs containing the cas9 gene resulted in lethality. However, after switching to a vector that permitted transient expression of the cas9 gene, we achieved markerless editing in 100 % of cyanobacterial exconjugants after the first patch. Moreover, we could readily cure the organisms of antibiotic resistance, resulting in a markerless deletion strain. High expression levels of the Cas9 protein in Synechococcus 2973 appear to be toxic and result in cell death. However, introduction of a CRISPR/Cas9 genome editing system on a plasmid backbone that leads to transient cas9 expression allowed for efficient markerless genome editing in a wild type genetic background.

  4. Anoxygenic Photosynthesis Controls Oxygenic Photosynthesis in a Cyanobacterium from a Sulfidic Spring

    KAUST Repository

    Klatt, Judith M.

    2015-03-15

    Before the Earth\\'s complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism\\'s affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 - during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life.

  5. Genetic analysis of amino acid transport in the facultatively heterotrophic cyanobacterium Synechocystis sp. Strain 6803

    International Nuclear Information System (INIS)

    Labarre, J.; Thuriaux, P.; Chauvat, F.

    1987-01-01

    The existence of active transport systems (permeases) operating on amino acids in the photoautotrophic cyanobacterium Synechocystis sp. strain 6803 was demonstrated by following the initial rates of uptake with 14 C-labeled amino acids, measuring the intracellular pools of amino acids, and isolating mutants resistant to toxic amino acids. One class of mutants (Pfa1) corresponds to a regulatory defect in the biosynthesis of the aromatic amino acids, but two other classes (Can1 and Aza1) are defective in amino acid transport. The Can1 mutants are defective in the active transport of three basic amino acids (arginine, histidine, and lysine) and in one of two transport systems operating on glutamine. The Aza1 mutants are not affected in the transport of the basic amino acids but have lost the capacity to transport all other amino acids except glutamate. The latter amino acid is probably transported by a third permease which could be identical to the Can1-independent transport operating on glutamine. Thus, genetic evidence suggests that strain 6803 has only a small number of amino acid transport systems with fairly broad specificity and that, with the exception of glutamine, each amino acid is accumulated by only one major transport system. Compared with heterotrophic bacteria such as Escherichia coli, these permeases are rather inefficient in terms of affinity (apparent K/sub m/ ranging from 6 to 60 μM) and of V/sub max/

  6. Advances in the Function and Regulation of Hydrogenase in the Cyanobacterium Synechocystis PCC6803

    Science.gov (United States)

    Cassier-Chauvat, Corinne; Veaudor, Théo; Chauvat, Franck

    2014-01-01

    In order to use cyanobacteria for the biological production of hydrogen, it is important to thoroughly study the function and the regulation of the hydrogen-production machine in order to better understand its role in the global cell metabolism and identify bottlenecks limiting H2 production. Most of the recent advances in our understanding of the bidirectional [Ni-Fe] hydrogenase (Hox) came from investigations performed in the widely-used model cyanobacterium Synechocystis PCC6803 where Hox is the sole enzyme capable of combining electrons with protons to produce H2 under specific conditions. Recent findings suggested that the Hox enzyme can receive electrons from not only NAD(P)H as usually shown, but also, or even preferentially, from ferredoxin. Furthermore, plasmid-encoded functions and glutathionylation (the formation of a mixed-disulfide between the cysteines residues of a protein and the cysteine residue of glutathione) are proposed as possible new players in the function and regulation of hydrogen production. PMID:25365180

  7. Anoxygenic photosynthesis controls oxygenic photosynthesis in a cyanobacterium from a sulfidic spring.

    Science.gov (United States)

    Klatt, Judith M; Al-Najjar, Mohammad A A; Yilmaz, Pelin; Lavik, Gaute; de Beer, Dirk; Polerecky, Lubos

    2015-03-01

    Before the Earth's complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism's affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 (-) during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life. Copyright © 2015, American Society for Microbiology. All Rights Reserved.

  8. A Novel Epiphytic Chlorophyll d-containing Cyanobacterium Isolated from a Mangrove-associated Red Alga.

    Science.gov (United States)

    Larkum, Anthony W D; Chen, Min; Li, Yaqiong; Schliep, Martin; Trampe, Erik; West, John; Salih, Anya; Kühl, Michael

    2012-12-01

    A new habitat and a new chlorophyll (Chl) d-containing cyanobacterium belonging to the genus Acaryochloris are reported in this study. Hyperspectral microscopy showed the presence of Chl d-containing microorganisms in epiphytic biofilms on a red alga (Gelidium caulacantheum) colonizing the pneumato-phores of a temperate mangrove (Avicennia marina). The presence of Chl d was further proven by high performance liquid chromatography (HPLC)-based pigment analysis and by confocal imaging of cultured cells. Enrichment of mangrove biofilm samples under near-infrared radiation (NIR) yielded the new Acaryochloris sp. MPGRS1, which was closely related in terms of 16S rRNA gene sequence to an isolate from the hypertrophic Salton Sea, USA. The new isolate used Chl d as its major photopigment; Chl d and Chl a contents were ~98% and 1%-2% of total cellular chlorophyll, respectively. These findings expand the variety of ecological niches known to harbor Chl d-containing cyanobacteria and support our working hypothesis that such oxyphototrophs may be ubiquitous in habitats depleted of visible light, but with sufficient NIR exposure. © 2012 Phycological Society of America.

  9. Anti-MRSA-acting carbamidocyclophanes H-L from the Vietnamese cyanobacterium Nostoc sp. CAVN2.

    Science.gov (United States)

    Preisitsch, Michael; Harmrolfs, Kirsten; Pham, Hang T L; Heiden, Stefan E; Füssel, Anna; Wiesner, Christoph; Pretsch, Alexander; Swiatecka-Hagenbruch, Monika; Niedermeyer, Timo H J; Müller, Rolf; Mundt, Sabine

    2015-03-01

    The methanol extract of the Vietnamese freshwater cyanobacterium Nostoc sp. CAVN2 exhibited cytotoxic effects against MCF-7 and 5637 cancer cell lines as well as against nontumorigenic FL and HaCaT cells and was active against methicillin-resistant Staphylococcus aureus (MRSA) and Streptococcus pneumoniae. High-resolution mass spectrometric analysis indicated the presence of over 60 putative cyclophane-like compounds in an antimicrobially active methanol extract fraction. A paracyclophanes-focusing extraction and separation methodology led to the isolation of 5 new carbamidocyclophanes (1-5) and 11 known paracyclophanes (6-16). The structures and their stereochemical configurations were elucidated by a combination of spectrometric and spectroscopic methods including HRMS, 1D and 2D NMR analyses and detailed comparative CD analysis. The newly described monocarbamoylated [7.7]paracyclophanes (1, 2, 4 and 5) differ by a varying degree of chlorination in the side chains. Carbamidocyclophane J (3) is the very first reported carbamidocyclophane bearing a single halogenation in both butyl residues. Based on previous studies a detailed phylogenetic examination of cyclophane-producing cyanobacteria was carried out. The biological evaluation of 1-16 against various clinical pathogens highlighted a remarkable antimicrobial activity against MRSA with MICs of 0.1-1.0 μM, and indicated that the level of antibacterial activity is related to the presence of carbamoyl moieties.

  10. Metabolomic approach to optimizing and evaluating antibiotic treatment in the axenic culture of cyanobacterium Nostoc flagelliforme.

    Science.gov (United States)

    Han, Pei-pei; Jia, Shi-ru; Sun, Ying; Tan, Zhi-lei; Zhong, Cheng; Dai, Yu-jie; Tan, Ning; Shen, Shi-gang

    2014-09-01

    The application of antibiotic treatment with assistance of metabolomic approach in axenic isolation of cyanobacterium Nostoc flagelliforme was investigated. Seven antibiotics were tested at 1-100 mg L(-1), and order of tolerance of N. flagelliforme cells was obtained as kanamycin > ampicillin, tetracycline > chloromycetin, gentamicin > spectinomycin > streptomycin. Four antibiotics were selected based on differences in antibiotic sensitivity of N. flagelliforme and associated bacteria, and their effects on N. flagelliforme cells including the changes of metabolic activity with antibiotics and the metabolic recovery after removal were assessed by a metabolomic approach based on gas chromatography-mass spectrometry combined with multivariate analysis. The results showed that antibiotic treatment had affected cell metabolism as antibiotics treated cells were metabolically distinct from control cells, but the metabolic activity would be recovered via eliminating antibiotics and the sequence of metabolic recovery time needed was spectinomycin, gentamicin > ampicillin > kanamycin. The procedures of antibiotic treatment have been accordingly optimized as a consecutive treatment starting with spectinomycin, then gentamicin, ampicillin and lastly kanamycin, and proved to be highly effective in eliminating the bacteria as examined by agar plating method and light microscope examination. Our work presented a strategy to obtain axenic culture of N. flagelliforme and provided a method for evaluating and optimizing cyanobacteria purification process through diagnosing target species cellular state.

  11. Simultaneous Production of Anabaenopeptins and Namalides by the Cyanobacterium Nostoc sp. CENA543.

    Science.gov (United States)

    Shishido, Tânia K; Jokela, Jouni; Fewer, David P; Wahlsten, Matti; Fiore, Marli F; Sivonen, Kaarina

    2017-11-17

    Anabaenopeptins are a diverse group of cyclic peptides, which contain an unusual ureido linkage. Namalides are shorter structural homologues of anabaenopeptins, which also contain an ureido linkage. The biosynthetic origins of namalides are unknown despite a strong resemblance to anabaenopeptins. Here, we show the cyanobacterium Nostoc sp. CENA543 strain producing new (nostamide B-E (2, 4, 5, and 6)) and known variants of anabaenopeptins (schizopeptin 791 (1) and anabaenopeptin 807 (3)). Surprisingly, Nostoc sp. CENA543 also produced namalide B (8) and the new namalides D (7), E (9), and F (10) in similar amounts to anabaenopeptins. Analysis of the complete Nostoc sp. CENA543 genome sequence indicates that both anabaenopeptins and namalides are produced by the same biosynthetic pathway through module skipping during biosynthesis. This unique process involves the skipping of two modules present in different nonribosomal peptide synthetases during the namalide biosynthesis. This skipping is an efficient mechanism since both anabaenopeptins and namalides are synthesized in similar amounts by Nostoc sp. CENA543. Consequently, gene skipping may be used to increase and possibly broaden the chemical diversity of related peptides produced by a single biosynthetic gene cluster. Genome mining demonstrated that the anabaenopeptin gene clusters are widespread in cyanobacteria and can also be found in tectomicrobia bacteria.

  12. Merocyclophanes C and D from the Cultured Freshwater Cyanobacterium Nostoc sp. (UIC 10110).

    Science.gov (United States)

    May, Daniel S; Chen, Wei-Lun; Lantvit, Daniel D; Zhang, Xiaoli; Krunic, Aleksej; Burdette, Joanna E; Eustaquio, Alessandra; Orjala, Jimmy

    2017-04-28

    Merocyclophanes C and D (1 and 2) were isolated from the cell extract of the cultured cyanobacterium UIC 10110. The structures were determined by one-dimensional nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry and confirmed by 2D NMR techniques. The absolute configurations were determined using electronic circular dichroism spectroscopy. Merocyclophanes C and D represent the first known analogues of the merocyclophane core structure, a recently discovered scaffold of [7,7] paracyclophanes characterized by an α-branched methyl at C-1/C-14; 1 and 2 showed antiproliferative activity against the MDA-MB-435 cell line with IC 50 values of 1.6 and 0.9 μM, respectively. Partial 16S analysis determined UIC 10110 to be a Nostoc sp., and it was found to clade with UIC 10062 Nostoc sp., the only other strain known to produce merocyclophanes. The genome of UIC 10110 was sequenced, and a biosynthetic gene cluster was identified that is proposed to encode type I and type III polyketide synthases that are potentially responsible for production of the merocyclophanes; however, further experiments will be required to verify the true function of the gene cluster. The gene cluster provides a genetic basis for the observed structural differences of the [7,7] paracyclophane core structures.

  13. Structural elucidation and molecular docking of a novel antibiotic compound from cyanobacterium Nostoc sp. MGL001

    Directory of Open Access Journals (Sweden)

    Niveshika No Name

    2016-11-01

    Full Text Available Cyanobacteria are rich source of array of bioactive compounds. The present study reports a novel antibacterial bioactive compound purified from cyanobacterium Nostoc sp. MGL001 using various chromatographic techniques viz. thin layer chromatography (TLC and high performance liquid chromatography (HPLC. Further characterization was done using electrospray ionisation mass spectroscopy (ESIMS and nuclear magnetic resonance (NMR and predicted structure of bioactive compound was 9-Ethyliminomethyl-12-(morpholin - 4 - ylmethoxy -5, 8, 13, 16 – tetraaza – hexacene - 2, 3 dicarboxylic acid (EMTAHDCA. Structure of EMTAHDCA clearly indicated that it is a novel compound that was not reported in literature or natural product database. The compound exhibited growth inhibiting effects mainly against the gram negative bacterial strains and produced maximum zone of inhibition at 150 μg/mL concentration. The compound was evaluated through in silico studies for its ability to bind 30S ribosomal fragment (PDB ID: 1YRJ, 1MWL, 1J7T and 1LC4 and OmpF porin protein (4GCP, 4GCQ and 4GCS which are the common targets of various antibiotic drugs. Comparative molecular docking study revealed that EMTAHDCA has strong binding affinity for these selected targets in comparison to a number of most commonly used antibiotics. The ability of EMTAHDCA to bind the active sites on the proteins and 30S ribosomal fragments where the antibiotic drugs generally bind indicated that it is functionally similar to the commercially available drugs.

  14. Semicontinuous cultivation of the Cyanobacterium Spirulina platensis in a closed photobioreactor

    Energy Technology Data Exchange (ETDEWEB)

    Reichert, C.C.; Costa, J.A.V. [Fundacao Universidade Federal do Rio Grande (FURG), Rio Grande, RS (Brazil). Dept. de Quimica], Email: dqmjorge@furg.br; Reinehr, C.O. [Universidade de Passo Fundo, RS (Brazil). Centro de Pesquisa em Alimentacao], Email: reinehr@upf.br

    2006-01-15

    The cultivation of photosynthetic microorganisms such as the cyanobacterium Spirulina platensis has been studied by researchers in many countries because these organisms can produce products with industrial potential. We studied the specific growth rate ({mu}{sub x}, day{sup -1}) and productivity (P{sub x}, in mg/L/day of Spirulina platensis biomass, dry weight basis) of two S. platensis strains (LEB-52 and Paracas) growing in aerated semicontinuous culture in two-liter Erlenmeyer flasks for 90 days (2160 h) at 30 deg C under 2500 lux of illumination in a 12 h photoperiod. Independent of the S. platensis strain used we found that low biomass concentrations (0.50 g/L) and high renewal rates (50% v/v) resulted in a high specific growth rate ({mu}{sub x} = 0.111 day{sup -1}) and high productivity (P{sub x} = 42.3 mg/L/day). These values are two to four times higher than those obtained in simple batch cultivation and indicate that the semicontinuous cultivation of S. platensis is viable. (author)

  15. Semicontinuous cultivation of the cyanobacterium Spirulina platensis in a closed photobioreactor

    Directory of Open Access Journals (Sweden)

    C. C. Reichert

    2006-03-01

    Full Text Available The cultivation of photosynthetic microorganisms such as the cyanobacterium Spirulina platensis has been studied by researchers in many countries because these organisms can produce products with industrial potential. We studied the specific growth rate (µx, day-1 and productivity (Px, in mg/L/day of Spirulina platensis biomass, dry weight basis of two S. platensis strains (LEB-52 and Paracas growing in aerated semicontinuous culture in two-liter Erlenmeyer flasks for 90 days (2160 h at 30°C under 2500 lux of illumination in a 12 h photoperiod. Independent of the S. platensis strain used we found that low biomass concentrations (0.50 g/L and high renewal rates (50% v/v resulted in a high specific growth rate (µx = 0.111 day-1 and high productivity (Px = 42.3 mg/L/day. These values are two to four times higher than those obtained in simple batch cultivation and indicate that the semicontinuous cultivation of S. platensis is viable.

  16. Anoxygenic Photosynthesis Controls Oxygenic Photosynthesis in a Cyanobacterium from a Sulfidic Spring

    KAUST Repository

    Klatt, Judith M.; Alnajjar, Mohammad Ahmad; Yilmaz, Pelin; Lavik, Gaute; de Beer, Dirk; Polerecky, Lubos

    2015-01-01

    Before the Earth's complete oxygenation (0.58 to 0.55 billion years [Ga] ago), the photic zone of the Proterozoic oceans was probably redox stratified, with a slightly aerobic, nutrient-limited upper layer above a light-limited layer that tended toward euxinia. In such oceans, cyanobacteria capable of both oxygenic and sulfide-driven anoxygenic photosynthesis played a fundamental role in the global carbon, oxygen, and sulfur cycle. We have isolated a cyanobacterium, Pseudanabaena strain FS39, in which this versatility is still conserved, and we show that the transition between the two photosynthetic modes follows a surprisingly simple kinetic regulation controlled by this organism's affinity for H2S. Specifically, oxygenic photosynthesis is performed in addition to anoxygenic photosynthesis only when H2S becomes limiting and its concentration decreases below a threshold that increases predictably with the available ambient light. The carbon-based growth rates during oxygenic and anoxygenic photosynthesis were similar. However, Pseudanabaena FS39 additionally assimilated NO3 - during anoxygenic photosynthesis. Thus, the transition between anoxygenic and oxygenic photosynthesis was accompanied by a shift of the C/N ratio of the total bulk biomass. These mechanisms offer new insights into the way in which, despite nutrient limitation in the oxic photic zone in the mid-Proterozoic oceans, versatile cyanobacteria might have promoted oxygenic photosynthesis and total primary productivity, a key step that enabled the complete oxygenation of our planet and the subsequent diversification of life.

  17. Proteomic analysis of the cyanobacterium of the Azolla symbiosis: identity, adaptation, and NifH modification.

    Science.gov (United States)

    Ekman, Martin; Tollbäck, Petter; Bergman, Birgitta

    2008-01-01

    Cyanobacteria are able to form stable nitrogen-fixing symbioses with diverse eukaryotes. To extend our understanding of adaptations imposed by plant hosts, two-dimensional gel electrophoresis and mass spectrometry (MS) were used for comparative protein expression profiling of a cyanobacterium (cyanobiont) dwelling in leaf cavities of the water-fern Azolla filiculoides. Homology-based protein identification using peptide mass fingerprinting [matrix-assisted laser desorption ionization-time of flight (MALDI-TOF-MS)], tandem MS analyses, and sequence homology searches resulted in an identification success rate of 79% of proteins analysed in the unsequenced cyanobiont. Compared with a free-living strain, processes related to energy production, nitrogen and carbon metabolism, and stress-related functions were up-regulated in the cyanobiont while photosynthesis and metabolic turnover rates were down-regulated, stressing a slow heterotrophic mode of growth, as well as high heterocyst frequencies and nitrogen-fixing capacities. The first molecular data set on the nature of the NifH post-translational modification in cyanobacteria was also obtained: peptide mass spectra of the protein demonstrated the presence of a 300-400 Da protein modification localized to a specific 13 amino acid sequence, within the part of the protein that is ADP-ribosylated in other bacteria and close to the active site of nitrogenase. Furthermore, the distribution of the highest scoring database hits for the identified proteins points to the possibility of using proteomic data in taxonomy.

  18. Crystal Structure of Allophycocyanin from Marine Cyanobacterium Phormidium sp. A09DM.

    Directory of Open Access Journals (Sweden)

    Ravi Raghav Sonani

    Full Text Available Isolated phycobilisome (PBS sub-assemblies have been widely subjected to X-ray crystallography analysis to obtain greater insights into the structure-function relationship of this light harvesting complex. Allophycocyanin (APC is the phycobiliprotein always found in the PBS core complex. Phycocyanobilin (PCB chromophores, covalently bound to conserved Cys residues of α- and β- subunits of APC, are responsible for solar energy absorption from phycocyanin and for transfer to photosynthetic apparatus. In the known APC structures, heterodimers of α- and β- subunits (known as αβ monomers assemble as trimer or hexamer. We here for the first time report the crystal structure of APC isolated from a marine cyanobacterium (Phormidium sp. A09DM. The crystal structure has been refined against all the observed data to the resolution of 2.51 Å to Rwork (Rfree of 0.158 (0.229 with good stereochemistry of the atomic model. The Phormidium protein exists as a trimer of αβ monomers in solution and in crystal lattice. The overall tertiary structures of α- and β- subunits, and trimeric quaternary fold of the Phormidium protein resemble the other known APC structures. Also, configuration and conformation of the two covalently bound PCB chromophores in the marine APC are same as those observed in fresh water cyanobacteria and marine red algae. More hydrophobic residues, however, constitute the environment of the chromophore bound to α-subunit of the Phormidium protein, owing mainly to amino acid substitutions in the marine protein.

  19. Detection of weed algae in open pond cultures of Cyanobacterium aponinum using PAM

    Directory of Open Access Journals (Sweden)

    Dominik Winckelmann

    2016-02-01

    Full Text Available Abstract The potential use of non-arable land in the al-Wusta region of the Sultanate of Oman for the production of algae biomass was examined. Brackish cleaned production water from oil production supplemented with commercial fertilizer was used as growth medium. The indigenous isolate Cyanobacterium aponinum WP7(1 was grown in open ponds using batch or semi-continuous cultivation. Biomass production rates of 15–24 g/m2/day were achieved. The change of salinity due to evaporation, which was thought to be a major challenge, did not exceed 35 ppt. All cultures showed contaminations with weed algae. Contaminations with green algae or diatoms were detectable using fluorescence pattern excited by four different wavelengths using a pulse-amplitude-modulation chlorophyll fluorometer (PAM. It is possible to estimate the health level and the mayor groups of which a culture is composed using the PAM method. Therefore, the fluorescence of the photosynthetically inactive sample is compared with the fluorescence after all copies of photosystem II were closed by exposing the sample to a high-intensity light beam. A detection limit of one weed algae cell in a hundred cells was achieved.

  20. Anilofos tolerance and its mineralization by the cyanobacterium Synechocystis sp. strain PUPCCC 64.

    Directory of Open Access Journals (Sweden)

    D P Singh

    Full Text Available This study deals with anilofos tolerance and its mineralization by the common rice field cyanobacterium Synechocystis sp. strain PUPCCC 64. The organism tolerated anilofos up to 25 mg L(-1. The herbicide caused inhibitory effects on photosynthetic pigments of the test organism in a dose-dependent manner. The organism exhibited 60, 89, 96, 85 and 79% decrease in chlorophyll a, carotenoids, phycocyanin, allophycocyanin and phycoerythrin, respectively, in 20 mg L(-1 anilofos on day six. Activities of superoxide dismutase, catalase and peroxidase increased by 1.04 to 1.80 times over control cultures in presence of 20 mg L(-1 anilofos. Glutathione content decreased by 26% while proline content was unaffected by 20 mg L(-1 anilofos. The test organism showed intracellular uptake and metabolized the herbicide. Uptake of herbicide by test organism was fast during initial six hours followed by slow uptake until 120 hours. The organism exhibited maximum anilofos removal at 100 mg protein L(-1, pH 8.0 and 30°C. Its growth in phosphate deficient basal medium in the presence of anilofos (2.5 mg L(-1 indicated that herbicide was used by the strain PUPCCC 64 as a source of phosphate.

  1. CyanOmics: an integrated database of omics for the model cyanobacterium Synechococcus sp. PCC 7002.

    Science.gov (United States)

    Yang, Yaohua; Feng, Jie; Li, Tao; Ge, Feng; Zhao, Jindong

    2015-01-01

    Cyanobacteria are an important group of organisms that carry out oxygenic photosynthesis and play vital roles in both the carbon and nitrogen cycles of the Earth. The annotated genome of Synechococcus sp. PCC 7002, as an ideal model cyanobacterium, is available. A series of transcriptomic and proteomic studies of Synechococcus sp. PCC 7002 cells grown under different conditions have been reported. However, no database of such integrated omics studies has been constructed. Here we present CyanOmics, a database based on the results of Synechococcus sp. PCC 7002 omics studies. CyanOmics comprises one genomic dataset, 29 transcriptomic datasets and one proteomic dataset and should prove useful for systematic and comprehensive analysis of all those data. Powerful browsing and searching tools are integrated to help users directly access information of interest with enhanced visualization of the analytical results. Furthermore, Blast is included for sequence-based similarity searching and Cluster 3.0, as well as the R hclust function is provided for cluster analyses, to increase CyanOmics's usefulness. To the best of our knowledge, it is the first integrated omics analysis database for cyanobacteria. This database should further understanding of the transcriptional patterns, and proteomic profiling of Synechococcus sp. PCC 7002 and other cyanobacteria. Additionally, the entire database framework is applicable to any sequenced prokaryotic genome and could be applied to other integrated omics analysis projects. Database URL: http://lag.ihb.ac.cn/cyanomics. © The Author(s) 2015. Published by Oxford University Press.

  2. Effect of Selected Plant Extracts and D- and L-Lysine on the Cyanobacterium Microcystis aeruginosa

    Directory of Open Access Journals (Sweden)

    Miquel Lürling

    2014-06-01

    Full Text Available We tested extracts from Fructus mume, Salvia miltiorrhiza and Moringa oleifera as well as L-lysine and D-Lysine as curative measures to rapidly suppress the cyanobacterium Microcystis aeruginosa NIVA-CYA 43. We tested these compounds under similar conditions to facilitate comparisons. We hypothesized that for each compound, relatively low concentrations—i.e., 5–50 mg L−1, would reduce M. aeruginosa biomass. At these low concentrations, only L-lysine caused a decline in M. aeruginosa biomass at ≥4.3 mg L−1. F. mume extract was effective to do so at high concentrations, i.e., at ≥240 mg L−1, but the others were virtually non-effective. Low pH caused by organic acids is a probable explanation for the effect of F. mume extract. No complete wipe-outs of the experimental population were achieved as Photosystem II efficiency showed a recovery after six days. L-lysine may be effective at low concentrations—meaning low material costs. However, the effect of L-lysine seems relatively short-lived. Overall, the results of our study did not support the use of the tested plant extracts and amino-acid as promising candidates for curative application in M. aeruginosa bloom control.

  3. Theoretical investigation of biomass productivities achievable in solar rectangular photobioreactors for the cyanobacterium Arthrospira platensis.

    Science.gov (United States)

    Pruvost, Jeremy; Cornet, J F; Goetz, Vincent; Legrand, Jack

    2012-01-01

    Modeling was done to simulate whole-year running of solar rectangular photobioreactors (PBRs). Introducing the concept of ideal reactor, the maximal biomass productivity that could be achieved on Earth on nitrate as N-source was calculated. Two additional factors were also analyzed with respect to dynamic calculations over the whole year: the effect of PBR location and the effects of given operating conditions on the resulting decrease in productivity compared with the ideal one. Simulations were conducted for the cyanobacterium Arthospira platensis, giving an ideal productivity (upper limit) in the range 55-60 tX ha(-1) year(-1) for a sun tracking system (and around 35-40 tX ha(-1) year(-1) for a fixed horizontal PBR). For an implantation in France (Nantes, west coast), the modification in irradiation conditions resulted in a decrease in biomass productivity of 40%. Various parameters were investigated, with special emphasis on the influence of the incident angle of solar illumination on resulting productivities, affecting both light capture and light transfer inside the bulk culture. It was also found that with appropriate optimization of the residence time as permitted by the model, productivities close to maximal could be achieved for a given location. Copyright © 2012 American Institute of Chemical Engineers (AIChE).

  4. Acclimation to and recovery from cadmium and zinc exposure by a freshwater cyanobacterium, Microcystis aeruginosa

    International Nuclear Information System (INIS)

    Zeng Jin; Yang Liuyan; Wang Wenxiong

    2009-01-01

    To understand the metal tolerance of a bloom-forming cyanobacterium, Microcystis aeruginosa, we investigated its acclimation to and recovery from cadmium (Cd) and zinc (Zn) exposure. The intracellular Cd and Zn (intra-Cd and intra-Zn) quotas increased upon acclimation to increased metal concentrations and were reduced following 1-day or 5-day recovery. Different acclimation to varying metal concentrations or durations (5 days or 15 days) did not have significant effects on the short-term uptake of Cd or Zn, whereas a 1-day recovery period promoted Cd or Zn uptake significantly. The values of median growth-inhibition concentrations (free ion concentration or intracellular quota) increased when the cyanobacterial cells were acclimated to higher Cd or Zn concentrations, indicating that M. aeruginosa became more tolerant to these metals. Consistent with the significant increase in metal uptake, the cyanobacteria become very sensitive to metals following 1-day recovery. A longer recovery (5 days) led to comparable uptake and toxicity responses to the controls. The efflux rate constants were not significantly different following metal acclimation. In the subcellular metal measurements, Cd was mostly distributed in the soluble fraction, whereas Zn was distributed evenly in the adsorbed, insoluble and soluble fractions of the cells. This study suggested the strong ability of these cyanobacteria to acclimate to different environments.

  5. Enhanced ferrihydrite dissolution by a unicellular, planktonic cyanobacterium: a biological contribution to particulate iron bioavailability.

    Science.gov (United States)

    Kranzler, Chana; Kessler, Nivi; Keren, Nir; Shaked, Yeala

    2016-12-01

    Iron (Fe) bioavailability, as determined by its sources, sinks, solubility and speciation, places severe environmental constraints on microorganisms in aquatic environments. Cyanobacteria are a widespread group of aquatic, photosynthetic microorganisms with especially high iron requirements. While iron exists predominantly in particulate form, little is known about its bioavailability to cyanobacteria. Some cyanobacteria secrete iron solubilizing ligands called siderophores, yet many environmentally relevant strains do not have this ability. This work explores the bioavailability of amorphous synthetic Fe-oxides (ferrihydrite) to the non-siderophore producing, unicellular cyanobacterium, Synechocystis sp PCC 6803. Iron uptake assays with 55 ferrihydrite established dissolution as a critical prerequisite for iron transport. Dissolution assays with the iron binding ligand, desferrioxamine B, demonstrated that Synechocystis 6803 enhances ferrihydrite dissolution, exerting siderophore-independent biological influence on ferrihydrite bioavailability. Dissolution mechanisms were studied using a range of experimental conditions; both cell-particle physical proximity and cellular electron flow were shown to be important determinants of bio-dissolution by Synechocystis 6803. Finally, the effects of ferrihydrite stability on bio-dissolution rates and cell physiology were measured, integrating biological and chemical aspects of ferrihydrite bioavailability. Collectively, these findings demonstrate that Synechocystis 6803 actively dissolves ferrihydrite, highlighting a significant biological component to mineral phase iron bioavailability in aquatic environments. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.

  6. A new antibiotic produced by the cyanobacterium-symbiotic fungus Simplicillium lanosoniveum.

    Science.gov (United States)

    Dong, Qinglin; Dong, Rongzhen; Xing, Xiangying; Li, Yukuan

    2018-06-01

    The culture broth of the cyanobacterium-symbiotic fungus Simplicillium lanosoniveum var. Tianjinienss Q. L. Dong exhibited unanticipated antibacterial activities against the Gram-positive bacteria, particularly the pathogenic bacterium Staphylococcus aureus, indicating the secretion of antibiotic-like metabolite, for which the modified Sabouraud medium was the suitable medium. The antibiotic-like metabolite was separated with macroporous resins CT-12 (absorption) and 95% ethanol (desorption), purified by ion-exchange resins D301T and displayed a characteristic absorption peak at 228 nm, suggesting the presence of nitrogen. The negative biuret and ninhydrin tests confirmed the absence of -NH 2 and -COOH groups. Further, HPLC and mass spectrometry analyses showed that the retention time and molecular weight of the antibiotic-like metabolite were 4.1031 min and 163.0182 (Δ ± 2.3 ppm), respectively. Taking together, we speculated that the antibiotic-like metabolite was a new antibiotic structurally similar to alkaloid, which was the first one isolated from the species of Simplicillium genus.

  7. Bioprocess Engineering Aspects of Biopolymer Production by the Cyanobacterium Spirulina Strain LEB 18

    Directory of Open Access Journals (Sweden)

    Roberta Guimarães Martins

    2014-01-01

    Full Text Available Microbial biopolymers can replace environmentally damaging plastics derived from petrochemicals. We investigated biopolymer synthesis by the cyanobacterium Spirulina strain LEB 18. Autotrophic culture used unmodified Zarrouk medium or modified Zarrouk medium in which the NaNO3 content was reduced to 0.25 g L−1 and the NaHCO3 content reduced to 8.4 g L−1 or increased to 25.2 g L−1. Heterotrophic culture used modified Zarrouk medium containing 0.25 g L−1 NaNO3 with the NaHCO3 replaced by 0.2 g L−1, 0.4 g L−1, or 0.6 g L−1 of glucose (C6H12O6 or sodium acetate (CH3COONa. Mixotrophic culture used modified Zarrouk medium containing 0.25 g L−1 NaNO3 plus 16.8 g L−1 NaHCO3 with the addition of 0.2 g L−1, 0.4 g L−1, or 0.6 g L−1 of glucose or sodium acetate. The highest biopolymer yield was 44% when LEB 18 was growing autotrophically in media containing 0.25 g L−1 NaNO3 and 8.4 g L−1 NaHCO3.

  8. Inhibitory effects of sanguinarine against the cyanobacterium Microcystis aeruginosa NIES-843 and possible mechanisms of action

    Energy Technology Data Exchange (ETDEWEB)

    Shao, Jihai [College of Resources and Environment, Hunan Agricultural University, Changsha 410128 (China); Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Agricultural University, Changsha 410128 (China); Liu, Deming [State Key Laboratory Breeding Base of Crop Germplasm Innovation and Resource Utilization, Hunan Agricultural University, Changsha 410128 (China); Gong, Daoxin; Zeng, Qingru; Yan, Zhiyong [College of Resources and Environment, Hunan Agricultural University, Changsha 410128 (China); Gu, Ji-Dong, E-mail: jdgu@hku.hk [Hunan Provincial Key Laboratory of Farmland Pollution Control and Agricultural Resources Use, Hunan Agricultural University, Changsha 410128 (China); Laboratory of Environmental Microbiology and Toxicology, School of Biological Sciences, The University of Hong Kong, Hong Kong SAR (China)

    2013-10-15

    Highlights: •Sanguinarine was found as a strong algicidal biologically derived substance. •Sanguinarine can induce oxidative stress in the cells of Microcystis aeruginosa. •Photosystem is a target of toxicity of sanguinarine on M. aeruginosa. •Sanguinarine can induce DNA damage and inhibit cell division. -- Abstract: Sanguinarine showed strong inhibitory effect against Microcystis aeruginosa, a typical water bloom-forming and microcystins-producing cyanobacterium. The EC50 of sanguinarine against the growth of M. aeruginosa NIES-843 was 34.54 ± 1.17 μg/L. Results of chlorophyll fluorescence transient analysis indicated that all the electron donating side, accepting side, and the reaction center of the Photosystem II (PS II) were the targets of sanguinarine against M. aeruginosa NIES-843. The elevation of reactive oxygen species (ROS) level in the cells of M. aeruginosa NIES-843 upon exposure indicated that sanguinarine induced oxidative stress in the active growing cells of M. aeruginosa NIES-843. Further results of gene expression analysis indicated that DNA damage and cell division inhibition were also involved in the inhibitory action mechanism of sanguinarine against M. aeruginosa NIES-843. The inhibitory characteristics of sanguinarine against M. aeruginosa suggest that the ecological- and public health-risks need to be evaluated before its application in cyanobacterial bloom control to avoid devastating events irreversibly.

  9. The architecture and fine structure of gill filaments in the brown ...

    African Journals Online (AJOL)

    Special attention was paid to filament architecture, ennervation of filaments, number and type of cells populating filament epithelia and variations in epithelial cell morphology and cilia ultrastructure. Filament shape was maintained by thickened chi-tln and strategically placed smooth myocytes. The epithelium was populated ...

  10. Heterocyst placement strategies to maximize the growth of cyanobacterial filaments

    International Nuclear Information System (INIS)

    Brown, Aidan I; Rutenberg, Andrew D

    2012-01-01

    Under conditions of limited fixed-nitrogen, some filamentous cyanobacteria develop a regular pattern of heterocyst cells that fix nitrogen for the remaining vegetative cells. We examine three different heterocyst placement strategies by quantitatively modelling filament growth while varying both external fixed-nitrogen and leakage from the filament. We find that there is an optimum heterocyst frequency which maximizes the growth rate of the filament; the optimum frequency decreases as the external fixed-nitrogen concentration increases but increases as the leakage increases. In the presence of leakage, filaments implementing a local heterocyst placement strategy grow significantly faster than filaments implementing random heterocyst placement strategies. With no extracellular fixed-nitrogen, consistent with recent experimental studies of Anabaena sp. PCC 7120, the modelled heterocyst spacing distribution using our local heterocyst placement strategy is qualitatively similar to experimentally observed patterns. As external fixed-nitrogen is increased, the spacing distribution for our local placement strategy retains the same shape, while the average spacing between heterocysts continuously increases. (paper)

  11. Radiation-induced grafting of acrylic acid onto polyethylene filaments

    International Nuclear Information System (INIS)

    Kaji, K.; Sakurada, I.; Okada, T.

    1981-01-01

    Radiation-induced grafting of acrylic acid onto high density polyethylene (PE) filaments was carried out in order to raise softening temperature and impart flame retardance and hydrophilic properties. Mutual γ-irradiation method was employed for the grafting in a mixture of acrylic acid (AA), ethylene dichloride and water containing a small amount of ferrous ammonium sulfate. The rate of grafting was very low at room temperature. On the other hand, large percent grafts were obtained when the grafting was performed at an elevated temperature. Activation energy for the initial rate of grafting was found to be 17 kcal/mol between 20 and 60 0 C and 10 kcal/ mol between 60 and 80 0 C. Original PE filament begins to shrink at 70 0 C, shows maximum shrinkage of 50% at 130 0 C and then breaks off at 136 0 C. When a 34% AA graft is converted to metallic salt the graft filament retains its filament form even above 300 0 C and gives maximum shrinkage of 15%. Burning tests by a wire-netting basket method indicate that graft filaments and their metallic salts do not form melting drops upon burning and are self-extinguishing. Original PE filament shows no moisture absorption; however, that of AA-grafted PE increases with increasing graft percent. (author)

  12. Optical spectroscopy using gas-phase femtosecond laser filamentation.

    Science.gov (United States)

    Odhner, Johanan; Levis, Robert

    2014-01-01

    Femtosecond laser filamentation occurs as a dynamic balance between the self-focusing and plasma defocusing of a laser pulse to produce ultrashort radiation as brief as a few optical cycles. This unique source has many properties that make it attractive as a nonlinear optical tool for spectroscopy, such as propagation at high intensities over extended distances, self-shortening, white-light generation, and the formation of an underdense plasma. The plasma channel that constitutes a single filament and whose position in space can be controlled by its input parameters can span meters-long distances, whereas multifilamentation of a laser beam can be sustained up to hundreds of meters in the atmosphere. In this review, we briefly summarize the current understanding and use of laser filaments for spectroscopic investigations of molecules. A theoretical framework of filamentation is presented, along with recent experimental evidence supporting the established understanding of filamentation. Investigations carried out on vibrational and rotational spectroscopy, filament-induced breakdown, fluorescence spectroscopy, and backward lasing are discussed.

  13. The Weak Lensing Masses of Filaments between Luminous Red Galaxies

    Science.gov (United States)

    Epps, Seth D.; Hudson, Michael J.

    2017-07-01

    In the standard model of non-linear structure formation, a cosmic web of dark-matter-dominated filaments connects dark matter haloes. In this paper, we stack the weak lensing signal of an ensemble of filaments between groups and clusters of galaxies. Specifically, we detect the weak lensing signal, using CFHTLenS galaxy ellipticities, from stacked filaments between Sloan Digital Sky Survey (SDSS)-III/Baryon Oscillation Spectroscopic Survey luminous red galaxies (LRGs). As a control, we compare the physical LRG pairs with projected LRG pairs that are more widely separated in redshift space. We detect the excess filament mass density in the projected pairs at the 5σ level, finding a mass of (1.6 ± 0.3) × 1013 M⊙ for a stacked filament region 7.1 h-1 Mpc long and 2.5 h-1 Mpc wide. This filament signal is compared with a model based on the three-point galaxy-galaxy-convergence correlation function, as developed in Clampitt et al., yielding reasonable agreement.

  14. Unconventional actin conformations localize on intermediate filaments in mitosis

    International Nuclear Information System (INIS)

    Hubert, Thomas; Vandekerckhove, Joel; Gettemans, Jan

    2011-01-01

    Research highlights: → Unconventional actin conformations colocalize with vimentin on a cage-like structure in metaphase HEK 293T cells. → These conformations are detected with the anti-actin antibodies 1C7 ('lower dimer') and 2G2 ('nuclear actin'), but not C4 (monomeric actin). → Mitotic unconventional actin cables are independent of filamentous actin or microtubules. → Unconventional actin colocalizes with vimentin on a nocodazole-induced perinuclear dense mass of cables. -- Abstract: Different structural conformations of actin have been identified in cells and shown to reside in distinct subcellular locations of cells. In this report, we describe the localization of actin on a cage-like structure in metaphase HEK 293T cells. Actin was detected with the anti-actin antibodies 1C7 and 2G2, but not with the anti-actin antibody C4. Actin contained in this structure is independent of microtubules and actin filaments, and colocalizes with vimentin. Taking advantage of intermediate filament collapse into a perinuclear dense mass of cables when microtubules are depolymerized, we were able to relocalize actin to such structures. We hypothesize that phosphorylation of intermediate filaments at mitosis entry triggers the recruitment of different actin conformations to mitotic intermediate filaments. Storage and partition of the nuclear actin and antiparallel 'lower dimer' actin conformations between daughter cells possibly contribute to gene transcription and transient actin filament dynamics at G1 entry.

  15. Design and optimize of 3-axis filament winding machine

    Science.gov (United States)

    Quanjin, Ma; Rejab, M. R. M.; Idris, M. S.; Bachtiar, B.; Siregar, J. P.; Harith, M. N.

    2017-10-01

    Filament winding technique is developed as the primary process for composite cylindrical structures fabrication at low cost. Fibres are wound on a rotating mandrel by a filament winding machine where resin impregnated fibres pass through a pay-out eye. This paper aims to develop and optimize a 3-axis, lightweight, practical, efficient, portable filament winding machine to satisfy the customer demand, which can fabricate pipes and round shape cylinders with resins. There are 3 main units on the 3-axis filament winding machine, which are the rotary unit, the delivery unit and control system unit. Comparison with previous existing filament winding machines in the factory, it has 3 degrees of freedom and can fabricate more complex shape specimens based on the mandrel shape and particular control system. The machine has been designed and fabricated on 3 axes movements with control system. The x-axis is for movement of the carriage, the y-axis is the rotation of mandrel and the z-axis is the movement of the pay-out eye. Cylindrical specimens with different dimensions and winding angles were produced. 3-axis automated filament winding machine has been successfully designed with simple control system.

  16. Effect of Filament Fineness on Composite Yarn Residual Torque

    Directory of Open Access Journals (Sweden)

    Sarıoğlu Esin

    2018-03-01

    Full Text Available Yarn residual torque or twist liveliness occurs when the twist is imparted to spin the fibers during yarn formation. It causes yarn snarling, which is an undesirable property and can lead the problems for further processes such as weaving and knitting. It affects the spirality of knitted fabrics and skewness of woven fabrics. Generally, yarn residual torque depends on yarn twist, yarn linear density, and fiber properties used. Composite yarns are widely produced to exploit two yarns with different properties such on optimum way at the same time and these yarns can be produced by wrapping sheath fibers around filament core fiber with a certain twist. In this study, the effect of filament fineness used as core component of composite yarn on residual torque was analyzed. Thus, the false twist textured polyester filament yarns with different filament fineness were used to produce composite yarns with different yarn count. The variance analysis was performed to determine the significance of twist liveliness of filament yarns and yarn count on yarn twist liveliness. Results showed that there is a statistically significant differences at significance level of α=0.05 between filament fineness and yarn residual torque of composite yarns.

  17. Filament winding technique, experiment and simulation analysis on tubular structure

    Science.gov (United States)

    Quanjin, Ma; Rejab, M. R. M.; Kaige, Jiang; Idris, M. S.; Harith, M. N.

    2018-04-01

    Filament winding process has emerged as one of the potential composite fabrication processes with lower costs. Filament wound products involve classic axisymmetric parts (pipes, rings, driveshafts, high-pressure vessels and storage tanks), non-axisymmetric parts (prismatic nonround sections and pipe fittings). Based on the 3-axis filament winding machine has been designed with the inexpensive control system, it is completely necessary to make a relative comparison between experiment and simulation on tubular structure. In this technical paper, the aim of this paper is to perform a dry winding experiment using the 3-axis filament winding machine and simulate winding process on the tubular structure using CADWIND software with 30°, 45°, 60° winding angle. The main result indicates that the 3-axis filament winding machine can produce tubular structure with high winding pattern performance with different winding angle. This developed 3-axis winding machine still has weakness compared to CAWIND software simulation results with high axes winding machine about winding pattern, turnaround impact, process error, thickness, friction impact etc. In conclusion, the 3-axis filament winding machine improvements and recommendations come up with its comparison results, which can intuitively understand its limitations and characteristics.

  18. Laser-induced filaments in the mid-infrared

    International Nuclear Information System (INIS)

    Zheltikov, A M

    2017-01-01

    Laser-induced filamentation in the mid-infrared gives rise to unique regimes of nonlinear wave dynamics and reveals in many ways unusual nonlinear-optical properties of materials in this frequency range. The λ 2 scaling of the self-focusing threshold P cr , with radiation wavelength λ , allows the laser powers transmitted by single mid-IR filaments to be drastically increased without the loss of beam continuity and spatial coherence. When extended to the mid-infrared, laser filamentation enables new methods of pulse compression. Often working around the universal physical limitations, it helps generate few-cycle and subcycle field waveforms within an extraordinarily broad range of peak powers, from just a few up to hundreds of P cr . As a part of a bigger picture, laser-induced filamentation in the mid-infrared offers important physical insights into the general properties of the nonlinear-optical response of matter as a function of the wavelength. Unlike their near-infrared counterparts, which can be accurately described within the framework of perturbative nonlinear optics, mid-infrared filaments often entangle perturbative and nonperturbative nonlinear-optical effects, showing clear signatures of strong-field optical physics. With the role of nonperturbative nonlinear-optical phenomena growing, as a general tendency, with the field intensity and the driver wavelength, extension of laser filamentation to even longer driver wavelengths, toward the long-wavelength infrared, promises a hic sunt dracones land. (topical review)

  19. Force-velocity measurements of a few growing actin filaments.

    Directory of Open Access Journals (Sweden)

    Coraline Brangbour

    2011-04-01

    Full Text Available The polymerization of actin in filaments generates forces that play a pivotal role in many cellular processes. We introduce a novel technique to determine the force-velocity relation when a few independent anchored filaments grow between magnetic colloidal particles. When a magnetic field is applied, the colloidal particles assemble into chains under controlled loading or spacing. As the filaments elongate, the beads separate, allowing the force-velocity curve to be precisely measured. In the widely accepted Brownian ratchet model, the transduced force is associated with the slowing down of the on-rate polymerization. Unexpectedly, in our experiments, filaments are shown to grow at the same rate as when they are free in solution. However, as they elongate, filaments are more confined in the interspace between beads. Higher repulsive forces result from this higher confinement, which is associated with a lower entropy. In this mechanism, the production of force is not controlled by the polymerization rate, but is a consequence of the restriction of filaments' orientational fluctuations at their attachment point.

  20. Quantitative analysis of UV-A shock and short term stress using iTRAQ, pseudo selective reaction monitoring (pSRM) and GC-MS based metabolite analysis of the cyanobacterium Nostoc punctiforme ATCC 29133.

    Science.gov (United States)

    Wase, Nishikant; Pham, Trong Khoa; Ow, Saw Yen; Wright, Phillip C

    2014-09-23

    A quantitative proteomics and metabolomics analysis was performed using iTRAQ, HPLC and GC-MS in the filamentous cyanobacterium Nostoc punctiforme ATCC 29133 to understand the effect of short and long term UV-A exposure. Changes in the proteome were measured for short-term stress (4-24h) using iTRAQ. Changes in the photosynthetic pigments and intracellular metabolites were observed at exposures of up to 7days (pigments) and up to 11days (intracellular metabolites). To assess iTRAQ measurement quality, pseudo selected reaction monitoring (pSRM) was used, with this confirming underestimation of protein abundance levels by iTRAQ. Our results suggest that short term UV-A radiation lowers the abundance of PS-I and PS-II proteins. We also observed an increase in abundance of intracellular redox homeostasis proteins and plastocyanin. Additionally, we observed statistically significant changes in scytonemin, Chlorophyll A, astaxanthin, zeaxanthin, and β-carotene. Assessment of intracellular metabolites showed significant changes in several, suggesting their potential role in the Nostoc's stress mitigation strategy. Cyanobacteria under UV-A radiation have reduced growth due to intensive damage to essential functions, but the organism shows a defense response by remodeling bioenergetics pathway, induction of the UV protection compound scytonemin and increased levels of proline and tyrosine as a mitigation response. The effect of UV-A radiation on the proteome and intracellular metabolites of N. punctiforme ATCC 29133 including photosynthetic pigments has been described. We also verify the expression of 13 iTRAQ quantified protein using LC-pSRM. Overall we observed that UV-A radiation has a drastic effect on the photosynthetic machinery, photosynthetic pigments and intracellular amino acids. As a mitigation strategy against UV-A radiation, proline, glycine, and tyrosine were accumulated. Copyright © 2014. Published by Elsevier B.V.

  1. Disintegration of an eruptive filament via interactions with quasi-separatrix layers

    Science.gov (United States)

    Liu, Rui; Chen, Jun; Wang, YuMing

    2018-06-01

    The disintegration of solar filaments via mass drainage is a frequently observed phenomenon during a variety of filament activities. It is generally considered that the draining of dense filament material is directed by both gravity and magnetic field, yet the detailed process remains elusive. Here we report on a partial filament eruption during which filament material drains downward to the surface not only along the filament's legs, but to a remote flare ribbon through a fan-out curtain-like structure. It is found that the magnetic configuration is characterized by two conjoining dome-like quasi-sepratrix layers (QSLs). The filament is located underneath one QSL dome, whose footprint apparently bounds the major flare ribbons resulting from the filament eruption, whereas the remote flare ribbon matches well with the other QSL dome's far-side footprint. We suggest that the interaction of the filament with the overlying QSLs results in the splitting and disintegration of the filament.

  2. Self-assembly of designed supramolecular magnetic filaments of different shapes

    Energy Technology Data Exchange (ETDEWEB)

    Novak, E.V. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Rozhkov, D.A., E-mail: d.a.rozhkov@gmail.com [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); Sanchez, P.A. [University of Vienna, Sensengasse 8, Vienna (Austria); Kantorovich, S.S. [Ural Federal University, Lenin Av. 51, Ekaterinburg (Russian Federation); University of Vienna, Sensengasse 8, Vienna (Austria)

    2017-06-01

    In the present work we study via molecular dynamics simulations filaments of ring and linear shape. Filaments are made of magnetic nanoparticles, possessing a point dipole in their centres. Particles in filaments are crosslinked in a particular way, so that the deviation of the neighbouring dipoles from the head-to-tail orientation is penalised by the bond. We show how the conformation of a single chain and ring filament changes on cooling for different lengths. We also study filament pairs, by fixing filaments at a certain distance and analysing the impact of inter-filament interaction on the equilibrium configurations. Our study opens a perspective to investigate the dispersions of filaments, both theoretically and numerically, by using effective potentials. - Highlights: • Single filament study. • Magnetic particles crosslinked in chains and rings. • Magnetic filament interactions.

  3. Local mat-forming cyanobacteria effectively facilitate decontamination of radioactive cesium in rice fields

    International Nuclear Information System (INIS)

    Yamamoto, Atsushi; Yoshida, Shigeru; Okumura, Hiroshi; Inagaki, Masayo; Yamanishi, Hirokuni; Ito, Tetsuo; Furukawa, Michio

    2015-01-01

    The most effective and widespread method to decontaminate radioactive cesium from the Fukushima Daiichi Nuclear Power Plant Disaster was peeling topsoil. But the method had problems, such as large amounts of discarded soil and large-scale work. In nature, cyanobacteria formed biomats on the ground surface and facilitated peeling topsoil when the biomats dried. The cyanobacteria-facilitating peeling decontamination method utilized these cyanobacterial properties. Cyanobacteria are located all over Japan and 'local' cyanobacteria could be used for decontamination without introducing new species. Utilizing cyanobacteria could decrease the amount of discarded soil to about 30% and downsize the execution-scale to individual locations. Cyanobacterial biomats were easily cultivated, especially in rice fields, by maintaining wet conditions and exposure to 100 - 83% solar radiation. Shading by a thin net was helpful in maintaining an environment suitable for cyanobacteria. Nowadays, to prevent uptake of radioactive cesium into rice, K + is usually added to fertilizer in rice fields. The K + fertilization in rice fields might also enhance cyanobacterial capture of radioactive cesium, because high concentrations of K + enhanced cyanobacterial uptake of Cs + . Cyanobacteria could also mitigate the risk of radioactive cesium moving away from a decontaminating rice field. Therefore, the cyanobacteria-facilitating peeling decontamination method was proposed as an easy and safe 'D.I.Y.' method for both farmers and the environment. Besides, plowing rice fields with water before peeling improved the efficiency of this method, because plowing increased the radioactive cesium concentration in the topsoil. (author)

  4. Giant quiescent solar filament observed with high-resolution spectroscopy

    Science.gov (United States)

    Kuckein, C.; Verma, M.; Denker, C.

    2016-05-01

    Aims: An extremely large filament was studied in various layers of the solar atmosphere. The inferred physical parameters and the morphological aspects are compared with smaller quiescent filaments. Methods: A giant quiet-Sun filament was observed with the high-resolution Echelle spectrograph at the Vacuum Tower Telescope at Observatorio del Teide, Tenerife, Spain, on 2011 November 15. A mosaic of spectra (ten maps of 100″ × 182″) was recorded simultaneously in the chromospheric absorption lines Hα and Na I D2. Physical parameters of the filament plasma were derived using cloud model (CM) inversions and line core fits. The spectra were complemented with full-disk filtergrams (He I λ10830 Å, Hα, and Ca II K) of the Chromospheric Telescope (ChroTel) and full-disk magnetograms of the Helioseismic and Magnetic Imager (HMI). Results: The filament had extremely large linear dimensions (~817 arcsec), which corresponds to about 658 Mm along a great circle on the solar surface. A total amount of 175119 Hα contrast profiles were inverted using the CM approach. The inferred mean line-of-sight (LOS) velocity, Doppler width, and source function were similar to previous works of smaller quiescent filaments. However, the derived optical thickness was higher. LOS velocity trends inferred from the Hα line core fits were in accord but weaker than those obtained with CM inversions. Signatures of counter-streaming flows were detected in the filament. The largest brightening conglomerates in the line core of Na I D2 coincided well with small-scale magnetic fields as seen by HMI. Mixed magnetic polarities were detected close to the ends of barbs. The computation of photospheric horizontal flows based on HMI magnetograms revealed flow kernels with a size of 5-8 Mm and velocities of 0.30-0.45 km s-1 at the ends of the filament. Conclusions: The physical properties of extremely large filaments are similar to their smaller counterparts, except for the optical thickness, which in

  5. Diurnal Regulation of Cellular Processes in the Cyanobacterium Synechocystis sp. Strain PCC 6803: Insights from Transcriptomic, Fluxomic, and Physiological Analyses

    Directory of Open Access Journals (Sweden)

    Rajib Saha

    2016-05-01

    Full Text Available Synechocystis sp. strain PCC 6803 is the most widely studied model cyanobacterium, with a well-developed omics level knowledgebase. Like the lifestyles of other cyanobacteria, that of Synechocystis PCC 6803 is tuned to diurnal changes in light intensity. In this study, we analyzed the expression patterns of all of the genes of this cyanobacterium over two consecutive diurnal periods. Using stringent criteria, we determined that the transcript levels of nearly 40% of the genes in Synechocystis PCC 6803 show robust diurnal oscillating behavior, with a majority of the transcripts being upregulated during the early light period. Such transcripts corresponded to a wide array of cellular processes, such as light harvesting, photosynthetic light and dark reactions, and central carbon metabolism. In contrast, transcripts of membrane transporters for transition metals involved in the photosynthetic electron transport chain (e.g., iron, manganese, and copper were significantly upregulated during the late dark period. Thus, the pattern of global gene expression led to the development of two distinct transcriptional networks of coregulated oscillatory genes. These networks help describe how Synechocystis PCC 6803 regulates its metabolism toward the end of the dark period in anticipation of efficient photosynthesis during the early light period. Furthermore, in silico flux prediction of important cellular processes and experimental measurements of cellular ATP, NADP(H, and glycogen levels showed how this diurnal behavior influences its metabolic characteristics. In particular, NADPH/NADP+ showed a strong correlation with the majority of the genes whose expression peaks in the light. We conclude that this ratio is a key endogenous determinant of the diurnal behavior of this cyanobacterium.

  6. The success of the cyanobacterium Cylindrospermopsis raciborskii in freshwaters is enhanced by the combined effects of light intensity and temperature

    Directory of Open Access Journals (Sweden)

    Sylvia Bonilla

    2016-06-01

    Full Text Available Toxic cyanobacterial blooms in freshwaters are thought to be a consequence of the combined effects of anthropogenic eutrophication and climate change. It is expected that climate change will affect water mixing regimes that alter the water transparency and ultimately the light environment for phytoplankton. Blooms of the potentially toxic cyanobacterium Cylindrospermopsis raciborskii are expanding from tropical towards temperate regions. Several hypotheses have been proposed to explain this expansion, including an increase in water temperature due to climate change and the high phenotypic plasticity of the species that allows it to exploit different light environments. We performed an analysis based on eight lakes in tropical, subtropical and temperate regions to examine the distribution and abundance of C. raciborskii in relation to water temperature and transparency. We then conducted a series of short-term factorial experiments that combined three temperatures and two light intensity levels using C. raciborskii cultures alone and in interaction with another cyanobacterium to identify its growth capacity. Our results from the field, in contrast to predictions, showed no differences in dominance (>40% to the total biovolume of C. raciborskii between climate regions. C. raciborskii was able to dominate the phytoplankton in a wide range of light environments (euphotic zone = 1.5 to 5 m, euphotic zone/mixing zone ratio <0.5 to >1.5. Moreover, C. raciborskii was capable of dominating the phytoplankton at low temperatures (<15°C. Our experimental results showed that C. raciborskii growing in interaction was enhanced by the increase of the temperature and light intensity. C. raciborskii growth in high light intensities and at a wide range of temperatures, suggests that any advantage that this species may derive from climate change that favors its dominance in the phytoplankton is likely due to changes in the light environment rather than changes in

  7. Diversity of the Marine Cyanobacterium Trichodesmium: Characterization of the Woods Hole Culture Collection and Quantification of Field Populations

    Science.gov (United States)

    2009-09-01

    stations on all four cruises; Fig. 5-4 C), and Plec - tonema sp. (North Pacific MP09-19, North Atlantic EN361-1, 2, 3; Fig. 5-4 D). Calothrix sp. was found in...under a chlorophyll filter; (C) ELF-labeled heterotrophic bacteria (Sta. MP09-16, 11 Aug 03, puff); (D) ELF-labeled cyanobacterium Plec - tonema sp...epiphyte of the pelagic diatom Chaetoceros (Foster and Zehr, 2006). While Plec - tonema is known to fix N2 only in lowered oxygen tension (Rippka et al

  8. Large amplitude oscillatory motion along a solar filament

    Science.gov (United States)

    Vršnak, B.; Veronig, A. M.; Thalmann, J. K.; Žic, T.

    2007-08-01

    Context: Large amplitude oscillations of solar filaments is a phenomenon that has been known for more than half a century. Recently, a new mode of oscillations, characterized by periodical plasma motions along the filament axis, was discovered. Aims: We analyze such an event, recorded on 23 January 2002 in Big Bear Solar Observatory Hα filtergrams, to infer the triggering mechanism and the nature of the restoring force. Methods: Motion along the filament axis of a distinct buldge-like feature was traced, to quantify the kinematics of the oscillatory motion. The data were fitted by a damped sine function to estimate the basic parameters of the oscillations. To identify the triggering mechanism, morphological changes in the vicinity of the filament were analyzed. Results: The observed oscillations of the plasma along the filament were characterized by an initial displacement of 24 Mm, an initial velocity amplitude of 51 km s-1, a period of 50 min, and a damping time of 115 min. We interpret the trigger in terms of poloidal magnetic flux injection by magnetic reconnection at one of the filament legs. The restoring force is caused by the magnetic pressure gradient along the filament axis. The period of oscillations, derived from the linearized equation of motion (harmonic oscillator) can be expressed as P=π√{2}L/v_Aϕ≈4.4L/v_Aϕ, where v_Aϕ =Bϕ0/√μ_0ρ represents the Alfvén speed based on the equilibrium poloidal field Bϕ0. Conclusions: Combination of our measurements with some previous observations of the same kind of oscillations shows good agreement with the proposed interpretation. Movie to Fig. 1 is only available in electronic form at http://www.aanda.org

  9. Highly plastic genome of Microcystis aeruginosa PCC 7806, a ubiquitous toxic freshwater cyanobacterium

    Directory of Open Access Journals (Sweden)

    Latifi Amel

    2008-06-01

    Full Text Available Abstract Background The colonial cyanobacterium Microcystis proliferates in a wide range of freshwater ecosystems and is exposed to changing environmental factors during its life cycle. Microcystis blooms are often toxic, potentially fatal to animals and humans, and may cause environmental problems. There has been little investigation of the genomics of these cyanobacteria. Results Deciphering the 5,172,804 bp sequence of Microcystis aeruginosa PCC 7806 has revealed the high plasticity of its genome: 11.7% DNA repeats containing more than 1,000 bases, 6.8% putative transposases and 21 putative restriction enzymes. Compared to the genomes of other cyanobacterial lineages, strain PCC 7806 contains a large number of atypical genes that may have been acquired by lateral transfers. Metabolic pathways, such as fermentation and a methionine salvage pathway, have been identified, as have genes for programmed cell death that may be related to the rapid disappearance of Microcystis blooms in nature. Analysis of the PCC 7806 genome also reveals striking novel biosynthetic features that might help to elucidate the ecological impact of secondary metabolites and lead to the discovery of novel metabolites for new biotechnological applications. M. aeruginosa and other large cyanobacterial genomes exhibit a rapid loss of synteny in contrast to other microbial genomes. Conclusion Microcystis aeruginosa PCC 7806 appears to have adopted an evolutionary strategy relying on unusual genome plasticity to adapt to eutrophic freshwater ecosystems, a property shared by another strain of M. aeruginosa (NIES-843. Comparisons of the genomes of PCC 7806 and other cyanobacterial strains indicate that a similar strategy may have also been used by the marine strain Crocosphaera watsonii WH8501 to adapt to other ecological niches, such as oligotrophic open oceans.

  10. Using oxidized liquid and solid human waste as nutrients for Chlorella vulgaris and cyanobacterium Oscillatoria deflexa

    Science.gov (United States)

    Trifonov, Sergey V.; Kalacheva, Galina; Tirranen, Lyalya; Gribovskaya, Iliada

    At stationary terrestrial and space stations with closed and partially closed substance exchange not only plants, but also algae can regenerate atmosphere. Their biomass can be used for feeding Daphnia and Moina species, which, in their turn, serve as food for fish. In addition, it is possible to use algae for production of biological fuel. We suggested two methods of human waste mineralization: dry (evaporation with subsequent incineration in a muffle furnace) and wet (oxidation in a reactor using hydrogen peroxide). The research task was to prepare nutrient media for green alga Chlorella vulgaris and cyanobacterium Oscillatoria deflexa using liquid human waste mineralized by dry method, and to prepare media for chlorella on the basis of 1) liquid and 2) liquid and solid human waste mineralized by wet method. The algae were grown in batch culture in a climate chamber with the following parameters: illumination 7 klx, temperature 27-30 (°) C, culture density 1-2 g/l of dry weight. The control for chlorella was Tamiya medium, pH-5, and for oscillstoria — Zarrouk medium, pH-10. Maximum permissible concentrations of NaCl, Cl, urea (NH _{2}) _{2}CO, and native urine were established for algae. Missing ingredients (such as salts and acids) for experimental nutrient media were determined: their addition made it possible to obtain the biomass production not less than that in the control. The estimation was given of the mineral and biochemical composition of algae grown on experimental media. Microbiological test revealed absence of foreign microbial flora in experimental cultures.

  11. Ethylene Regulates the Physiology of the Cyanobacterium Synechocystis sp. PCC 6803 via an Ethylene Receptor.

    Science.gov (United States)

    Lacey, Randy F; Binder, Brad M

    2016-08-01

    Ethylene is a plant hormone that plays a crucial role in the growth and development of plants. The ethylene receptors in plants are well studied, and it is generally assumed that they are found only in plants. In a search of sequenced genomes, we found that many bacterial species contain putative ethylene receptors. Plants acquired many proteins from cyanobacteria as a result of the endosymbiotic event that led to chloroplasts. We provide data that the cyanobacterium Synechocystis (Synechocystis sp. PCC 6803) has a functional receptor for ethylene, Synechocystis Ethylene Response1 (SynEtr1). We first show that SynEtr1 directly binds ethylene. Second, we demonstrate that application of ethylene to Synechocystis cells or disruption of the SynEtr1 gene affects several processes, including phototaxis, type IV pilus biosynthesis, photosystem II levels, biofilm formation, and spontaneous cell sedimentation. Our data suggest a model where SynEtr1 inhibits downstream signaling and ethylene inhibits SynEtr1. This is similar to the inverse-agonist model of ethylene receptor signaling proposed for plants and suggests a conservation of structure and function that possibly originated over 1 billion years ago. Prior research showed that SynEtr1 also contains a light-responsive phytochrome-like domain. Thus, SynEtr1 is a bifunctional receptor that mediates responses to both light and ethylene. To our knowledge, this is the first demonstration of a functional ethylene receptor in a nonplant species and suggests that that the perception of ethylene is more widespread than previously thought. © 2016 American Society of Plant Biologists. All Rights Reserved.

  12. Arsenic Demethylation by a C·As Lyase in Cyanobacterium Nostoc sp. PCC 7120.

    Science.gov (United States)

    Yan, Yu; Ye, Jun; Xue, Xi-Mei; Zhu, Yong-Guan

    2015-12-15

    Arsenic, a ubiquitous toxic substance, exists mainly as inorganic forms in the environment. It is perceived that organoarsenicals can be demethylated and degraded into inorganic arsenic by microorganisms. Few studies have focused on the mechanism of arsenic demethylation in bacteria. Here, we investigated arsenic demethylation in a typical freshwater cyanobacterium Nostoc sp. PCC 7120. This bacterium was able to demethylate monomethylarsenite [MAs(III)] rapidly to arsenite [As(III)] and also had the ability to demethylate monomethylarsenate [MAs(V)] to As(III). The NsarsI encoding a C·As lyase responsible for MAs(III) demethylation was cloned from Nostoc sp. PCC 7120 and heterologously expressed in an As-hypersensitive strain Escherichia coli AW3110 (ΔarsRBC). Expression of NsarsI was shown to confer MAs(III) resistance through arsenic demethylation. The purified NsArsI was further identified and functionally characterized in vitro. NsArsI existed mainly as the trimeric state, and the kinetic data were well-fit to the Hill equation with K0.5 = 7.55 ± 0.33 μM for MAs(III), Vmax = 0.79 ± 0.02 μM min(-1), and h = 2.7. Both of the NsArsI truncated derivatives lacking the C-terminal 10 residues (ArsI10) or 23 residues (ArsI23) had a reduced ability of MAs(III) demethylation. These results provide new insights for understanding the important role of cyanobacteria in arsenic biogeochemical cycling in the environment.

  13. Isolation and in silico analysis of Fe-superoxide dismutase in the cyanobacterium Nostoc commune.

    Science.gov (United States)

    Kesheri, Minu; Kanchan, Swarna; Richa; Sinha, Rajeshwar P

    2014-12-15

    Cyanobacteria are known to endure various stress conditions due to the inbuilt potential for oxidative stress alleviation owing to the presence of an array of antioxidants. The present study shows that Antarctic cyanobacterium Nostoc commune possesses two antioxidative enzymes viz., superoxide dismutase (SOD) and catalase that jointly cope with environmental stresses prevailing at its natural habitat. Native-PAGE analysis illustrates the presence of a single prominent isoform recognized as Fe-SOD and three distinct isoforms of catalase. The protein sequence of Fe-SOD in N. commune retrieved from NCBI protein sequence database was used for in silico analysis. 3D structure of N. commune was predicted by comparative modeling using MODELLER 9v11. Further, this model was validated for its quality by Ramachandran plot, ERRAT, Verify 3D and ProSA-web which revealed good structure quality of the model. Multiple sequence alignment showed high conservation in N and C-terminal domain regions along with all metal binding positions in Fe-SOD which were also found to be highly conserved in all 28 cyanobacterial species under study, including N. commune. In silico prediction of isoelectric point and molecular weight of Fe-SOD was found to be 5.48 and 22,342.98Da respectively. The phylogenetic tree revealed that among 28 cyanobacterial species, Fe-SOD in N. commune was the closest evolutionary homolog of Fe-SOD in Nostoc punctiforme as evident by strong bootstrap value. Thus, N. commune may serve as a good biological model for studies related to survival of life under extreme conditions prevailing at the Antarctic region. Moreover cyanobacteria may be exploited for biochemical and biotechnological applications of enzymatic antioxidants. Copyright © 2014 Elsevier B.V. All rights reserved.

  14. Enhanced biohydrogen production by the N{sub 2}-fixing cyanobacterium Anabaena siamensis strain TISTR 8012

    Energy Technology Data Exchange (ETDEWEB)

    Khetkorn, Wanthanee [Program of Biotechnology, Faculty of Science, Chulalongkorn University, Bangkok, 10330 (Thailand); Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Bangkok, 10330 (Thailand); Department of Photochemistry and Molecular Science, Uppsala University, Box 523, SE-75120, Uppsala (Sweden); Lindblad, Peter [Department of Photochemistry and Molecular Science, Uppsala University, Box 523, SE-75120, Uppsala (Sweden); Incharoensakdi, Aran [Laboratory of Cyanobacterial Biotechnology, Department of Biochemistry, Faculty of Science, Chulalongkorn University, Phayathai Road, Bangkok, 10330 (Thailand)

    2010-12-15

    The efficiency of hydrogen production depends on several factors. We focused on external conditions leading to enhanced hydrogen production when using the N{sub 2}-fixing cyanobacterium Anabaena siamensis TISTR 8012, a novel strain isolated from a rice paddy field in Thailand. In this study, we controlled key factors affecting hydrogen production such as cell age, light intensity, time of light incubation and source of carbon. Our results showed an enhanced hydrogen production when cells, at log phase, were adapted under N{sub 2}-fixing condition using 0.5% fructose as carbon source and a continuous illumination of 200 {mu}E m{sup -2} s{sup -1} for 12 h under anaerobic incubation. The maximum hydrogen production rate was 32 {mu}mol H{sub 2} mg chl a{sup -1} h{sup -1}. This rate was higher than that observed in the model organisms Anabaena PCC 7120, Nostoc punctiforme ATCC 29133 and Synechocystis PCC 6803. This higher production was likely caused by a higher nitrogenase activity since we observed an upregulation of nifD. The production did not increase after 12 h which was probably due to an increased activity of the uptake hydrogenase as evidenced by an increased hupL transcript level. Interestingly, a proper adjustment of light conditions such as intensity and duration is important to minimize both the photodamage of the cells and the uptake hydrogenase activity. Our results indicate that A. siamensis TISTR 8012 has a high potential for hydrogen production with the ability to utilize sugars as substrate to produce hydrogen. (author)

  15. The genome of Cyanothece 51142, a unicellular diazotrophic cyanobacterium important in the marine nitrogen cycle

    Energy Technology Data Exchange (ETDEWEB)

    Welsh, Eric A.; Liberton, Michelle L.; Stockel, Jana; Loh, Thomas; Elvitigala, Thanura R.; Wang, Chunyan; Wollam, Aye; Fulton, Robert S.; Clifton, Sandra W.; Jacobs, Jon M.; Aurora, Rajeev; Ghosh, Bijoy K.; Sherman, Louis A.; Smith, Richard D.; Wilson, Richard K.; Pakrasi, Himadri B.

    2008-09-30

    Cyanobacteria are oxygenic photosynthetic bacteria that have significant roles in global biological carbon sequestration and oxygen production. They occupy a diverse range of habitats, from open ocean, to hot springs, deserts, and arctic waters. Cyanobacteria are known as the progenitors of the chloroplasts of plants and algae, and are the simplest known organisms to exhibit circadian behavior4. Cyanothece sp. ATCC 51142 is a unicellular marine cyanobacterium capable of N2-fixation, a process that is biochemically incompatible with oxygenic photosynthesis. To resolve this problem, Cyanothece performs photosynthesis during the day and nitrogen fixation at night, thus temporally separating these processes in the same cell. The genome of Cyanothece 51142 was completely sequenced and found to contain a unique arrangement of one large circular chromosome, four small plasmids, and one linear chromosome, the first report of such a linear element in a photosynthetic bacterium. Annotation of the Cyanothece genome was aided by the use of highthroughput proteomics data, enabling the reclassification of 25% of the proteins with no informative sequence homology. Phylogenetic analysis suggests that nitrogen fixation is an ancient process that arose early in evolution and has subsequently been lost in many cyanobacterial strains. In cyanobacterial cells, the circadian clock influences numerous processes, including carbohydrate synthesis, nitrogen fixation, photosynthesis, respiration, and the cell division cycle. During a diurnal period, Cyanothece cells actively accumulate and degrade different storage inclusion bodies for the products of photosynthesis and N2-fixation. This ability to utilize metabolic compartmentalization and energy storage makes Cyanothece an ideal system for bioenergy research, as well as studies of how a unicellular organism balances multiple, often incompatible, processes in the same cell.

  16. A Salt-Inducible Mn-Catalase (KatB) Protects Cyanobacterium from Oxidative Stress.

    Science.gov (United States)

    Chakravarty, Dhiman; Banerjee, Manisha; Bihani, Subhash C; Ballal, Anand

    2016-02-01

    Catalases, enzymes that detoxify H2O2, are widely distributed in all phyla, including cyanobacteria. Unlike the heme-containing catalases, the physiological roles of Mn-catalases remain inadequately characterized. In the cyanobacterium Anabaena, pretreatment of cells with NaCl resulted in unusually enhanced tolerance to oxidative stress. On exposure to H2O2, the NaCl-treated Anabaena showed reduced formation of reactive oxygen species, peroxides, and oxidized proteins than the control cells (i.e. not treated with NaCl) exposed to H2O2. This protective effect correlated well with the substantial increase in production of KatB, a Mn-catalase. Addition of NaCl did not safeguard the katB mutant from H2O2, suggesting that KatB was indeed responsible for detoxifying the externally added H2O2. Moreover, Anabaena deficient in KatB was susceptible to oxidative effects of salinity stress. The katB gene was strongly induced in response to osmotic stress or desiccation. Promoter-gfp analysis showed katB to be expressed only in the vegetative cells but not in heterocysts. Biochemically, KatB was an efficient, robust catalase that remained active in the presence of high concentrations of NaCl. Our findings unravel the role of Mn-catalase in acclimatization to salt/oxidative stress and demonstrate that the oxidative stress resistance of an organism can be enhanced by a simple compound such as NaCl. © 2016 American Society of Plant Biologists. All Rights Reserved.

  17. Dependence of the cyanobacterium Prochlorococcus on hydrogen peroxide scavenging microbes for growth at the ocean's surface.

    Directory of Open Access Journals (Sweden)

    J Jeffrey Morris

    2011-02-01

    Full Text Available The phytoplankton community in the oligotrophic open ocean is numerically dominated by the cyanobacterium Prochlorococcus, accounting for approximately half of all photosynthesis. In the illuminated euphotic zone where Prochlorococcus grows, reactive oxygen species are continuously generated via photochemical reactions with dissolved organic matter. However, Prochlorococcus genomes lack catalase and additional protective mechanisms common in other aerobes, and this genus is highly susceptible to oxidative damage from hydrogen peroxide (HOOH. In this study we showed that the extant microbial community plays a vital, previously unrecognized role in cross-protecting Prochlorococcus from oxidative damage in the surface mixed layer of the oligotrophic ocean. Microbes are the primary HOOH sink in marine systems, and in the absence of the microbial community, surface waters in the Atlantic and Pacific Ocean accumulated HOOH to concentrations that were lethal for Prochlorococcus cultures. In laboratory experiments with the marine heterotroph Alteromonas sp., serving as a proxy for the natural community of HOOH-degrading microbes, bacterial depletion of HOOH from the extracellular milieu prevented oxidative damage to the cell envelope and photosystems of co-cultured Prochlorococcus, and facilitated the growth of Prochlorococcus at ecologically-relevant cell concentrations. Curiously, the more recently evolved lineages of Prochlorococcus that exploit the surface mixed layer niche were also the most sensitive to HOOH. The genomic streamlining of these evolved lineages during adaptation to the high-light exposed upper euphotic zone thus appears to be coincident with an acquired dependency on the extant HOOH-consuming community. These results underscore the importance of (indirect biotic interactions in establishing niche boundaries, and highlight the impacts that community-level responses to stress may have in the ecological and evolutionary outcomes for co

  18. Phosphoproteome of the cyanobacterium Synechocystis sp. PCC 6803 and its dynamics during nitrogen starvation.

    Directory of Open Access Journals (Sweden)

    Philipp eSpät

    2015-03-01

    Full Text Available Cyanobacteria have shaped the earth’s biosphere as the first oxygenic photoautotrophs and still play an important role in many ecosystems. The ability to adapt to changing environmental conditions is an essential characteristic in order to ensure survival. To this end, numerous studies have shown that bacteria use protein post-translational modifications such as Ser/Thr/Tyr phosphorylation in cell signalling, adaptation and regulation. Nevertheless, our knowledge of cyanobacterial phosphoproteomes and their dynamic response to environmental stimuli is relatively limited. In this study, we applied gel-free methods and high accuracy mass spectrometry towards the unbiased detection of Ser/Thr/Tyr phosphorylation events in the model cyanobacterium Synechocystis sp. PCC 6803. We could identify over 300 phosphorylation events in cultures grown on nitrate as exclusive nitrogen source. Chemical dimethylation labelling was applied to investigate proteome and phosphoproteome dynamics during nitrogen starvation. Our dataset describes the most comprehensive (phosphoproteome of Synechocystis to date, identifying 2,382 proteins and 183 phosphorylation events and quantifying 2,111 proteins and 148 phosphorylation events during nitrogen starvation. Global protein phosphorylation levels were increased in response to nitrogen depletion after 24 hours. Among the proteins with increased phosphorylation, the PII signalling protein showed the highest fold-change, serving as positive control. Other proteins with increased phosphorylation levels comprised functions in photosynthesis and in carbon and nitrogen metabolism. This study reveals dynamics of Synechocystis phosphoproteome in response to environmental stimuli and suggests an important role of protein Ser/Thr/Tyr phosphorylation in fundamental mechanisms of homeostatic control in cyanobacteria.

  19. Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament

    Energy Technology Data Exchange (ETDEWEB)

    Ching, Tao-Chung; Lai, Shih-Ping [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China); Zhang, Qizhou; Girart, Josep M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge MA 02138 (United States); Qiu, Keping [School of Astronomy and Space Science, Nanjing University, 163 Xianlin Avenue, Nanjing 210023 (China); Liu, Hauyu B., E-mail: chingtaochung@gmail.com [European Southern Observatory (ESO), Karl-Schwarzschild-Str. 2, D-85748 Garching (Germany)

    2017-04-01

    We present Submillimeter Array 880 μ m dust polarization observations of six massive dense cores in the DR21 filament. The dust polarization shows complex magnetic field structures in the massive dense cores with sizes of 0.1 pc, in contrast to the ordered magnetic fields of the parsec-scale filament. The major axes of the massive dense cores appear to be aligned either parallel or perpendicular to the magnetic fields of the filament, indicating that the parsec-scale magnetic fields play an important role in the formation of the massive dense cores. However, the correlation between the major axes of the cores and the magnetic fields of the cores is less significant, suggesting that during the core formation, the magnetic fields below 0.1 pc scales become less important than the magnetic fields above 0.1 pc scales in supporting a core against gravity. Our analysis of the angular dispersion functions of the observed polarization segments yields a plane-of-sky magnetic field strength of 0.4–1.7 mG for the massive dense cores. We estimate the kinematic, magnetic, and gravitational virial parameters of the filament and the cores. The virial parameters show that the gravitational energy in the filament dominates magnetic and kinematic energies, while the kinematic energy dominates in the cores. Our work suggests that although magnetic fields may play an important role in a collapsing filament, the kinematics arising from gravitational collapse must become more important than magnetic fields during the evolution from filaments to massive dense cores.

  20. A comparison study of a solar active-region eruptive filament and a neighboring non-eruptive filament

    Science.gov (United States)

    Jiang, Chao-Wei; Wu, Shi-Tsan; Feng, Xue-Shang; Hu, Qiang

    2016-01-01

    Solar active region (AR) 11283 is a very magnetically complex region and it has produced many eruptions. However, there exists a non-eruptive filament in the plage region just next to an eruptive one in the AR, which gives us an opportunity to perform a comparison analysis of these two filaments. The coronal magnetic field extrapolated using our CESE-MHD-NLFFF code reveals that two magnetic flux ropes (MFRs) exist in the same extrapolation box supporting these two filaments, respectively. Analysis of the magnetic field shows that the eruptive MFR contains a bald-patch separatrix surface (BPSS) cospatial very well with a pre-eruptive EUV sigmoid, which is consistent with the BPSS model for coronal sigmoids. The magnetic dips of the non-eruptive MFRs match Hα observation of the non-eruptive filament strikingly well, which strongly supports the MFR-dip model for filaments. Compared with the non-eruptive MFR/filament (with a length of about 200 Mm), the eruptive MFR/filament is much smaller (with a length of about 20 Mm), but it contains most of the magnetic free energy in the extrapolation box and holds a much higher free energy density than the non-eruptive one. Both the MFRs are weakly twisted and cannot trigger kink instability. The AR eruptive MFR is unstable because its axis reaches above a critical height for torus instability, at which the overlying closed arcades can no longer confine the MFR stably. On the contrary, the quiescent MFR is very firmly held by its overlying field, as its axis apex is far below the torus-instability threshold height. Overall, this comparison investigation supports that an MFR can exist prior to eruption and the ideal MHD instability can trigger an MFR eruption.

  1. A comparison study of a solar active-region eruptive filament and a neighboring non-eruptive filament

    International Nuclear Information System (INIS)

    Jiang, Chao-Wei; Feng, Xue-Shang; Wu, Shi-Tsan; Hu, Qiang

    2016-01-01

    Solar active region (AR) 11283 is a very magnetically complex region and it has produced many eruptions. However, there exists a non-eruptive filament in the plage region just next to an eruptive one in the AR, which gives us an opportunity to perform a comparison analysis of these two filaments. The coronal magnetic field extrapolated using our CESE–MHD–NLFFF code reveals that two magnetic flux ropes (MFRs) exist in the same extrapolation box supporting these two filaments, respectively. Analysis of the magnetic field shows that the eruptive MFR contains a bald-patch separatrix surface (BPSS) cospatial very well with a pre-eruptive EUV sigmoid, which is consistent with the BPSS model for coronal sigmoids. The magnetic dips of the non-eruptive MFRs match Hα observation of the non-eruptive filament strikingly well, which strongly supports the MFR-dip model for filaments. Compared with the non-eruptive MFR/filament (with a length of about 200 Mm), the eruptive MFR/filament is much smaller (with a length of about 20 Mm), but it contains most of the magnetic free energy in the extrapolation box and holds a much higher free energy density than the non-eruptive one. Both the MFRs are weakly twisted and cannot trigger kink instability. The AR eruptive MFR is unstable because its axis reaches above a critical height for torus instability, at which the overlying closed arcades can no longer confine the MFR stably. On the contrary, the quiescent MFR is very firmly held by its overlying field, as its axis apex is far below the torus-instability threshold height. Overall, this comparison investigation supports that an MFR can exist prior to eruption and the ideal MHD instability can trigger an MFR eruption. (paper)

  2. A filament of dark matter between two clusters of galaxies.

    Science.gov (United States)

    Dietrich, Jörg P; Werner, Norbert; Clowe, Douglas; Finoguenov, Alexis; Kitching, Tom; Miller, Lance; Simionescu, Aurora

    2012-07-12

    It is a firm prediction of the concordance cold-dark-matter cosmological model that galaxy clusters occur at the intersection of large-scale structure filaments. The thread-like structure of this 'cosmic web' has been traced by galaxy redshift surveys for decades. More recently, the warm–hot intergalactic medium (a sparse plasma with temperatures of 10(5) kelvin to 10(7) kelvin) residing in low-redshift filaments has been observed in emission and absorption. However, a reliable direct detection of the underlying dark-matter skeleton, which should contain more than half of all matter, has remained elusive, because earlier candidates for such detections were either falsified or suffered from low signal-to-noise ratios and unphysical misalignments of dark and luminous matter. Here we report the detection of a dark-matter filament connecting the two main components of the Abell 222/223 supercluster system from its weak gravitational lensing signal, both in a non-parametric mass reconstruction and in parametric model fits. This filament is coincident with an overdensity of galaxies and diffuse, soft-X-ray emission, and contributes a mass comparable to that of an additional galaxy cluster to the total mass of the supercluster. By combining this result with X-ray observations, we can place an upper limit of 0.09 on the hot gas fraction (the mass of X-ray-emitting gas divided by the total mass) in the filament.

  3. Rapid Formation and Disappearance of a Filament Barb

    Science.gov (United States)

    Joshi, Anand D.; Srivastava, Nandita; Mathew, Shibu K.; Martin, Sara F.

    2013-11-01

    We present observations of an activated quiescent filament obtained in Hα from the high-resolution Dutch Open Telescope (DOT) on 20 August 2010. The filament developed a barb in 10 min, which disappeared within the next 35 min. A data set from the DOT spanning 2 h was used to analyse this event. Line-of-sight velocity maps were constructed from the Doppler images, which reveal flows in filament spine during this period. Photospheric magnetograms were used from the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO) to determine the changes in magnetic flux in the region surrounding the barb location. The analysis shows flows in the filament spine towards the barb location preceding its formation, and flows in the barb towards the spine during its disappearance. Magnetograms reveal patches of minority polarity flux close to the end of the barb at its greatest elongation. The flows in the spine and barbs are along numerous threads that compose these typical filament structures. The flows are consistent with field-aligned threads and demonstrate that the replacement time of the mass in barbs, and by inference, in the spine is very rapid.

  4. High-Resolution Observations of a Filament showing Activated Barb

    Science.gov (United States)

    Joshi, Anand; Martin, Sara F.; Mathew, Shibu; Srivastava, Nandita

    2012-07-01

    Analysis of a filament showing an activated barb using observations from the Dutch Open Telescope (DOT) on 2010 August 20 are presented. The DOT takes Doppler images in Hα, among other wavelengths, in a region about 110 × 110 arcsec^{2} in area, at a cadence of 30~seconds. The offline image restoration technique of speckle reconstruction is applied to obtain diffraction limited images. The filament developed a new barb in 10~minutes, which disappeared within the next 35~minutes. Such a rapid formation and disappearance of a filament barb is unusual, and has not been reported earlier. Line-of-sight velocity maps were constructed from the Doppler images of the target filament. We observe flows in the filament spine towards the barb location prior to its formation, and flows in the barb towards the spine during its disappearance. Photospheric magnetograms from Heliospheric Magnetic Imager on board the Solar Dynamics Observatory, at a cadence of 45~seconds, were used to determine the changes in magnetic flux in the region surrounding the barb location. The variation of magnetic flux in this duration supports the view that barbs are rooted in minor magnetic polarity. Our analysis shows that barbs can be short-lived and formation and disappearance of the barb was associated with cancellation of magnetic flux.

  5. Morphological indictors of the chirality of solar filaments

    Science.gov (United States)

    Filippov, B. P.

    2017-10-01

    There is no doubt that the structural features of filaments reflect properties of their magnetic fields, such as chirality and helicity. However, the interpretation of some morphological features can lead to incorrect conclusions when the observing time is limited and the spatial resolution is insufficiently high. In spite of the relative constancy of their overall shapes, filaments are dynamical formations with inhomogeneities moving along the threads making them up. Therefore, it is possible to observe material concentrated not only in magnetic traps, but also along curved arcs. Difficulties often arise in determining the chirality of filaments with anomalous "barbs"; i.e., those whose jagged side is located on the opposite side of the axis compared to most ("normal") filaments. A simple model is used to show that anomalous barbs can exist in an ordinary magnetic flux rope, with the threads of its fine structure oriented nearly perpendicular to its length. A careful analysis of images with the maximum available spatial resolution and with information about temporal dynamics, together with comparisons with observations in various spectral lines, can enable a correct determination of the chirality of filaments.

  6. Intermediate Filaments at the Junction of Mechanotransduction, Migration, and Development

    Directory of Open Access Journals (Sweden)

    Rucha Sanghvi-Shah

    2017-09-01

    Full Text Available Mechanically induced signal transduction has an essential role in development. Cells actively transduce and respond to mechanical signals and their internal architecture must manage the associated forces while also being dynamically responsive. With unique assembly-disassembly dynamics and physical properties, cytoplasmic intermediate filaments play an important role in regulating cell shape and mechanical integrity. While this function has been recognized and appreciated for more than 30 years, continually emerging data also demonstrate important roles of intermediate filaments in cell signal transduction. In this review, with a particular focus on keratins and vimentin, the relationship between the physical state of intermediate filaments and their role in mechanotransduction signaling is illustrated through a survey of current literature. Association with adhesion receptors such as cadherins and integrins provides a critical interface through which intermediate filaments are exposed to forces from a cell's environment. As a consequence, these cytoskeletal networks are posttranslationally modified, remodeled and reorganized with direct impacts on local signal transduction events and cell migratory behaviors important to development. We propose that intermediate filaments provide an opportune platform for cells to both cope with mechanical forces and modulate signal transduction.

  7. Automatic Segmentation and Quantification of Filamentous Structures in Electron Tomography.

    Science.gov (United States)

    Loss, Leandro A; Bebis, George; Chang, Hang; Auer, Manfred; Sarkar, Purbasha; Parvin, Bahram

    2012-10-01

    Electron tomography is a promising technology for imaging ultrastructures at nanoscale resolutions. However, image and quantitative analyses are often hindered by high levels of noise, staining heterogeneity, and material damage either as a result of the electron beam or sample preparation. We have developed and built a framework that allows for automatic segmentation and quantification of filamentous objects in 3D electron tomography. Our approach consists of three steps: (i) local enhancement of filaments by Hessian filtering; (ii) detection and completion (e.g., gap filling) of filamentous structures through tensor voting; and (iii) delineation of the filamentous networks. Our approach allows for quantification of filamentous networks in terms of their compositional and morphological features. We first validate our approach using a set of specifically designed synthetic data. We then apply our segmentation framework to tomograms of plant cell walls that have undergone different chemical treatments for polysaccharide extraction. The subsequent compositional and morphological analyses of the plant cell walls reveal their organizational characteristics and the effects of the different chemical protocols on specific polysaccharides.

  8. Developments in hot-filament metal oxide deposition (HFMOD)

    International Nuclear Information System (INIS)

    Durrant, Steven F.; Trasferetti, Benedito C.; Scarminio, Jair; Davanzo, Celso U.; Rouxinol, Francisco P.M.; Gelamo, Rogerio V.; Bica de Moraes, Mario A.

    2008-01-01

    Hot-filament metal oxide deposition (HFMOD) is a variant of conventional hot-filament chemical vapor deposition (HFCVD) recently developed in our laboratory and successfully used to obtain high-quality, uniform films of MO x , WO x and VO x . The method employs the controlled oxidation of a filament of a transition metal heated to 1000 deg. C or more in a rarefied oxygen atmosphere (typically, of about 1 Pa). Metal oxide vapor formed on the surface of the filament is transported a few centimetres to deposit on a suitable substrate. Key system parameters include the choice of filament material and diameter, the applied current and the partial pressures of oxygen in the chamber. Relatively high film deposition rates, such as 31 nm min -1 for MoO x , are obtained. The film stoichiometry depends on the exact deposition conditions. MoO x films, for example, present a mixture of MoO 2 and MoO 3 phases, as revealed by XPS. As determined by Li + intercalation using an electrochemical cell, these films also show a colouration efficiency of 19.5 cm 2 C -1 at a wavelength of 700 nm. MO x and WO x films are promising in applications involving electrochromism and characteristics of their colouring/bleaching cycles are presented. The chemical composition and structure of VO x films examined using IRRAS (infrared reflection-absorption spectroscopy), RBS (Rutherford backscattering spectrometry) and XPS (X-ray photoelectron spectrometry) are also presented

  9. Hot Ta filament resistance in-situ monitoring under silane containing atmosphere

    International Nuclear Information System (INIS)

    Grunsky, D.; Schroeder, B.

    2008-01-01

    Monitoring of the electrical resistance of the Ta catalyst during the hot wire chemical vapor deposition (HWCVD) of thin silicon films gives information about filament condition. Using Ta filaments for silane decomposition not only the well known strong changes at the cold ends, but also changes of the central part of the filament were observed. Three different phenomena can be distinguished: silicide (stoichiometric Ta X Si Y alloys) growth on the filament surfaces, diffusion of Si into the Ta filament and thick silicon deposits (TSD) formation on the filament surface. The formation of different tantalum silicides on the surface as well as the in-diffusion of silicon increase the filament resistance, while the TSDs form additional electrical current channels and that result in a decrease of the filament resistance. Thus, the filament resistance behaviour during ageing is the result of the competition between these two processes

  10. Filamentous hydrous ferric oxide biosignatures in a pipeline carrying acid mine drainage at Iron Mountain Mine, California

    Science.gov (United States)

    Williams, Amy J.; Alpers, Charles N.; Sumner, Dawn Y.; Campbell, Kate M.

    2017-01-01

    A pipeline carrying acidic mine effluent at Iron Mountain, CA, developed Fe(III)-rich precipitate caused by oxidation of Fe(II)aq. The native microbial community in the pipe included filamentous microbes. The pipe scale consisted of microbial filaments, and schwertmannite (ferric oxyhydroxysulfate, FOHS) mineral spheres and filaments. FOHS filaments contained central lumina with diameters similar to those of microbial filaments. FOHS filament geometry, the geochemical environment, and the presence of filamentous microbes suggest that FOHS filaments are mineralized microbial filaments. This formation of textural biosignatures provides the basis for a conceptual model for the development and preservation of biosignatures in other environments.

  11. Evidence regarding the possible role of c-phycoerythrin in ultraviolet-B tolerance in a thermophilic cyanobacterium

    Energy Technology Data Exchange (ETDEWEB)

    Wingard, C.E.; Castenholz, R.W. [Oregon Univ., Eugene, OR (United States). Dept. of Biology; Schiller, J.R. [Bowdoin College, Brunswick, ME (United States)

    1997-05-01

    It was recently reported that a strain of Nostoc spongiaeforme (cyanobacteria) with the photopigment c-phycoerythrin (c-PE) may be more tolerant of the adverse effects of UVB radiation than the same strain lacking c-PE due to chromatic adaptation (CA) (Tyagi et al., Photochem. Photobiol. 55, 401-407, 1992). It was proposed that this increased UVB tolerance may be due to the presence of c-PE, perhaps as a function of the ability of strains with c-PE to chromatically adapt. We tested the role of c-PE in UVB tolerance by comparing the short- and long-term effects of UVB exposure on photosynthesis pigmentation and the protein contents of four experimental cultures of the thermophilic cyanobacterium Oscillatoria cf. amphigranulata. These cultures consisted of a wild-type strain that produces c-PE, a green pigment variant (subcloned from the parent wild-type strain) incapable of producing c-PE and two chromatically adapted color forms of the wild-type strain that varied with regard to their total c-PE content. There were no significant results suggesting a role for c-PE in UVB tolerance. It is concluded that the photopigment c-PE does not confer enhanced resistance to the deleterious effects of UVB radiation on photosynthesis in this cyanobacterium. (author).

  12. Evidence regarding the possible role of c-phycoerythrin in ultraviolet-B tolerance in a thermophilic cyanobacterium

    International Nuclear Information System (INIS)

    Wingard, C.E.; Castenholz, R.W.

    1997-01-01

    It was recently reported that a strain of Nostoc spongiaeforme (cyanobacteria) with the photopigment c-phycoerythrin (c-PE) may be more tolerant of the adverse effects of UVB radiation than the same strain lacking c-PE due to chromatic adaptation (CA) (Tyagi et al., Photochem. Photobiol. 55, 401-407, 1992). It was proposed that this increased UVB tolerance may be due to the presence of c-PE, perhaps as a function of the ability of strains with c-PE to chromatically adapt. We tested the role of c-PE in UVB tolerance by comparing the short- and long-term effects of UVB exposure on photosynthesis pigmentation and the protein contents of four experimental cultures of the thermophilic cyanobacterium Oscillatoria cf. amphigranulata. These cultures consisted of a wild-type strain that produces c-PE, a green pigment variant (subcloned from the parent wild-type strain) incapable of producing c-PE and two chromatically adapted color forms of the wild-type strain that varied with regard to their total c-PE content. There were no significant results suggesting a role for c-PE in UVB tolerance. It is concluded that the photopigment c-PE does not confer enhanced resistance to the deleterious effects of UVB radiation on photosynthesis in this cyanobacterium. (author)

  13. A Nostoc punctiforme Sugar Transporter Necessary to Establish a Cyanobacterium-Plant Symbiosis1[C][W

    Science.gov (United States)

    Ekman, Martin; Picossi, Silvia; Campbell, Elsie L.; Meeks, John C.; Flores, Enrique

    2013-01-01

    In cyanobacteria-plant symbioses, the symbiotic nitrogen-fixing cyanobacterium has low photosynthetic activity and is supplemented by sugars provided by the plant partner. Which sugars and cyanobacterial sugar uptake mechanism(s) are involved in the symbiosis, however, is unknown. Mutants of the symbiotically competent, facultatively heterotrophic cyanobacterium Nostoc punctiforme were constructed bearing a neomycin resistance gene cassette replacing genes in a putative sugar transport gene cluster. Results of transport activity assays using 14C-labeled fructose and glucose and tests of heterotrophic growth with these sugars enabled the identification of an ATP-binding cassette-type transporter for fructose (Frt), a major facilitator permease for glucose (GlcP), and a porin needed for the optimal uptake of both fructose and glucose. Analysis of green fluorescent protein fluorescence in strains of N. punctiforme bearing frt::gfp fusions showed high expression in vegetative cells and akinetes, variable expression in hormogonia, and no expression in heterocysts. The symbiotic efficiency of N. punctiforme sugar transport mutants was investigated by testing their ability to infect a nonvascular plant partner, the hornwort Anthoceros punctatus. Strains that were specifically unable to transport glucose did not infect the plant. These results imply a role for GlcP in establishing symbiosis under the conditions used in this work. PMID:23463784

  14. Characterization of the coccoid cyanobacterium Myxosarcina sp. KIOST-1 isolated from mangrove forest in Chuuk State, Federated States of Micronesia

    Science.gov (United States)

    Kim, Ji Hyung; Lee, JunMo; Affan, Md-Abu; Lee, Dae-Won; Kang, Do-Hyung

    2017-09-01

    Mangrove forests are known to be inhabited by diverse symbiotic cyanobacterial communities that are capable of N2 fixation. To investigate its biodiversity, root sediments were collected from a mangrove forest in Chuuk State, Federated States of Micronesia (FSM), and an entangled yellow-brown coccoid cyanobacterium was isolated. The isolated cyanobacterium was reproduced by multiple fission and eventually produced baeocytes. Phylogenetic analysis revealed that the isolate was most similar to the genera Myxosarcina and Chroococcidiopsis in the order Pleurocapsales. Compositions of protein, lipid and carbohydrate in the cyanobacterial cells were estimated to be 19.4 ± 0.1%, 18.8 ± 0.4% and 31.5 ± 0.1%, respectively. Interestingly, total fatty acids in the isolate were mainly composed of saturated fatty acids and monounsaturated fatty acids, whereas polyunsaturated fatty acids were not detected. Based on the molecular and biochemical characteristics, the isolate was finally classified in the genus Myxosarcina, and designated as Myxosarcina sp. KIOST-1. These results will contribute to better understanding of cyanobacterial biodiversity in the mangrove forest in FSM as well as the genus Myxosarcina, and also will allow further exploitation of its biotechnological potential on the basis of its cellular characteristics.

  15. Characterization of the cytochrome c oxidase in isolated and purified plasma membranes from the cyanobacterium Anacystis nidulans

    International Nuclear Information System (INIS)

    Peschek, G.A.; Wastyn, M.; Trnka, M.; Molitor, V.; Fry, I.V.; Packer, L.

    1989-01-01

    Functionally intact plasma membranes were isolated from the cyanobacterium (blue-green alga) Anacystis nidulans through French pressure cell extrusion of lysozyme/EDTA-treated cells, separated from thylakoid membranes by discontinuous sucrose density gradient centrifugation, and purified by repeated recentrifugation. Origin and identity of the chlorophyll-free plasma membrane fraction were confirmed by labeling of intact cells with impermeant protein markers, [ 35 S]diazobenzenesulfonate and fluorescamine, prior to membrane isolation. Rates of oxidation of reduced horse heart cytochrome c by purified plasma and thylakoid membranes were 90 and 2 nmol min -1 (mg of protein) -1 , respectively. The cytochrome oxidase in isolated plasma membranes was identified as a copper-containing aa 3 -type enzyme from the properties of its redox-active and EDTA-resistant Cu 2+ ESR signal, the characteristic inhibition profile, reduced minus oxidized difference spectra, carbon monoxide difference spectra, photoaction and photodissociation spectra of the CO-inhibited enzyme, and immunological cross-reaction of two subunits of the enzyme with antibodies against subunits I and II, and the holoenzyme, of Paracoccus denitrificans aa 3 -type cytochrome oxidase. The data presented are the first comprehensive evidence for the occurrence of aa 3 -type cytochrome oxidase in the plasma membrane of a cyanobacterium similar to the corresponding mitochondrial enzyme

  16. Chemical Strategies for the Covalent Modification of Filamentous Phage

    Directory of Open Access Journals (Sweden)

    Matthew B Francis

    2014-12-01

    Full Text Available Historically filamentous bacteriophage have been known to be the workhorse of phage display due to their ability to link genotype to phenotype. More recently, the filamentous phage scaffold has proved to be powerful outside the realms of phage display technology in fields such as molecular imaging, cancer research and materials and vaccine development. The ability of the virion to serve as a platform for a variety of applications heavily relies on the functionalization of the phage coat proteins with a wide variety of functionalities. Genetic modification of the coat proteins has been the most widely used strategy for functionalizing the virion; however complementary chemical modification strategies can help to diversify the range of materials that can be developed. This review emphasizes the recent advances that have been made in the chemical modification of filamentous phage as well as some of the challenges that are involved functionalizing the virion.

  17. The formation and disappearance of filament barbs observed by SDO

    Science.gov (United States)

    Li, Leping; Zhang, Jun

    2014-01-01

    Employing six-day (August 16-21, 2010) SDO/AIA observations, we systematically investigate the formation and disappearance of 58 barbs of a northern (~N60) polar crown filament. Three different ways of barb formation are discovered, including (1) the convergence of surrounding moving materials (55.2%), (2) the flows of materials from the filament (37.9%), and (3) the material injections from neighboring brightening regions (6.9%). We also find three different types of barb disappearance, involving: (i) the bi-lateral movements (44.8%), and (ii) the outflowing (27.6%) of barb material resulting in the barb disappearance, as well as (iii) the barb disappearance associated with neighboring brightenings (27.6%). We propose that barbs exchange materials with the filament, surrounding atmosphere, and nearby brightening regions, causing the barb formation and disappearance.

  18. SOLAR MAGNETIZED 'TORNADOES': RELATION TO FILAMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Su Yang; Veronig, Astrid; Temmer, Manuela [IGAM-Kanzelhoehe Observatory, Institute of Physics, University of Graz, Universitaetsplatz 5, A-8010 Graz (Austria); Wang Tongjiang [Department of Physics, Catholic University of America, Washington, DC 20064 (United States); Gan Weiqun, E-mail: yang.su@uni-graz.at [Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2012-09-10

    Solar magnetized 'tornadoes', a phenomenon discovered in the solar atmosphere, appear as tornado-like structures in the corona but are rooted in the photosphere. Like other solar phenomena, solar tornadoes are a feature of magnetized plasma and therefore differ distinctly from terrestrial tornadoes. Here we report the first analysis of solar 'tornadoes' (two papers which focused on different aspects of solar tornadoes were published in the Astrophysical Journal Letters and Nature, respectively, during the revision of this Letter). A detailed case study of two events indicates that they are rotating vertical magnetic structures probably driven by underlying vortex flows in the photosphere. They usually exist as a group and are related to filaments/prominences, another important solar phenomenon whose formation and eruption are still mysteries. Solar tornadoes may play a distinct role in the supply of mass and twists to filaments. These findings could lead to a new explanation of filament formation and eruption.

  19. Filament structures at the plasma edge on MAST

    International Nuclear Information System (INIS)

    Kirk, A; Ayed, N Ben; Counsell, G; Dudson, B; Eich, T; Herrmann, A; Koch, B; Martin, R; Meakins, A; Saarelma, S; Scannell, R; Tallents, S; Walsh, M; Wilson, H R

    2006-01-01

    The boundary of the tokamak core plasma, or scrape-off layer, is normally characterized in terms of average parameters such as density, temperature and e-folding lengths suggesting diffusive losses. However, as is shown in this paper, localized filamentary structures play an important role in determining the radial efflux in both L mode and during edge localized modes (ELMs) on MAST. Understanding the size, poloidal and toroidal localization and the outward radial extent of these filaments is crucial in order to calculate their effect on power loading both on the first wall and the divertor target plates in future devices. The spatial and temporal evolution of filaments observed on MAST in L-mode and ELMs have been compared and contrasted in order to confront the predictions of various models that have been proposed to predict filament propagation and in particular ELM energy losses

  20. Fast, controlled stepping drive for D2 filament ejection

    International Nuclear Information System (INIS)

    Amenda, W.; Lang, R.S.

    1985-01-01

    Centrifugal pellet injectors are required to refuel plasma machines. The pellet feed into the centrifuge should, if possible, be direct to keep the exit angle divergence small. The D 2 filaments used are first stored in a cryostat and then rapidly transported to the intake region of the centrifuge. An intermittent drive for fast, controlled ejection of D 2 filaments is described here. Mean filament speed of up to 0.6 m/s per step (1.2 mm) are achieved for the centrifugal pellet injector which refuels the ASDEX tokamak at Garching. The timing of the (81) step shifts can be synchronized with the rotor motion. The drive allows rates of up to 50 pellets per second. The drive method also seems to be suitable for direct feeding of other known centrifugal pellet injectors

  1. Vortex Filaments in Grids for Scalable, Fine Smoke Simulation.

    Science.gov (United States)

    Meng, Zhang; Weixin, Si; Yinling, Qian; Hanqiu, Sun; Jing, Qin; Heng, Pheng-Ann

    2015-01-01

    Vortex modeling can produce attractive visual effects of dynamic fluids, which are widely applicable for dynamic media, computer games, special effects, and virtual reality systems. However, it is challenging to effectively simulate intensive and fine detailed fluids such as smoke with fast increasing vortex filaments and smoke particles. The authors propose a novel vortex filaments in grids scheme in which the uniform grids dynamically bridge the vortex filaments and smoke particles for scalable, fine smoke simulation with macroscopic vortex structures. Using the vortex model, their approach supports the trade-off between simulation speed and scale of details. After computing the whole velocity, external control can be easily exerted on the embedded grid to guide the vortex-based smoke motion. The experimental results demonstrate the efficiency of using the proposed scheme for a visually plausible smoke simulation with macroscopic vortex structures.

  2. Controlling Plasma Channels through Ultrashort Laser Pulse Filamentation

    Science.gov (United States)

    Ionin, Andrey; Seleznev, Leonid; Sunchugasheva, Elena

    2013-09-01

    A review of studies fulfilled at the Lebedev Institute in collaboration with the Moscow State University and Institute of Atmospheric Optics in Tomsk on influence of various characteristics of ultrashort laser pulse on plasma channels formed under its filamentation is presented. Filamentation of high-power laser pulses with wavefront controlled by a deformable mirror, with cross-sections spatially formed by various diaphragms and with different wavelengths was experimentally and numerically studied. An application of plasma channels formed due to filamentation of ultrashort laser pulse including a train of such pulses for triggering and guiding long electric discharges is discussed. The research was supported by RFBR Grants 11-02-12061-ofi-m and 11-02-01100, and EOARD Grant 097007 through ISTC Project 4073 P

  3. Structural Basis of Actin Filament Nucleation by Tandem W Domains

    Science.gov (United States)

    Chen, Xiaorui; Ni, Fengyun; Tian, Xia; Kondrashkina, Elena; Wang, Qinghua; Ma, Jianpeng

    2013-01-01

    SUMMARY Spontaneous nucleation of actin is very inefficient in cells. To overcome this barrier, cells have evolved a set of actin filament nucleators to promote rapid nucleation and polymerization in response to specific stimuli. However, the molecular mechanism of actin nucleation remains poorly understood. This is hindered largely by the fact that actin nucleus, once formed, rapidly polymerizes into filament, thus making it impossible to capture stable multisubunit actin nucleus. Here, we report an effective double-mutant strategy to stabilize actin nucleus by preventing further polymerization. Employing this strategy, we solved the crystal structure of AMPPNP-actin in complex with the first two tandem W domains of Cordon-bleu (Cobl), a potent actin filament nucleator. Further sequence comparison and functional studies suggest that the nucleation mechanism of Cobl is probably shared by the p53 cofactor JMY, but not Spire. Moreover, the double-mutant strategy opens the way for atomic mechanistic study of actin nucleation and polymerization. PMID:23727244

  4. On the association of magnetic clouds with disappearing filaments

    International Nuclear Information System (INIS)

    Wilson, R.M.; Hildner, E.

    1986-01-01

    We present evidence that an interplanetary magnetic cloud preceding an interaction region, observed at earth January 24, 1974, is associated with the eruptive filament or disparition brusque (DB) near central meridian on January 18. The DB also was associated with a long-decay soft X ray transient (LDE) and a long-duration gradual-rise-and-fall (GRF) radio burst. To assess whether magnetic clouds are generally associated with DBs, we present results from statistical testing of the relation of 33 magnetic clouds (and 33 control samples without magnetic clouds) to disappearing filaments near central meridian (approx. 99% confidence. There is a suggestion that clouds following shocks, probably launched at times of solar flares, are not as strongly associated with disappearing filaments as are clouds launched less violently

  5. HupW Protease Specifically Required for Processing of the Catalytic Subunit of the Uptake Hydrogenase in the Cyanobacterium Nostoc sp. Strain PCC 7120

    Science.gov (United States)

    Lindberg, Pia; Devine, Ellenor; Stensjö, Karin

    2012-01-01

    The maturation process of [NiFe] hydrogenases includes a proteolytic cleavage of the large subunit. We constructed a mutant of Nostoc strain PCC 7120 in which hupW, encoding a putative hydrogenase-specific protease, is inactivated. Our results indicate that the protein product of hupW selectively cleaves the uptake hydrogenase in this cyanobacterium. PMID:22020512

  6. Concerted changes in gene expression and cell physiology of the cyanobacterium Synechocystis sp. strain PCC 6803 during transitions between nitrogen and light-limited growth

    NARCIS (Netherlands)

    Aquirre von Wobeser, E.; Ibelings, B.W.; Bok, J.M.; Krasikov, V.; Huisman, J.; Matthijs, H.C.P.

    2011-01-01

    Physiological adaptation and genome-wide expression profiles of the cyanobacterium Synechocystis sp. strain PCC 6803 in response to gradual transitions between nitrogen-limited and light-limited growth conditions were measured in continuous cultures. Transitions induced changes in pigment

  7. The Genome Sequence of the Cyanobacterium Oscillatoria sp. PCC 6506 Reveals Several Gene Clusters Responsible for the Biosynthesis of Toxins and Secondary Metabolites▿

    Science.gov (United States)

    Méjean, Annick; Mazmouz, Rabia; Mann, Stéphane; Calteau, Alexandra; Médigue, Claudine; Ploux, Olivier

    2010-01-01

    We report a draft sequence of the genome of Oscillatoria sp. PCC 6506, a cyanobacterium that produces anatoxin-a and homoanatoxin-a, two neurotoxins, and cylindrospermopsin, a cytotoxin. Beside the clusters of genes responsible for the biosynthesis of these toxins, we have found other clusters of genes likely involved in the biosynthesis of not-yet-identified secondary metabolites. PMID:20675499

  8. THE STRUCTURE OF PHOTOSYSTEM-I FROM THE THERMOPHILIC CYANOBACTERIUM SYNECHOCOCCUS SP DETERMINED BY ELECTRON-MICROSCOPY OF 2-DIMENSIONAL CRYSTALS

    NARCIS (Netherlands)

    BOTTCHER, B; GRABER, P; BOEKEMA, EJ

    1992-01-01

    The structure of the Photosystem I (PS I) complex from the thermophilic cyanobacterium Synechococcus sp. has been investigated by electron microscopy and image analysis of two-dimensional crystals. Crystals were obtained from isolated PS I by removal of detergents with Bio-Beads. After negative

  9. Enhancement of human adaptive immune responses by administration of a high-molecular-weight polysaccharide extract from the cyanobacterium Arthrospira platensis

    DEFF Research Database (Denmark)

    Pedersen, Morten Løbner; Walsted, Anette; Larsen, Rune

    2008-01-01

    The effect of consumption of Immulina, a high-molecular-weight polysaccharide extract from the cyanobacterium Arthrospira platensis, on adaptive immune responses was investigated by evaluation of changes in leukocyte responsiveness to two foreign recall antigens, Candida albicans (CA) and tetanus...

  10. Solo and keratin filaments regulate epithelial tubule morphology.

    Science.gov (United States)

    Nishimura, Ryosuke; Kato, Kagayaki; Fujiwara, Sachiko; Ohashi, Kazumasa; Mizuno, Kensaku

    2018-04-28

    Epithelial tubules, consisting of the epithelial cell sheet with a central lumen, are the basic structure of many organs. Mechanical forces play an important role in epithelial tubulogenesis; however, little is known about the mechanisms controlling the mechanical forces during epithelial tubule morphogenesis. Solo (also known as ARHGEF40) is a RhoA-targeting guanine-nucleotide exchange factor that is involved in mechanical force-induced RhoA activation and stress fiber formation. Solo binds to keratin-8/keratin-18 (K8/K18) filaments, and this interaction plays a crucial role in mechanotransduction. In this study, we examined the roles of Solo and K8/K18 filaments in epithelial tubulogenesis using MDCK cells cultured in 3D collagen gels. Knockdown of either Solo or K18 resulted in rounder tubules with increased lumen size, indicating that Solo and K8/K18 filaments play critical roles in forming the elongated morphology of epithelial tubules. Moreover, knockdown of Solo or K18 decreased the level of diphosphorylated myosin light chain (a marker of contractile force) at the luminal and outer surfaces of tubules, suggesting that Solo and K8/K18 filaments are involved in the generation of the myosin II-mediated contractile force during epithelial tubule morphogenesis. In addition, K18 filaments were normally oriented along the long axis of the tubule, but knockdown of Solo perturbed their orientation. These results suggest that Solo plays crucial roles in forming the elongated morphology of epithelial tubules and in regulating myosin II activity and K18 filament organization during epithelial tubule formation.

  11. The versatility of hot-filament activated chemical vapor deposition

    International Nuclear Information System (INIS)

    Schaefer, Lothar; Hoefer, Markus; Kroeger, Roland

    2006-01-01

    In the field of activated chemical vapor deposition (CVD) of polycrystalline diamond films, hot-filament activation (HF-CVD) is widely used for applications where large deposition areas are needed or three-dimensional substrates have to be coated. We have developed processes for the deposition of conductive, boron-doped diamond films as well as for tribological crystalline diamond coatings on deposition areas up to 50 cm x 100 cm. Such multi-filament processes are used to produce diamond electrodes for advanced electrochemical processes or large batches of diamond-coated tools and parts, respectively. These processes demonstrate the high degree of uniformity and reproducibility of hot-filament CVD. The usability of hot-filament CVD for diamond deposition on three-dimensional substrates is well known for CVD diamond shaft tools. We also develop interior diamond coatings for drawing dies, nozzles, and thread guides. Hot-filament CVD also enables the deposition of diamond film modifications with tailored properties. In order to adjust the surface topography to specific applications, we apply processes for smooth, fine-grained or textured diamond films for cutting tools and tribological applications. Rough diamond is employed for grinding applications. Multilayers of fine-grained and coarse-grained diamond have been developed, showing increased shock resistance due to reduced crack propagation. Hot-filament CVD is also used for in situ deposition of carbide coatings and diamond-carbide composites, and the deposition of non-diamond, silicon-based films. These coatings are suitable as diffusion barriers and are also applied for adhesion and stress engineering and for semiconductor applications, respectively

  12. Development and manufacture of ultra-fine NbTi filament wires at ALSTHOM

    International Nuclear Information System (INIS)

    Hoang, G.K.; Laumond, Y.; Sabrie, J.L.; Dubots, P.

    1986-01-01

    Ultra-fine NbTi filament wires have been developed and manufactured by ALSTHOM. It is now possible to produce industrial copper -copper-nickel matrix wires with 0.6 mu m NbTi filaments for use in 50 / 60 Hz machines. Smaller filaments with diameters down to 0.08 mu m have been obtained with 254 100 filament wire samples. Studies are now being carried out on copper matrix conductors to reduce the filament diameter. The first results show that it is possible to obtain submicron filaments even in copper matrix wires

  13. Intermediate Filaments as Organizers of Cellular Space: How They Affect Mitochondrial Structure and Function.

    Science.gov (United States)

    Schwarz, Nicole; Leube, Rudolf E

    2016-07-05

    Intermediate filaments together with actin filaments and microtubules form the cytoskeleton, which is a complex and highly dynamic 3D network. Intermediate filaments are the major mechanical stress protectors but also affect cell growth, differentiation, signal transduction, and migration. Using intermediate filament-mitochondrial crosstalk as a prominent example, this review emphasizes the importance of intermediate filaments as crucial organizers of cytoplasmic space to support these functions. We summarize observations in different mammalian cell types which demonstrate how intermediate filaments influence mitochondrial morphology, subcellular localization, and function through direct and indirect interactions and how perturbations of these interactions may lead to human diseases.

  14. Design of the klystron filament power supply control system for EAST LHCD

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Zege; Wang, Mao; Hu, Huaichuan; Ma, Wendong; Zhou, Taian; Zhou, Faxin; Liu, Fukun; Shan, Jiafang [Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031 (China)

    2016-09-15

    A filament is a critical component of the klystron used to heat the cathode. There are totally 44 klystrons in experimental advanced superconducting tokamak (EAST) lower hybrid current drive (LHCD) systems. All klystron filaments are powered by AC power suppliers through isolated transformers. In order to achieve better klystron preheat, a klystron filament power supply control system is designed to obtain the automatic control of all filament power suppliers. Klystron filament current is measured by PLC and the interlock between filament current and klystron high voltage system is also implemented. This design has already been deployed in two LHCD systems and proves feasible completely.

  15. Fine Structure of a Laser-Plasma Filament in Air

    International Nuclear Information System (INIS)

    Eisenmann, Shmuel; Pukhov, Anatoly; Zigler, Arie

    2007-01-01

    The ability to select and stabilize a single filament during propagation of an ultrashort high-intensity laser pulse in air makes it possible to examine the longitudinal structure of the plasma channel left in its wake. We present detailed measurements of plasma density variations along laser propagation. Over the length of the filament, electron density variations of 3 orders of magnitude are measured. They display evidence of a meter-long postionization range, along which a self-guided structure is observed coupled with a low plasma density, corresponding to ∼3 orders of magnitude decrease from the peak density level

  16. Fine Structure of a Laser-Plasma Filament in Air

    Science.gov (United States)

    Eisenmann, Shmuel; Pukhov, Anatoly; Zigler, Arie

    2007-04-01

    The ability to select and stabilize a single filament during propagation of an ultrashort high-intensity laser pulse in air makes it possible to examine the longitudinal structure of the plasma channel left in its wake. We present detailed measurements of plasma density variations along laser propagation. Over the length of the filament, electron density variations of 3 orders of magnitude are measured. They display evidence of a meter-long postionization range, along which a self-guided structure is observed coupled with a low plasma density, corresponding to ˜3 orders of magnitude decrease from the peak density level.

  17. Strength analysis of filament-wound composite tubes

    Directory of Open Access Journals (Sweden)

    Vasović Ivana

    2010-01-01

    Full Text Available The subject of this work is focused on strength analysis of filament-wound composite tubes made of E glass/polyester under internal pressure. The primary attention of this investigation is to develop a reliable computation procedure for stress, displacement and initial failure analysis of layered composite tubes. For that purpose we have combined the finite element method (FEM with corresponding initial failure criterions. In addition, finite element analyses using commercial code, MSC/NASTRAN, were performed to predict the behavior of filament wound structures. Computation results are compared with experiments. Good agreement between computation and experimental results are obtained.

  18. Whole life cycle of femtosecond ultraviolet filaments in water

    Science.gov (United States)

    Jarnac, Amélie; Tamosauskas, Gintaras; Majus, Donatas; Houard, Aurélien; Mysyrowicz, André; Couairon, Arnaud; Dubietis, Audrius

    2014-03-01

    We present measurements fully characterizing the whole life cycle of femtosecond pulses undergoing filamentation in water at 400 nm. The complete pulse dynamics is monitored by means of a four-dimensional mapping technique for the intensity distribution I (x,y,z,t) during the nonlinear interaction. Measured events (focusing or defocusing cycles, pulse splitting and replenishment, supercontinuum generation, conical emission, nonlinear absorption peaks) are mutually connected.The filament evolution from laser energy deposition in water, which is of paramount importance for a wide range of technological and medical applications, is interpreted in light of simulation results.

  19. Impact of matric potential and pore size distribution on growth dynamics of filamentous and non-filamentous soil bacteria.

    Directory of Open Access Journals (Sweden)

    Alexandra B Wolf

    Full Text Available The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus and a motile rod-shaped bacterium (Bacillus weihenstephanensis to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions. These data, combined with information on bacterial motility (expansion potential across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities.

  20. Impact of matric potential and pore size distribution on growth dynamics of filamentous and non-filamentous soil bacteria.

    Science.gov (United States)

    Wolf, Alexandra B; Vos, Michiel; de Boer, Wietse; Kowalchuk, George A

    2013-01-01

    The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to what extent, filamentous bacteria may also display similar advantages over non-filamentous bacteria in soils with low hydraulic connectivity. In addition to allowing for microbial interactions and competition across connected micro-sites, water films also facilitate the motility of non-filamentous bacteria. To examine these issues, we constructed and characterized a series of quartz sand microcosms differing in matric potential and pore size distribution and, consequently, in connection of micro-habitats via water films. Our sand microcosms were used to examine the individual and competitive responses of a filamentous bacterium (Streptomyces atratus) and a motile rod-shaped bacterium (Bacillus weihenstephanensis) to differences in pore sizes and matric potential. The Bacillus strain had an initial advantage in all sand microcosms, which could be attributed to its faster growth rate. At later stages of the incubation, Streptomyces became dominant in microcosms with low connectivity (coarse pores and dry conditions). These data, combined with information on bacterial motility (expansion potential) across a range of pore-size and moisture conditions, suggest that, like their much larger fungal counterparts, filamentous bacteria also use this growth form to facilitate growth and expansion under conditions of low hydraulic conductivity. The sand microcosm system developed and used in this study allowed for precise manipulation of hydraulic properties and pore size distribution, thereby providing a useful approach for future examinations of how these properties influence the composition, diversity and function of soil-borne microbial communities.

  1. The persistence and ecological impacts of a cyanobacterium genetically engineered to express mosquitocidal Bacillus thuringiensis toxins.

    Science.gov (United States)

    Ketseoglou, Irene; Bouwer, Gustav

    2016-05-10

    The cyanobacterium Anabaena PCC 7120#11 has been genetically engineered to act as a delivery vehicle for Bacillus thuringiensis subspecies israelensis mosquitocidal toxins. To address ecological concerns about releasing this genetically engineered microorganism into the environment for mosquito larva control, the persistence and ecological impacts of PCC 7120#11 was evaluated using multi-species, standardized aquatic microcosms. The microcosms were set up as described in ASTM E1366-02 (Standard Practice for Standardized Aquatic Microcosms: Fresh Water), with a few modifications. The treatment group microcosms were inoculated with PCC 7120#11 and key water quality parameters and non-target effects were compared between the treatment and control groups over a period of 35 days. PCC 7120#11 decreased from a concentration of 4.50 × 10(6) cells/ml (at inoculation) to 1.32 × 10(3) cells/ml after 4 weeks and larvicidal activity against third instar larvae of Anopheles arabiensis was only evident for two weeks after treatment. Both treatment and the interaction of treatment and time had a significant effect on nitrate, phosphate and photosynthetic microorganism concentrations. Treatment with PCC 7120#11 caused a temporary spike in ammonia in the microcosms a week after treatment, but the concentrations were well below acute and chronic criteria values for ammonia in freshwater ecosystems. Cyprinotus vidua concentrations were not significantly different between PCC 7120#11 and control microcosms. In PCC 7120#11 microcosms, Daphnia pulex concentrations were significantly lower than control concentrations between days 18 and 25. By the end of the experiment, none of the measured variables were significantly different between the treatment groups. The standard aquatic microcosm experiments provided more data on the ecological impacts of PCC 7120#11 than single-organism assessments would have. On the basis of the relatively minor, short-term effects that PCC 7120

  2. Solar Tornadoes Triggered by Interaction between Filaments and EUV Jets

    International Nuclear Information System (INIS)

    Chen, Huadong; Zhang, Jun; Ma, Suli; Yan, Xiaoli; Xue, Jianchao

    2017-01-01

    We investigate the formations and evolutions of two successive solar tornadoes in/near AR 12297 during 2015 March 19–20. Recurrent EUV jets close to two filaments were detected along a large-scale coronal loop prior to the appearances of the tornadoes. Under the disturbances from the activities, the filaments continually ascended and finally interacted with the loops tracked by the jets. Subsequently, the structures of the filaments and the loop were merged together, probably via magnetic reconnections, and formed tornado-like structures with a long spiral arm. Our observations suggest that solar tornadoes can be triggered by the interaction between filaments and nearby coronal jets, which has rarely been reported before. At the earlier development phase of the first tornado, about 30 small-scale sub-jets appeared in the tornado’s arm, accompanied by local EUV brightenings. They have an ejection direction approximately vertical to the axis of the arm and a typical maximum speed of ∼280 km s −1 . During the ruinations of the two tornadoes, fast plasma outflows from the strong EUV brightenings inside tornadoes are observed, in company with the untangling or unwinding of the highly twisted tornado structures. These observational features indicate that self reconnections probably occurred between the tangled magnetic fields of the tornadoes and resulted in the rapid disintegrations and disappearances of the tornadoes. According to the reconnection theory, we also derive the field strength of the tornado core to be ∼8 G.

  3. Solar Tornadoes Triggered by Interaction between Filaments and EUV Jets

    Science.gov (United States)

    Chen, Huadong; Zhang, Jun; Ma, Suli; Yan, Xiaoli; Xue, Jianchao

    2017-05-01

    We investigate the formations and evolutions of two successive solar tornadoes in/near AR 12297 during 2015 March 19-20. Recurrent EUV jets close to two filaments were detected along a large-scale coronal loop prior to the appearances of the tornadoes. Under the disturbances from the activities, the filaments continually ascended and finally interacted with the loops tracked by the jets. Subsequently, the structures of the filaments and the loop were merged together, probably via magnetic reconnections, and formed tornado-like structures with a long spiral arm. Our observations suggest that solar tornadoes can be triggered by the interaction between filaments and nearby coronal jets, which has rarely been reported before. At the earlier development phase of the first tornado, about 30 small-scale sub-jets appeared in the tornado’s arm, accompanied by local EUV brightenings. They have an ejection direction approximately vertical to the axis of the arm and a typical maximum speed of ˜280 km s-1. During the ruinations of the two tornadoes, fast plasma outflows from the strong EUV brightenings inside tornadoes are observed, in company with the untangling or unwinding of the highly twisted tornado structures. These observational features indicate that self reconnections probably occurred between the tangled magnetic fields of the tornadoes and resulted in the rapid disintegrations and disappearances of the tornadoes. According to the reconnection theory, we also derive the field strength of the tornado core to be ˜8 G.

  4. Robust authentication through stochastic femtosecond laser filament induced scattering surfaces

    International Nuclear Information System (INIS)

    Zhang, Haisu; Tzortzakis, Stelios

    2016-01-01

    We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.

  5. Solar Tornadoes Triggered by Interaction between Filaments and EUV Jets

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Huadong; Zhang, Jun; Ma, Suli [Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Yan, Xiaoli [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Xue, Jianchao, E-mail: hdchen@nao.cas.cn, E-mail: zjun@nao.cas.cn [Key Laboratory for Dark Matter and Space Science, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)

    2017-05-20

    We investigate the formations and evolutions of two successive solar tornadoes in/near AR 12297 during 2015 March 19–20. Recurrent EUV jets close to two filaments were detected along a large-scale coronal loop prior to the appearances of the tornadoes. Under the disturbances from the activities, the filaments continually ascended and finally interacted with the loops tracked by the jets. Subsequently, the structures of the filaments and the loop were merged together, probably via magnetic reconnections, and formed tornado-like structures with a long spiral arm. Our observations suggest that solar tornadoes can be triggered by the interaction between filaments and nearby coronal jets, which has rarely been reported before. At the earlier development phase of the first tornado, about 30 small-scale sub-jets appeared in the tornado’s arm, accompanied by local EUV brightenings. They have an ejection direction approximately vertical to the axis of the arm and a typical maximum speed of ∼280 km s{sup −1}. During the ruinations of the two tornadoes, fast plasma outflows from the strong EUV brightenings inside tornadoes are observed, in company with the untangling or unwinding of the highly twisted tornado structures. These observational features indicate that self reconnections probably occurred between the tangled magnetic fields of the tornadoes and resulted in the rapid disintegrations and disappearances of the tornadoes. According to the reconnection theory, we also derive the field strength of the tornado core to be ∼8 G.

  6. Small-scale eruptive filaments on the quiet sun

    International Nuclear Information System (INIS)

    Hermans, L.M.; Martin, S.F.

    1986-01-01

    A study of a little known class of eruptive events on the quiet sun was conducted. All of 61 small-scale eruptive filamentary structures were identified in a systematic survey of 32 days of H alpha time-lapse films of the quiet sun acquired at Big Bear Solar Observatory. When fully developed, these structures have an average length of 15 arc seconds before eruption. They appear to be the small-scale analog of large-scale eruptive filaments observed against the disk. At the observed rate of 1.9 small-scale eruptive features per field of view per average 7.0 hour day, the rate of occurence of these events on the sun were estimated to be greater than 600 per 24 hour day.. The average duration of the eruptive phase was 26 minutes while the average lifetime from formation through eruption was 70 minutes. A majority of the small-scale filamentary sturctures were spatially related to cancelling magnetic features in line-of-sight photospheric magnetograms. Similar to large-scale filaments, the small-scale filamentary structures sometimes divided opposite polarity cancelling fragments but often had one or both ends terminating at a cancellation site. Their high numbers appear to reflect the much greater flux on the quiet sun. From their characteristics, evolution, and relationship to photospheric magnetic flux, it was concluded that the structures described are small-scale eruptive filaments and are a subset of all filaments

  7. Automated image analysis for quantification of filamentous bacteria

    DEFF Research Database (Denmark)

    Fredborg, Marlene; Rosenvinge, Flemming Schønning; Spillum, Erik

    2015-01-01

    in systems relying on colorimetry or turbidometry (such as Vitek-2, Phoenix, MicroScan WalkAway). The objective was to examine an automated image analysis algorithm for quantification of filamentous bacteria using the 3D digital microscopy imaging system, oCelloScope. Results Three E. coli strains displaying...

  8. Sensitivity of RF-driven Plasma Filaments to Trace Gases

    Science.gov (United States)

    Burin, M. J.; Czarnocki, C. J.; Czarnocki, K.; Zweben, S. J.; Zwicker, A.

    2011-10-01

    Filamentary structures have been observed in many types of plasma discharges in both natural (e.g. lightning) and industrial systems (e.g. dielectric barrier discharges). Recent progress has been made in characterizing these structures, though various aspects of their essential physics remain unclear. A common example of this phenomenon can be found within a toy plasma globe (or plasma ball), wherein a primarily neon gas mixture near atmospheric pressure clearly and aesthetically displays filamentation. Recent work has provided the first characterization of these plasma globe filaments [Campanell et al., Physics of Plasmas 2010], where it was noticed that discharges of pure gases tend not to produce filaments. We have extended this initial work to investigate in greater detail the dependence of trace gases on filamentation within a primarily Neon discharge. Our preliminary results using a custom globe apparatus will be presented, along with some discussion of voltage dependencies. Newly supported by the NSF/DOE Partnership in Basic Plasma Science and Engineering.

  9. 3D Filament Network Segmentation with Multiple Active Contours

    Science.gov (United States)

    Xu, Ting; Vavylonis, Dimitrios; Huang, Xiaolei

    2014-03-01

    Fluorescence microscopy is frequently used to study two and three dimensional network structures formed by cytoskeletal polymer fibers such as actin filaments and microtubules. While these cytoskeletal structures are often dilute enough to allow imaging of individual filaments or bundles of them, quantitative analysis of these images is challenging. To facilitate quantitative, reproducible and objective analysis of the image data, we developed a semi-automated method to extract actin networks and retrieve their topology in 3D. Our method uses multiple Stretching Open Active Contours (SOACs) that are automatically initialized at image intensity ridges and then evolve along the centerlines of filaments in the network. SOACs can merge, stop at junctions, and reconfigure with others to allow smooth crossing at junctions of filaments. The proposed approach is generally applicable to images of curvilinear networks with low SNR. We demonstrate its potential by extracting the centerlines of synthetic meshwork images, actin networks in 2D TIRF Microscopy images, and 3D actin cable meshworks of live fission yeast cells imaged by spinning disk confocal microscopy.

  10. Alignments of galaxies within cosmic filaments from SDSS DR7

    International Nuclear Information System (INIS)

    Zhang, Youcai; Yang, Xiaohu; Wang, Huiyuan; Wang, Lei; Mo, H. J.; Van den Bosch, Frank C.

    2013-01-01

    Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7, we examine the alignment between the orientation of galaxies and their surrounding large-scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups above a certain mass threshold. We find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets. The strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of dark matter halos in N-body simulations. This suggests that red, central galaxies are well aligned with their host halos, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies. There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals. We also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor. These observational results indicate that galaxy formation is affected by large-scale environments and strongly suggest that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.

  11. The physiology of the filamentous bacterium Microthrix parvicella

    NARCIS (Netherlands)

    Slijkhuis, H.

    1983-01-01

    A study has been made of the physiology of Microthrix parvicella. This filamentous bacterium often causes poor settleability of activated sludge in oxidation ditches supplied with domestic sewage. The organism was found to utilize only long chain fatty acids (preferably in

  12. Alignments of galaxies within cosmic filaments from SDSS DR7

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Youcai; Yang, Xiaohu [Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Nandan Road 80, Shanghai 200030 (China); Wang, Huiyuan [Key Laboratory for Research in Galaxies and Cosmology, University of Science and Technology of China, Hefei, Anhui 230026 (China); Wang, Lei [Purple Mountain Observatory, the Partner Group of MPI für Astronomie, 2 West Beijing Road, Nanjing 210008 (China); Mo, H. J. [Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305 (United States); Van den Bosch, Frank C., E-mail: yczhang@shao.ac.cn, E-mail: xyang@sjtu.edu.cn [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520-8101 (United States)

    2013-12-20

    Using a sample of galaxy groups selected from the Sloan Digital Sky Survey Data Release 7, we examine the alignment between the orientation of galaxies and their surrounding large-scale structure in the context of the cosmic web. The latter is quantified using the large-scale tidal field, reconstructed from the data using galaxy groups above a certain mass threshold. We find that the major axes of galaxies in filaments tend to be preferentially aligned with the directions of the filaments, while galaxies in sheets have their major axes preferentially aligned parallel to the plane of the sheets. The strength of this alignment signal is strongest for red, central galaxies, and in good agreement with that of dark matter halos in N-body simulations. This suggests that red, central galaxies are well aligned with their host halos, in quantitative agreement with previous studies based on the spatial distribution of satellite galaxies. There is a luminosity and mass dependence that brighter and more massive galaxies in filaments and sheets have stronger alignment signals. We also find that the orientation of galaxies is aligned with the eigenvector associated with the smallest eigenvalue of the tidal tensor. These observational results indicate that galaxy formation is affected by large-scale environments and strongly suggest that galaxies are aligned with each other over scales comparable to those of sheets and filaments in the cosmic web.

  13. Spin alignment of dark matter halos in filaments and walls

    NARCIS (Netherlands)

    Aragon-Calvo, Miguel A.; van de Weygaert, Rien; Jones, Bernard J. T.; van der Hulst, J. M.

    2007-01-01

    The MMF technique is used to segment the cosmic web as seen in a cosmological N-body simulation into wall-like and filament-like structures. We find that the spins and shapes of dark matter halos are significantly correlated with each other and with the orientation of their host structures. The

  14. Spin alignment of dark matter haloes in filaments and walls

    NARCIS (Netherlands)

    Aragón-Calvo, M. A.; Weygaert, R. van de; Jones, B. J. T.; Hulst, T. van der

    2006-01-01

    Abstract: The MMF technique is used to segment the cosmic web as seen in a cosmological N-body simulation into wall-like and filament-like structures. We find that the spins and shapes of dark matter haloes are significantly correlated with each other and with the orientation of their host

  15. Robust authentication through stochastic femtosecond laser filament induced scattering surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Haisu [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Heraklion 71110 (Greece); Tzortzakis, Stelios, E-mail: stzortz@iesl.forth.gr [Institute of Electronic Structure and Laser, Foundation for Research and Technology Hellas, Heraklion 71110 (Greece); Materials Science and Technology Department, University of Crete, 71003 Heraklion (Greece); Science Program, Texas A& M University at Qatar, P.O. Box 23874, Doha (Qatar)

    2016-05-23

    We demonstrate a reliable authentication method by femtosecond laser filament induced scattering surfaces. The stochastic nonlinear laser fabrication nature results in unique authentication robust properties. This work provides a simple and viable solution for practical applications in product authentication, while also opens the way for incorporating such elements in transparent media and coupling those in integrated optical circuits.

  16. Organic acid production in Aspergillus niger and other filamentous fungi

    NARCIS (Netherlands)

    Odoni, Dorett I.

    2017-01-01

    The aim of the thesis was to increase the understanding of organic acid production in Aspergillus niger and other filamentous fungi, with the ultimate purpose to improve A. niger as biotechnological production host.

    In Chapter 1, the use of microbial

  17. Mechanical response of melt-spun amorphous filaments

    International Nuclear Information System (INIS)

    Leal, A A; Reifler, F A; Hufenus, R; Mohanty, G; Michler, J

    2014-01-01

    High-speed melt spinning of a cyclo-olefin polymer (COP) and a copolyamide (CoPA) have been performed. Differential scanning calorimetry curves of the resulting monofilaments show that they remain in an amorphous state even after hot drawing. Wide angle x-ray diffraction patterns of undrawn and drawn COP filaments show that although the material remains in an amorphous state, a degree of orientation is induced in the polymer after drawing. The amorphous filaments show an enhanced bending recovery with respect to different semi-crystalline monofilaments commercially available. However, single fiber axial compressive testing indicates that the amorphous filaments exhibit a compressive modulus value which is 50% lower than what is observed for a reference semi-crystalline PET filament. Analysis of the compressive strains applied by the bending recovery test indicates that while the maximum applied strains remain well within the region of elastic deformation of the amorphous materials, the threshold between elastic and plastic deformation is reached for the semi-crystalline materials. (paper)

  18. Transient filament stretching rheometer I: force balance analysis

    DEFF Research Database (Denmark)

    Szabo, Peter

    1997-01-01

    The filament stretching device which is used increasingly as an apparatus for measuring extensional properties of polymeric liquids isanalysed. A force balance that includes the effects of inertia and surface tension is derived.The force balance may be used to correct for the effects of inertia...

  19. Collapsing vortex filaments and the spectrum of quantum turbulence

    Science.gov (United States)

    Andryushchenko, V. A.; Nemirovskii, S. K.

    2017-01-01

    The method of correlation functions and the method of quantum vortex configurations are used to calculate the energy spectrum of a three-dimensional velocity field that is induced by collapsing (immediately before reconnection) vortex filaments. The formulation of this problem is motivated by the idea of modeling classical turbulence by a set of chaotic quantized vortex filaments. Among the various arguments that support the idea of quasi-classical behavior for quantum turbulence, the most persuasive is probably the resulting Kolmogorov energy spectrum resembling E ( k ) ∝ k - 5 / 3 that was obtained in a number of numerical studies. Another goal is associated with an important and intensely studied theme that relates to the role of hydrodynamic collapse in the formation of turbulence spectra. Calculations have demonstrated that vortex filaments create a velocity field at the moment of contact, which has a singularity. This configuration of vortex filaments generates the spectrum E(k), which bears the resemblance to the Kolmogorov law. A possible cause for this observation is discussed, as well as the likely reasons behind any deviations. The obtained results are discussed from the perspective of both classical and quantum turbulence.

  20. Magnetic islands in tokamaks induced by thermal filamentation

    International Nuclear Information System (INIS)

    Dubois, M.A.; Mohamed-Benkadda, M.S.

    1991-11-01

    The thermal instability of filamentation is revisited in the fully nonlinear regime of a system of cool magnetic island chains, taking into account: the different transport processes inside and outside island cores, and a realistic temperature dependence of radiative losses. This mechanism is found to be a plausible candidate to explain the anomalous electron energy transport

  1. Filament identification and dominance of Eikelboom Type 0092 in ...

    African Journals Online (AJOL)

    In order of prevalence, the five most common dominant filament species in 96 activated sludge samples were: Eikelboom Type 0092, Eikelboom Type 1851, nocardioforms, Microthrix parvicella and Eikelboom Type 021N. In order to compile a statistically significant database, it is recommended that an extensive nationwide ...

  2. The cell wall of the filamentous fungus Aspergillus niger

    NARCIS (Netherlands)

    Damveld, Robbert A.

    2005-01-01

    Fungi are a very successful species and are distributed worldwide. However, the presence of fungi is not always desired. Filamentous fungi can grow on living or dead organic material and even inside the host. Current methods to prevent fungal growth are insufficient, causing fatality after fungal

  3. Analysis of filament statistics in fast camera data on MAST

    Science.gov (United States)

    Farley, Tom; Militello, Fulvio; Walkden, Nick; Harrison, James; Silburn, Scott; Bradley, James

    2017-10-01

    Coherent filamentary structures have been shown to play a dominant role in turbulent cross-field particle transport [D'Ippolito 2011]. An improved understanding of filaments is vital in order to control scrape off layer (SOL) density profiles and thus control first wall erosion, impurity flushing and coupling of radio frequency heating in future devices. The Elzar code [T. Farley, 2017 in prep.] is applied to MAST data. The code uses information about the magnetic equilibrium to calculate the intensity of light emission along field lines as seen in the camera images, as a function of the field lines' radial and toroidal locations at the mid-plane. In this way a `pseudo-inversion' of the intensity profiles in the camera images is achieved from which filaments can be identified and measured. In this work, a statistical analysis of the intensity fluctuations along field lines in the camera field of view is performed using techniques similar to those typically applied in standard Langmuir probe analyses. These filament statistics are interpreted in terms of the theoretical ergodic framework presented by F. Militello & J.T. Omotani, 2016, in order to better understand how time averaged filament dynamics produce the more familiar SOL density profiles. This work has received funding from the RCUK Energy programme (Grant Number EP/P012450/1), from Euratom (Grant Agreement No. 633053) and from the EUROfusion consortium.

  4. Formation of solar filaments by steady and nonsteady chromospheric heating

    NARCIS (Netherlands)

    Xia, C.; Chen, P. F.; Keppens, R.; van Marle, A. J.

    2011-01-01

    It has been established that cold plasma condensations can form in a magnetic loop subject to localized heating of its footpoints. In this paper, we use grid-adaptive numerical simulations of the radiative hydrodynamic equations to investigate the filament formation process in a pre-shaped loop with

  5. Formation of Solar Filaments by Steady and Nonsteady Chromospheric Heating

    NARCIS (Netherlands)

    Xia, C.; Chen, P.F.; Keppens, R.; van Marle, A. -J

    2011-01-01

    It has been established that cold plasma condensations can form in a magnetic loop subject to localized heating of its footpoints. In this paper, we use grid-adaptive numerical simulations of the radiative hydrodynamic equations to investigate the filament formation process in a pre-shaped loop with

  6. Wettability dynamics of liquid filaments on horizontal substrates

    Science.gov (United States)

    Diez, Javier; Ravazzoli, Pablo; Cuellar, Ingrith; Gonzalez, Alejandro

    2017-11-01

    We study the hydrodynamic mechanisms involved in the motion of the contact line formed at the end region of a liquid filament laying on a planar and horizontal substrate. Since the flow develops under partially wetting conditions, the tip of the filament recedes and forms a bulged region (head) that subsequently develops a neck region behind it. Later the neck breaks up leading to a separated drop, while the rest of the filament restarts the sequence. One main feature of this flow is that the whole dynamics and final drop shapes are strongly influenced by the hysteresis of the contact angle typical in most of the liquid-substrate systems. The time evolution till breakup is studied experimentally and pictured in terms of a hybrid wettability theory which involves the Cox-Voinov hydrodynamic approach combined with the molecular kinetic theory developed by Blake. The parameters of this theory are determined for our liquid-substrate system (silicone oil ``coated glass). The experimental results of the retracting filament are described in terms of a simple heuristic model and compared with numerical simulations of the full Navier-Stokes equations. This study is of special interest in the context of pulsed laser-induced dewetting. The authors acknowledge support from Consejo Nacional de Investigaciones Cientficas y Tcnicas (CONICET, Argentina) with Grant PIP 844/2012 and Agencia Nacional de Promocin Cientfica y Tecnolgica (ANPCyT, Argentina) with Grant PICT 931/2012.

  7. Decidable and undecidable arithmetic functions in actin filament networks

    Science.gov (United States)

    Schumann, Andrew

    2018-01-01

    The plasmodium of Physarum polycephalum is very sensitive to its environment, and reacts to stimuli with appropriate motions. Both the sensory and motor stages of these reactions are explained by hydrodynamic processes, based on fluid dynamics, with the participation of actin filament networks. This paper is devoted to actin filament networks as a computational medium. The point is that actin filaments, with contributions from many other proteins like myosin, are sensitive to extracellular stimuli (attractants as well as repellents), and appear and disappear at different places in the cell to change aspects of the cell structure—e.g. its shape. By assembling and disassembling actin filaments, some unicellular organisms, like Amoeba proteus, can move in response to various stimuli. As a result, these organisms can be considered a simple reversible logic gate—extracellular signals being its inputs and motions its outputs. In this way, we can implement various logic gates on amoeboid behaviours. These networks can embody arithmetic functions within p-adic valued logic. Furthermore, within these networks we can define the so-called diagonalization for deducing undecidable arithmetic functions.

  8. Tesla coil discharges guided by femtosecond laser filaments in air

    Science.gov (United States)

    Brelet, Yohann; Houard, Aurélien; Arantchouk, Leonid; Forestier, Benjamin; Liu, Yi; Prade, Bernard; Carbonnel, Jérôme; André, Yves-Bernard; Mysyrowicz, André

    2012-04-01

    A Tesla coil generator was designed to produce high voltage pulses oscillating at 100 kHz synchronisable with a nanosecond temporal jitter. Using this compact high voltage generator, we demonstrate reproducible meter long discharges in air at a repetition rate of 1 Hz. Triggering and guiding of the discharges are performed in air by femtosecond laser filaments.

  9. Nonlinear Bloch waves in metallic photonic band-gap filaments

    International Nuclear Information System (INIS)

    Kaso, Artan; John, Sajeev

    2007-01-01

    We demonstrate the occurrence of nonlinear Bloch waves in metallic photonic crystals (PCs). These periodically structured filaments are characterized by an isolated optical pass band below an effective plasma gap. The pass band occurs in a frequency range where the metallic filament exhibits a negative, frequency-dependent dielectric function and absorption loss. The metallic losses are counterbalanced by gain in two models of inhomogeneously broadened nonlinear oscillators. In the first model, we consider close-packed quantum dots that fill the void regions of a two-dimensional (2D) metallic PC, and whose inhomogeneously broadened emission spectrum spans the original optical pass band of the bare filament. In the second model, we consider thin (10-50 nm) layers of inhomogeneously broadened two-level resonators, with large dipole oscillator strength, that cover the interior surfaces of 2D metallic (silver and tungsten) PCs. These may arise from localized surface plasmon resonances due to small metal particles or an otherwise rough metal surface. For simplicity, we treat electromagnetic modes with electric field perpendicular to the plane of metal periodicity. In both models, a pumping threshold of the resonators is found, above which periodic nonlinear solutions of Maxwell's equations with purely real frequency within the optical pass band emerge. These nonlinear Bloch waves exhibit a laserlike input pumping to output amplitude characteristic. For strong surface resonances, these nonlinear waves may play a role in light emission from a hot tungsten (suitably microstructured) filament

  10. Nonlinear Bloch waves in metallic photonic band-gap filaments

    Science.gov (United States)

    Kaso, Artan; John, Sajeev

    2007-11-01

    We demonstrate the occurrence of nonlinear Bloch waves in metallic photonic crystals (PCs). These periodically structured filaments are characterized by an isolated optical pass band below an effective plasma gap. The pass band occurs in a frequency range where the metallic filament exhibits a negative, frequency-dependent dielectric function and absorption loss. The metallic losses are counterbalanced by gain in two models of inhomogeneously broadened nonlinear oscillators. In the first model, we consider close-packed quantum dots that fill the void regions of a two-dimensional (2D) metallic PC, and whose inhomogeneously broadened emission spectrum spans the original optical pass band of the bare filament. In the second model, we consider thin (10 50 nm) layers of inhomogeneously broadened two-level resonators, with large dipole oscillator strength, that cover the interior surfaces of 2D metallic (silver and tungsten) PCs. These may arise from localized surface plasmon resonances due to small metal particles or an otherwise rough metal surface. For simplicity, we treat electromagnetic modes with electric field perpendicular to the plane of metal periodicity. In both models, a pumping threshold of the resonators is found, above which periodic nonlinear solutions of Maxwell’s equations with purely real frequency within the optical pass band emerge. These nonlinear Bloch waves exhibit a laserlike input pumping to output amplitude characteristic. For strong surface resonances, these nonlinear waves may play a role in light emission from a hot tungsten (suitably microstructured) filament.

  11. Filamentation of ultrashort laser pulses of different wavelengths in ...

    Indian Academy of Sciences (India)

    2017-01-17

    Jan 17, 2017 ... and alluring application prospects of filament are dis- covered, e.g. control of a ... (1) are the linear effects, accounting for the spatial diffraction and the ... The input electric field envelope is modelled by a. Gaussian profile with ...

  12. Bundling Actin Filaments From Membranes: Some Novel Players

    Directory of Open Access Journals (Sweden)

    Clément eThomas

    2012-08-01

    Full Text Available Progress in live-cell imaging of the cytoskeleton has significantly extended our knowledge about the organization and dynamics of actin filaments near the plasma membrane of plant cells. Noticeably, two populations of filamentous structures can be distinguished. On the one hand, fine actin filaments which exhibit an extremely dynamic behavior basically characterized by fast polymerization and prolific severing events, a process referred to as actin stochastic dynamics. On the other hand, thick actin bundles which are composed of several filaments and which are comparatively more stable although they constantly remodel as well. There is evidence that the actin cytoskeleton plays critical roles in trafficking and signaling at both the cell cortex and organelle periphery but the exact contribution of actin bundles remains unclear. A common view is that actin bundles provide the long-distance tracks used by myosin motors to deliver their cargo to growing regions and accordingly play a particularly important role in cell polarization. However, several studies support that actin bundles are more than simple passive highways and display multiple and dynamic roles in the regulation of many processes, such as cell elongation, polar auxin transport, stomatal and chloroplast movement, and defense against pathogens. The list of identified plant actin-bundling proteins is ever expanding, supporting that plant cells shape structurally and functionally different actin bundles. Here I review the most recently characterized actin-bundling proteins, with a particular focus on those potentially relevant to membrane trafficking and/or signaling.

  13. Stochastic calculus of protein filament formation under spatial confinement

    Science.gov (United States)

    Michaels, Thomas C. T.; Dear, Alexander J.; Knowles, Tuomas P. J.

    2018-05-01

    The growth of filamentous aggregates from precursor proteins is a process of central importance to both normal and aberrant biology, for instance as the driver of devastating human disorders such as Alzheimer's and Parkinson's diseases. The conventional theoretical framework for describing this class of phenomena in bulk is based upon the mean-field limit of the law of mass action, which implicitly assumes deterministic dynamics. However, protein filament formation processes under spatial confinement, such as in microdroplets or in the cellular environment, show intrinsic variability due to the molecular noise associated with small-volume effects. To account for this effect, in this paper we introduce a stochastic differential equation approach for investigating protein filament formation processes under spatial confinement. Using this framework, we study the statistical properties of stochastic aggregation curves, as well as the distribution of reaction lag-times. Moreover, we establish the gradual breakdown of the correlation between lag-time and normalized growth rate under spatial confinement. Our results establish the key role of spatial confinement in determining the onset of stochasticity in protein filament formation and offer a formalism for studying protein aggregation kinetics in small volumes in terms of the kinetic parameters describing the aggregation dynamics in bulk.

  14. Evaluation of filamentous green algae as feedstocks for biofuel production.

    Science.gov (United States)

    Zhang, Wei; Zhao, Yonggang; Cui, Binjie; Wang, Hui; Liu, Tianzhong

    2016-11-01

    Compared with unicellular microalgae, filamentous algae have high resistance to grazer-predation and low-cost recovery in large-scale production. Green algae, as the most diverse group of algae, included numerous filamentous genera and species. In this study, records of filamentous genera and species in green algae were firstly censused and classified. Then, seven filamentous strains subordinated in different genera were cultivated in bubbled-column to investigate their growth rate and energy molecular (lipid and starch) capacity. Four strains including Stigeoclonium sp., Oedogonium nodulosum, Hormidium sp. and Zygnema extenue were screened out due to their robust growth. And they all could accumulate triacylglycerols and starch in their biomass, but with different capacity. After nitrogen starvation, Hormidium sp. and Oedogonium nodulosum respectively exhibited high capacity of lipid (45.38% in dry weight) and starch (46.19% in dry weight) accumulation, which could be of high potential as feedstocks for biodiesel and bioethanol production. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. Electron emission regulator for an x-ray tube filament

    International Nuclear Information System (INIS)

    Daniels, H.E.; Randall, H.G.

    1982-01-01

    An x-ray tube ma regulator has an scr phase shift voltage regulator supplying the primary winding of a transformer whose secondary is coupled to the x-ray tube filament. Prior to initiation of an x-ray exposure, the filament is preheated to a temperature corresponding substantially to the electron emissivity needed for obtaining the desired tube ma during an exposure. During the preexposure interval, the phase shift regulator is controlled by a signal corresponding to the sum of signals representative of the voltage applied to the filament transformer, the desired filament voltage and the space charge compensation needed for the selected x-ray tube anode to cathode voltage. When an exposure is initiated, control of the voltage regulator is switched to a circuit that responds to the tube current by controlling the amount of phase shift and, hence, the voltage supplied to the transformer. Transformer leakage current compensation is provided during the exposure interval with a circuit that includes an element whose impedance is varied in accordance with the anode-to-cathode voltage setting so the element drains off tube current as required to cancel the effect of leakage current variations

  16. On filament structure and propagation within a commercial plasma globe

    International Nuclear Information System (INIS)

    Burin, M. J.; Simmons, G. G.; Ceja, H. G.; Zweben, S. J.; Nagy, A.; Brunkhorst, C.

    2015-01-01

    The filamentary discharge seen within commercial plasma globes is commonly enjoyed yet not well understood. Here, we investigate the discharge properties of a plasma globe using a variable high voltage amplifier. We find that increasing voltage magnitude increases the number of filaments while leaving their individual structure basically unchanged, a result typical of dielectric barrier discharges. The frequency of the voltage also affects filament population but more significantly changes filament structure, with more diffuse filaments seen at lower frequencies. Voltage polarity is observed to be important, especially at lower frequencies, where for negative-gradient voltages the discharge is more diffuse, not filamentary. At late stages of the discharge circular structures appear and expand on the glass boundaries. We find no trend of discharge speed with respect to voltage variables, though this may be due to manufacturer sample-to-sample variation. Each voltage cycle the discharge expands outward at ∼10–15 km/s, a speed significantly higher than the estimated electron drift yet considerably lower than that observed for most streamers. We discuss the physics of these observations and their relation to similar discharges that can be found within nature and industry

  17. Filamentation of diamond nanoparticles treated in underwater corona discharge

    Czech Academy of Sciences Publication Activity Database

    Jirásek, Vít; Lukeš, Petr; Kozak, Halyna; Artemenko, Anna; Člupek, Martin; Čermák, Jan; Rezek, Bohuslav; Kromka, Alexander

    2016-01-01

    Roč. 6, č. 3 (2016), 2352-2360 ISSN 2046-2069 R&D Projects: GA ČR GA15-01687S; GA MŠk(CZ) LD14011 Institutional support: RVO:68378271 ; RVO:61389021 Keywords : nanodiamonds * pulsed streamer corona discharge * filamentation Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.108, year: 2016

  18. Influence of plasma background including neutrals on scrape-off layer filaments using 3D simulations

    Directory of Open Access Journals (Sweden)

    D. Schwörer

    2017-08-01

    Full Text Available This paper investigates the effect of the plasma background, including neutrals in a self-consistent way, on filaments in the scrape-off layer (SOL of fusion devices. A strong dependency of filament motion on background density and temperature is observed. The radial filament motion shows an increase in velocity with decreasing background density and increasing background temperature. In the simulations presented here, three neutral-filament interaction models have been compared, one with a static neutral background, one with no interaction between filaments and neutrals, and one co-evolving the neutrals self consistently with the filaments. With the background conditions employed here, which do not show detachment, there are no significant effects of neutrals on filaments, as by the time the filament reaches maximum velocity, the neutral density has not changed significantly.

  19. Filament to filament bridging and its influence on developing high critical current density in multifilamentary Bi2Sr2CaCu2Ox round wires

    International Nuclear Information System (INIS)

    Shen, T; Jiang, J; Kametani, F; Trociewitz, U P; Larbalestier, D C; Schwartz, J; Hellstrom, E E

    2010-01-01

    Increasing the critical current density (J c ) of the multifilamentary round wire Ag/Bi 2 Sr 2 CaCu 2 O x (2212) requires understanding its complicated microstructure, in which extensive bridges between filaments are prominent. In this first through-process quench study of 2212 round wire, we determined how its microstructure develops during a standard partial-melt process and how filament bridging occurs. We found that filaments can bond together in the melt state. As 2212 starts to grow on subsequent cooling, we observed that two types of 2212 bridges form. One type, which we call Type-A bridges, forms within filaments that bonded in the melt; Type-A bridges are single grains that span multiple bonded filaments. The other type, called Type-B bridges, form between discrete filaments through 2212 outgrowths that penetrate into the Ag matrix and intersect with other 2212 outgrowths from adjacent filaments. We believe the ability of these two types of bridges to carry inter-filament current is intrinsically different: Type-A bridges are high- J c inter-filament paths whereas Type-B bridges contain high-angle grain boundaries and are typically weak linked. Slow cooling leads to more filament bonding, more Type-A bridges and a doubling of J c without changing the flux pinning. We suggest that Type-A bridges create a 3D current flow that is vital to developing high J c in multifilamentary 2212 round wire.

  20. Developments in hot-filament metal oxide deposition (HFMOD)

    Energy Technology Data Exchange (ETDEWEB)

    Durrant, Steven F. [Laboratorio de Plasmas Tecnologicos, Campus Experimental de Sorocaba, Universidade Estadual Paulista (UNESP), Avenida Tres de Marco, 511, Alto de Boa Vista, 18087-180 Sorocaba, SP (Brazil)], E-mail: steve@sorocaba.unesp.br; Trasferetti, Benedito C. [Departamento de Policia Federal, Superintendencia Regional no Piaui, Setor Tecnico-Cientifico, Avenida Maranhao, 1022/N, 64.000-010, Teresina, PI (Brazil); Scarminio, Jair [Departamento de Fisica, Universidade Estadual de Londrina (UEL), 86051-990, Londrina, PR (Brazil); Davanzo, Celso U. [Instituto de Quimica, Universidade Estadual de Campinas (UNICAMP), 13083-970, Campinas, SP (Brazil); Rouxinol, Francisco P.M.; Gelamo, Rogerio V.; Bica de Moraes, Mario A. [Laboratorio de Processos de Plasma, Departamento de Fisica Aplicada, Instituto de Fisica Gleb Wataghin, Universidade Estadual de Campinas (UNICAMP), 13083-970, Campinas, SP (Brazil)

    2008-01-15

    Hot-filament metal oxide deposition (HFMOD) is a variant of conventional hot-filament chemical vapor deposition (HFCVD) recently developed in our laboratory and successfully used to obtain high-quality, uniform films of MO{sub x}, WO{sub x} and VO{sub x}. The method employs the controlled oxidation of a filament of a transition metal heated to 1000 deg. C or more in a rarefied oxygen atmosphere (typically, of about 1 Pa). Metal oxide vapor formed on the surface of the filament is transported a few centimetres to deposit on a suitable substrate. Key system parameters include the choice of filament material and diameter, the applied current and the partial pressures of oxygen in the chamber. Relatively high film deposition rates, such as 31 nm min{sup -1} for MoO{sub x}, are obtained. The film stoichiometry depends on the exact deposition conditions. MoO{sub x} films, for example, present a mixture of MoO{sub 2} and MoO{sub 3} phases, as revealed by XPS. As determined by Li{sup +} intercalation using an electrochemical cell, these films also show a colouration efficiency of 19.5 cm{sup 2} C{sup -1} at a wavelength of 700 nm. MO{sub x} and WO{sub x} films are promising in applications involving electrochromism and characteristics of their colouring/bleaching cycles are presented. The chemical composition and structure of VO{sub x} films examined using IRRAS (infrared reflection-absorption spectroscopy), RBS (Rutherford backscattering spectrometry) and XPS (X-ray photoelectron spectrometry) are also presented.

  1. Filament structure, organization, and dynamics in MreB sheets.

    Science.gov (United States)

    Popp, David; Narita, Akihiro; Maeda, Kayo; Fujisawa, Tetsuro; Ghoshdastider, Umesh; Iwasa, Mitsusada; Maéda, Yuichiro; Robinson, Robert C

    2010-05-21

    In vivo fluorescence microscopy studies of bacterial cells have shown that the bacterial shape-determining protein and actin homolog, MreB, forms cable-like structures that spiral around the periphery of the cell. The molecular structure of these cables has yet to be established. Here we show by electron microscopy that Thermatoga maritime MreB forms complex, several mum long multilayered sheets consisting of diagonally interwoven filaments in the presence of either ATP or GTP. This architecture, in agreement with recent rheological measurements on MreB cables, may have superior mechanical properties and could be an important feature for maintaining bacterial cell shape. MreB polymers within the sheets appear to be single-stranded helical filaments rather than the linear protofilaments found in the MreB crystal structure. Sheet assembly occurs over a wide range of pH, ionic strength, and temperature. Polymerization kinetics are consistent with a cooperative assembly mechanism requiring only two steps: monomer activation followed by elongation. Steady-state TIRF microscopy studies of MreB suggest filament treadmilling while high pressure small angle x-ray scattering measurements indicate that the stability of MreB polymers is similar to that of F-actin filaments. In the presence of ADP or GDP, long, thin cables formed in which MreB was arranged in parallel as linear protofilaments. This suggests that the bacterial cell may exploit various nucleotides to generate different filament structures within cables for specific MreB-based functions.

  2. Response of the unicellular diazotrophic cyanobacterium Crocosphaera watsonii to iron limitation.

    Directory of Open Access Journals (Sweden)

    Violaine Jacq

    Full Text Available Iron (Fe is widely suspected as a key controlling factor of N2 fixation due to the high Fe content of nitrogenase and photosynthetic enzymes complex, and to its low concentrations in oceanic surface seawaters. The influence of Fe limitation on the recently discovered unicellular diazotrophic cyanobacteria (UCYN is poorly understood despite their biogeochemical importance in the carbon and nitrogen cycles. To address this knowledge gap, we conducted culture experiments on Crocosphaera watsonii WH8501 growing under a range of dissolved Fe concentrations (from 3.3 to 403 nM. Overall, severe Fe limitation led to significant decreases in growth rate (2.6-fold, C, N and chlorophyll a contents per cell (up to 4.1-fold, N2 and CO2 fixation rates per cell (17- and 7-fold as well as biovolume (2.2-fold. We highlighted a two phased response depending on the degree of limitation: (i under a moderate Fe limitation, the biovolume of C. watsonii was strongly reduced, allowing the cells to keep sufficient energy to maintain an optimal growth, volume-normalized contents and N2 and CO2 fixation rates; (ii with increasing Fe deprivation, biovolume remained unchanged but the entire cell metabolism was affected, as shown by a strong decrease in the growth rate, volume-normalized contents and N2 and CO2 fixation rates. The half-saturation constant for growth of C. watsonii with respect to Fe is twice as low as that of the filamentous Trichodesmium indicating a better adaptation of C. watsonii to poor Fe environments than filamentous diazotrophs. The physiological response of C. watsonii to Fe limitation was different from that previously shown on the UCYN Cyanothece sp, suggesting potential differences in Fe requirements and/or Fe acquisition within the UCYN community. These results contribute to a better understanding of how Fe bioavailability can control the activity of UCYN and explain the biogeography of diverse N2 fixers in ocean.

  3. Enhancement of peak intensity in a filament core with spatiotemporally focused femtosecond laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Bin; Chu Wei; Li Guihua; Zhang Haisu; Ni Jielei [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Graduate School of Chinese Academy of Sciences, Beijing 100080 (China); Gao Hui; Liu Weiwei [Institute of Modern Optics, Nankai University, Tianjin, 300071 (China); Yao Jinping; Cheng Ya; Xu Zhizhan [State Key Laboratory of High Field Laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Chin, See Leang [Center for Optics, Photonics and Laser (COPL) and Department of Physics, Engineering Physics and Optics, Universite Laval, Quebec City, QC, G1V 0A6 (Canada)

    2011-12-15

    We demonstrate that the peak intensity in the filament core, which is inherently limited by the intensity clamping effect during femtosecond laser filamentation, can be significantly enhanced using spatiotemporally focused femtosecond laser pulses. In addition, the filament length obtained by spatiotemporally focused femtosecond laser pulses is {approx}25 times shorter than that obtained by a conventional focusing scheme, resulting in improved high spatial resolution.

  4. Fossil evidence for spin alignment of Sloan Digital Sky Survey galaxies in filaments

    NARCIS (Netherlands)

    Jones, Bernard J. T.; van de Weijgaert, Marinus; Aragon-Calvo, Miguel A.

    2010-01-01

    We search for and find fossil evidence that the spin axes of galaxies in cosmic web filaments relative to their host filaments are not randomly distributed. This indicates the fact that the action of large-scale tidal torques affected the alignments of galaxies located in cosmic filaments. To this

  5. Impact of Matric Potential and Pore Size Distribution on Growth Dynamics of Filamentous and Non-Filamentous Soil Bacteria

    NARCIS (Netherlands)

    Wolf, A.B.; Vos, de M.; Boer, de W.; Kowalchuk, G.A.

    2013-01-01

    The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to

  6. Impact of matric potential and pore size distribution on growth dynamics of filamentous and non-filamentous soil bacteria

    NARCIS (Netherlands)

    Wolf, A.B.; Vos, M.; De Boer, W.; Kowalchuk, G.A.

    2013-01-01

    The filamentous growth form is an important strategy for soil microbes to bridge air-filled pores in unsaturated soils. In particular, fungi perform better than bacteria in soils during drought, a property that has been ascribed to the hyphal growth form of fungi. However, it is unknown if, and to

  7. Photosynthetic and Behavioral Versatility of the Cyanobacterium Oscillatoria-Boryana in a Sulfide-Rich Microbial Mat

    DEFF Research Database (Denmark)

    CASTENHOLZ, RW; JØRGENSEN, BB; DAMELIO, E.

    1991-01-01

    resulted in a downward retreat. The result was a lowered irradiance level for the Oscillatoria but, nevertheless, a high rate of oxygenic photosynthesis. O. boryana is a versatile cyanobacterium that appears to avoid photoinhibitory conditions and to optimize its light intensity for photosynthesis...... with dense O. boryana populations were used to make vertical profiles at intervals of 0.1-0.2 mm and also to estimate rates of oxygenic and anoxygenic photosynthesis during rapid light-dark transitions. In addition, attenuation of irradiance was measured in mats with O. boryana by a spectroradiometer...... with mini-fiber optic probe. Light-dependent incorporation of [C-14]-bicarbonate and [C-14]-acetate was measured in collected field populations of O. boryana. The combined results led to the conclusion that populations of O. boryana typically employed sulfide-dependent anoxygenic photosynthesis in early...

  8. Photoreactivation and excision repair of UV induced pyrimidine dimers in the unicellular cyanobacterium Gloeocapsa alpicola (Synechocystis PCC 6308)

    International Nuclear Information System (INIS)

    O'Brien, P.A.; Houghton, J.A.

    1982-01-01

    The survival curve obtained after UV irradiation of the unicellular cyanobacterium Synechocystis is typical of a DNA repair competent organism. Inhibition of DNA replication, by incubating cells in the dark, increased resistance to the lethal effects of UV at higher fluences. Exposure of irradiated cells to near ultraviolet light (350-500 nm) restored viability to pre-irradiation levels. In order to measure DNA repair activity, techniques have been developed for the chromatographic analysis of pyrimidine dimers in synechocystis. The specificity of this method was established using a haploid strain of Saccharomyces cerevisiae. In accordance with the physiological responses of irradiated cells to photoreactivating light, pyrimidine dimers were not detected after photoreactivation treatment. Incubation of irradiated cells under non-photoreactivating growth conditions for 15h resulted in complete removal of pyrimidine dimers. It is concluded that Synechocystis contains photoreactivation and excision repair systems for the removal of pyrimidine dimers. (author)

  9. Phosphorus addition reverses the positive effect of zebra mussels (Dreissena polymorpha) on the toxic cyanobacterium, Microcystis aeruginosa.

    Science.gov (United States)

    Sarnelle, Orlando; White, Jeffrey D; Horst, Geoffrey P; Hamilton, Stephen K

    2012-07-01

    We tested the hypothesis that zebra mussels (Dreissena polymorpha) have positive effects on the toxin-producing cyanobacterium, Microcystis aeruginosa, at low phosphorus (P) concentrations, but negative effects on M. aeruginosa at high P, with a large-scale enclosure experiment in an oligotrophic lake. After three weeks, mussels had a significantly positive effect on M. aeruginosa at ambient P (total phosphorus, TP ∼10 μg L⁻¹), and a significantly negative effect at high P (simulating a TP of ∼40 μg L⁻¹ in lakes). Positive and negative effects were strong and very similar in magnitude. Thus, we were able to ameliorate a negative effect of Dreissena invasion on water quality (i.e., promotion of Microcystis) by adding P to water from an oligotrophic lake. Our results are congruent with many field observations of Microcystis response to Dreissena invasion across ecosystems of varying P availability. Copyright © 2012 Elsevier Ltd. All rights reserved.

  10. Photosystem Trap Energies and Spectrally-Dependent Energy-Storage Efficiencies in the Chl d-Utilizing Cyanobacterium, Acaryochloris Marina

    Science.gov (United States)

    Mielke, Steven P.; Kiang, Nancy Y.; Blankenship, Robert E.; Mauzerall, David

    2012-01-01

    Acaryochloris marina is the only species known to utilize chlorophyll (Chl) d as a principal photopigment. The peak absorption wavelength of Chl d is redshifted approx. 40 nm in vivo relative to Chl a, enabling this cyanobacterium to perform oxygenic phototrophy in niche environments enhanced in far-red light. We present measurements of the in vivo energy-storage (E-S) efficiency of photosynthesis in A. marina, obtained using pulsed photoacoustics (PA) over a 90-nm range of excitation wavelengths in the red and far-red. Together with modeling results, these measurements provide the first direct observation of the trap energies of PSI and PSII, and also the photosystem-specific contributions to the total E-S efficiency. We find the maximum observed efficiency in A. marina (40+/-1% at 735 nm) is higher than in the Chl a cyanobacterium Synechococcus leopoliensis (35+/-1% at 690 nm). The efficiency at peak absorption wavelength is also higher in A. marina (36+/-1% at 710 nm vs. 31+/-1% at 670 nm). In both species, the trap efficiencies are approx. 40% (PSI) and approx. 30% (PSII). The PSI trap in A. marina is found to lie at 740+/-5 nm, in agreement with the value inferred from spectroscopic methods. The best fit of the model to the PA data identifies the PSII trap at 723+/-3 nm, supporting the view that the primary electron-donor is Chl d, probably at the accessory (ChlD1) site. A decrease in efficiency beyond the trap wavelength, consistent with uphill energy transfer, is clearly observed and fit by the model. These results demonstrate that the E-S efficiency in A. marina is not thermodynamically limited, suggesting that oxygenic photosynthesis is viable in even redder light environments.

  11. Proteomic strategy for the analysis of the polychlorobiphenyl-degrading cyanobacterium Anabaena PD-1 exposed to Aroclor 1254.

    Directory of Open Access Journals (Sweden)

    Hangjun Zhang

    Full Text Available The cyanobacterium Anabaena PD-1, which was originally isolated from polychlorobiphenyl (PCB-contaminated paddy soils, has capabilities for dechlorinatin and for degrading the commercial PCB mixture Aroclor 1254. In this study, 25 upregulated proteins were identified using 2D electrophoresis (2-DE coupled with matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS. These proteins were involved in (i PCB degradation (i.e., 3-chlorobenzoate-3,4-dioxygenase; (ii transport processes [e.g., ATP-binding cassette (ABC transporter substrate-binding protein, amino acid ABC transporter substrate-binding protein, peptide ABC transporter substrate-binding protein, putrescine-binding protein, periplasmic solute-binding protein, branched-chain amino acid uptake periplasmic solute-binding protein, periplasmic phosphate-binding protein, phosphonate ABC transporter substrate-binding protein, and xylose ABC transporter substrate-binding protein]; (iii energetic metabolism (e.g., methanol/ethanol family pyrroloquinoline quinone (PQQ-dependent dehydrogenase, malate-CoA ligase subunit beta, enolase, ATP synthase β subunit, FOF1 ATP synthase subunit beta, ATP synthase α subunit, and IMP cyclohydrolase; (iv electron transport (cytochrome b6f complex Fe-S protein; (v general stress response (e.g., molecular chaperone DnaK, elongation factor G, and translation elongation factor thermostable; (vi carbon metabolism (methanol dehydrogenase and malate-CoA ligase subunit beta; and (vii nitrogen reductase (nitrous oxide reductase. The results of real-time polymerase chain reaction showed that the genes encoding for dioxygenase, ABC transporters, transmembrane proteins, electron transporter, and energetic metabolism proteins were significantly upregulated during PCB degradation. These genes upregulated by 1.26- to 8.98-fold. These findings reveal the resistance and adaptation of cyanobacterium to the presence of PCBs, shedding light on the

  12. Temperature and irradiance influences on cadmium and zinc uptake and toxicity in a freshwater cyanobacterium, Microcystis aeruginosa

    International Nuclear Information System (INIS)

    Zeng Jin; Wang Wenxiong

    2011-01-01

    Highlights: → This study is the first to study the influences of temperature and light irradiance, two critical factors for the occurrence of cyanobacterial blooms, on metal uptake, subcellular distribution, and toxicity in a freshwater cyanobacterium commonly blooming in eutrophic lakes. → With increasing metal exposure, both cellular growth rate and photosynthesis became more sensitive to metal toxicity under elevated irradiance and temperature, primarily as a result of increased uptake and accumulation. → Cd in the metal rich granule faction increased under Cd exposure, suggesting that MRG may partially detoxify Cd in the cyanobacterial cells. → This study implies that temperature and irradiance may influence the chemical cycling of metals during cyanobacterial blooming in eutrophic freshwater ecosystems. - Abstract: Temperature and light irradiance are important factors affecting the occurrence of cyanobacterial blooms. In this study, we examined the influences of different temperatures (15, 24, and 30 ° C ) and irradiances (18, 32, and 55 μmol photons m -2 s -1 ) on the uptake and toxicity of cadmium (Cd) and zinc (Zn) in a freshwater cyanobacterium Microcystis aeruginosa. The subcellular distribution of Cd and Zn was analyzed. Enhanced growth rates were observed for the cyanobacterial cells incubated at higher temperature or irradiance conditions with lower metal concentrations. With increasing ambient Cd or Zn concentrations, both cellular growth rate and photosynthesis were significantly inhibited at elevated irradiance conditions. The observed increase in Cd and Zn toxicity might be attributed to the enhanced metal uptake and accumulation in Microcystis. Based on the intracellular Cd concentration, the 50% inhibition concentration (IC 50 ) values were higher at the higher temperature or irradiance treatment. The subcellular distribution demonstrated that Cd in the metal rich granule (MRG) faction increased with elevated [Cd 2+ ] concentration

  13. Microenvironmental Ecology of the Chlorophyll b-containing Symbiotic Cyanobacterium Prochloron in the Didemnid Ascidian Lissoclinum patella

    Directory of Open Access Journals (Sweden)

    Michael eKühl

    2012-11-01

    Full Text Available The discovery of the cyanobacterium Prochloron was the first finding of a bacterial oxyphototroph with chlorophyll (Chl b, in addition to Chl a. It was first described as Prochloron didemni but a number of clades have since been described. Prochloron is a conspicuously large (7-25 µm unicellular cyanobacterium living in a symbiotic relationship, primarily with (sub- tropical didemnid ascidians; it has resisted numerous cultivation attempts and appears truly obligatory symbiotic. Recently, a Prochloron draft genome was published, revealing no lack of metabolic genes that could explain the apparent inability to reproduce and sustain photosynthesis in a free-living stage. Possibly, the unsuccessful cultivation is partly due to a lack of knowledge about the microenvironmental conditions and ecophysiology of Prochloron in its natural habitat. We used microsensors, variable chlorophyll fluorescence imaging and imaging of O2 and pH to obtain a detailed insight to the microenvironmental ecology and photobiology of Prochloron in hospite in the didemnid ascidian Lissoclinum patella. The microenvironment within ascidians is characterized by steep gradients of light and chemical parameters that change rapidly with varying irradiances. The interior zone of the ascidians harboring Prochloron thus became anoxic and acidic within a few min of darkness, while the same zone exhibited O2 super-saturation and strongly alkaline pH after a few min of illumination. Photosynthesis showed lack of photoinhibition even at high irradiances equivalent to full sunlight, and photosynthesis recovered rapidly after periods of anoxia. We discuss these new insights on the ecological niche of Prochloron and possible interactions with its host and other microbes in light of its recently published genome and a recent study of the overall microbial diversity and metagenome of L. patella.

  14. Dissipative light-bullets in the filamentation of femtosecond pulses

    International Nuclear Information System (INIS)

    Porras, M.A.; Gonzalo, I.

    2010-01-01

    Complete text of publication follows. With the growing interest in filamentation in solid and liquid media, the regime of filamentation with anomalous dispersion is receiving more attention. In this work we show that basics aspects of the filament dynamics in this regime can be explained in terms of a novel type of light-bullet, which is not of solitary or of conical types, but a wave-packet that maximizes the energy dissipation into the medium while remaining localized and stationary in propagation. We first show that a nonlinear optical medium at a given carrier wave length at which dispersion is anomalous, supports 'dissipative' light-bullets, i.e., waves localized in space and time and that propagate without change as a result of a balance between nonlinear compression and nonlinear absorption. Among them, the particular dissipative light-bullet with the highest possible dissipation is unique in a given medium, in the sense that all its properties are fixed by the properties of the medium at the carrier wave length. In this light-bullet, self-focusing continuously transports energy towards the pulse center by an amount that just compensates for the nonlinear losses. Figure 1(a) shows the radial profiles of the dissipative light-bullets that maximizes energy dissipation for several orders of multi-photon absorption responsible for the nonlinear losses. We have also found that this dissipative light-bullet tends to be spontaneously formed in the filamentary dynamics in media with anomalous dispersion. Figure 1(b) shows the peak intensity, the total energy and losses of a pulse that undergoes self-focusing and filamentation in an ideal medium with only Kerr nonlinearity and multi-photon absorption. This simple model reproduces the particularly long filament 'segments' and the 'burst' observed in experiments and in more accurate simulations. The peak intensity in the filament is identical to that of the dissipative light-bullet with maximum dissipation, and the

  15. Comparison of the filament behaviour observed during type I ELMs in ASDEX upgrade and MAST

    International Nuclear Information System (INIS)

    Kirk, A; Ayed, B; Counsell, G F; Lisgo, S; Price, M; Tallents, S; Herrmann, A; Eich, T; Muller, H W; Schmid, A; Wilson, H

    2008-01-01

    A study of the evolution of the filaments observed during Type I ELMs on ASDEX Upgrade and MAST is presented. The filaments start off rotating toroidally/poloidally with velocities close to that of the pedestal. This velocity then decreases as the filaments propagate radially. On both devices the ion saturation current e-folding lengths of the filaments show a weak, if any, dependence on the size of the ELM (δW ELM /W ped ). On MAST the measured radial velocities of the filaments also show at most a weak dependence on δW ELM /W ped

  16. Additive Manufacturing of Syntactic Foams: Part 1: Development, Properties, and Recycling Potential of Filaments

    Science.gov (United States)

    Singh, Ashish Kumar; Patil, Balu; Hoffmann, Niklas; Saltonstall, Brooks; Doddamani, Mrityunjay; Gupta, Nikhil

    2018-03-01

    This work focuses on developing filaments of high-density polyethylene (HDPE) and their hollow particle-filled syntactic foams for commercial three-dimensional (3D) printers based on fused filament fabrication technology. Hollow fly-ash cenospheres were blended by 40 wt.% in a HDPE matrix to produce syntactic foam (HDPE40) filaments. Further, the recycling potential was studied by pelletizing the filaments again to extrude twice (2×) and three times (3×). The filaments were tensile tested at 10-4 s-1, 10-3 s-1, and 10-2 s-1 strain rates. HDPE40 filaments show an increasing trend in modulus and strength with the strain rate. Higher density and modulus were noticed for 2× filaments compared to 1× filaments because of the crushing of some cenospheres in the extrusion cycle. However, 2× and 3× filament densities are nearly the same, showing potential for recycling them. The filaments show better properties than the same materials processed by conventional injection molding. Micro-CT scans show a uniform dispersion of cenospheres in all filaments.

  17. Thick filament mechano-sensing is a calcium-independent regulatory mechanism in skeletal muscle.

    Science.gov (United States)

    Fusi, L; Brunello, E; Yan, Z; Irving, M

    2016-10-31

    Recent X-ray diffraction studies on actively contracting fibres from skeletal muscle showed that the number of myosin motors available to interact with actin-containing thin filaments is controlled by the stress in the myosin-containing thick filaments. Those results suggested that thick filament mechano-sensing might constitute a novel regulatory mechanism in striated muscles that acts independently of the well-known thin filament-mediated calcium signalling pathway. Here we test that hypothesis using probes attached to the myosin regulatory light chain in demembranated muscle fibres. We show that both the extent and kinetics of thick filament activation depend on thick filament stress but are independent of intracellular calcium concentration in the physiological range. These results establish direct control of myosin motors by thick filament mechano-sensing as a general regulatory mechanism in skeletal muscle that is independent of the canonical calcium signalling pathway.

  18. A MAGNETIC RIBBON MODEL FOR STAR-FORMING FILAMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Auddy, Sayantan; Basu, Shantanu [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Kudoh, Takahiro, E-mail: sauddy3@uwo.ca, E-mail: basu@uwo.ca, E-mail: kudoh@nagasaki-u.ac.jp [Faculty of Education, Nagasaki University, 1-14 Bunkyo-machi, Nagasaki 852-8521 (Japan)

    2016-11-01

    We develop a magnetic ribbon model for molecular cloud filaments. These result from turbulent compression in a molecular cloud in which the background magnetic field sets a preferred direction. We argue that this is a natural model for filaments and is based on the interplay between turbulence, strong magnetic fields, and gravitationally driven ambipolar diffusion, rather than pure gravity and thermal pressure. An analytic model for the formation of magnetic ribbons that is based on numerical simulations is used to derive a lateral width of a magnetic ribbon. This differs from the thickness along the magnetic field direction, which is essentially the Jeans scale. We use our model to calculate a synthetic observed relation between apparent width in projection versus observed column density. The relationship is relatively flat, similar to observations, and unlike the simple expectation based on a Jeans length argument.

  19. Electromagnetic effects on plasma blob-filament transport

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Wonjae, E-mail: wol023@ucsd.edu [University of California, San Diego, La Jolla, CA (United States); Angus, J.R. [Naval Research Laboratory, Washington, DC (United States); Umansky, Maxim V. [Lawrence Livermore National Laboratory, Livermore, CA (United States); Krasheninnikov, Sergei I. [University of California, San Diego, La Jolla, CA (United States); Nuclear Research National University MEPhI, Moscow 115409 (Russian Federation)

    2015-08-15

    Both microscopic and macroscopic impacts of the electromagnetic effects on blob dynamics are considered. Linear stability analysis and nonlinear BOUT++ simulations demonstrate that electromagnetic effects in high temperature or high beta plasmas suppress the resistive drift wave turbulence in the blob when resistivity drops below a certain value. In the course of blob’s motion in the SOL its temperature is reduced, which leads to enhancement of resistive effects, so the blob can switch from electromagnetic to electrostatic regime, where resistive drift wave turbulence become important. It is found that inhomogeneity of magnetic curvature or plasma pressure along the filament length leads to bending of the high-beta blob filaments. This is caused by the increase of the propagation time of plasma current (Alfvén time) in higher-density plasma. The effects of sheath boundary conditions on the part of the blob away from the boundary are also diminished by the increased Alfvén time.

  20. Mineralized remains of morphotypes of filamentous cyanobacteria in carbonaceous meteorites

    Science.gov (United States)

    Hoover, Richard B.

    2005-09-01

    The quest for conclusive evidence of microfossils in meteorites has been elusive. Abiotic microstructures, mineral grains, and even coating artifacts may mimic unicellular bacteria, archaea and nanobacteria with simple spherical or rod morphologies (i.e., cocci, diplococci, bacilli, etc.). This is not the case for the larger and more complex microorganisms, colonies and microbial consortia and ecosystems. Microfossils of algae, cyanobacteria, and cyanobacterial and microbial mats have been recognized and described from many of the most ancient rocks on Earth. The filamentous cyanobacteria and sulphur-bacteria have very distinctive size ranges, complex and recognizable morphologies and visibly differentiated cellular microstructures. The taphonomic modes of fossilization and the life habits and processes of these microorganisms often result in distinctive chemical biosignatures associated with carbonization, silicification, calcification, phosphatization and metal-binding properties of their cell-walls, trichomes, sheaths and extracellular polymeric substances (EPS). Valid biogenicity is provided by the combination of a suite of known biogenic elements (that differ from the meteorite matrix) found in direct association with recognizable and distinct biological features and microstructures (e.g., uniseriate or multiseriate filaments, trichomes, sheaths and cells of proper size/size range); specialized cells (e.g., basal or apical cells, hormogonia, akinetes, and heterocysts); and evidence of growth characteristics (e.g., spiral filaments, robust or thin sheaths, laminated sheaths, true or false branching of trichomes, tapered or uniform filaments) and evidence of locomotion (e.g. emergent cells and trichomes, coiling hormogonia, and hollow or flattened and twisted sheaths). Since 1997 we have conducted Environmental and Field Emission Scanning Electron Microscopy (ESEM and FESEM) studies of freshly fractured interior surfaces of carbonaceous meteorites, terrestrial