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Cyanobacteria
Kinds of Cyanobacteria Selected AbstractsA BATCH CULTURE METHOD FOR MICROALGAE AND CYANOBACTERIA WITH CO2 SUPPLY THROUGH POLYETHYLENE MEMBRANES,JOURNAL OF PHYCOLOGY, Issue 4 2010Yvonne Pörs A new method for CO2 supply to photoautotrophic organisms was developed, and its applicability for measuring specific growth rates in shaken batch cultures of cyanobacteria and unicellular algae was shown. Small bags containing a concentrated carbonate buffer with a CO2 partial pressure of 32 mbar were prepared from a thin foil of low density polyethylene (LDPE). These bags were inserted as CO2 reservoirs (CRs) into polystyrene culture flasks with gas-permeable screw caps, which were suitable to photometric growth measurement. CO2 was released directly into the medium with membrane-controlled kinetics. The CRs were not depleted within 1 week, although the atmosphere in the culture vessel exchanged rapidly with the ambient air. Rates of initial growth and final densities of the cultures of six different unicellular algal species and one cyanobacterium were markedly increased by diffusive CO2 supply from the CR. In the presence of a CR, growth was exponential during the first 2 d in all cultures studied. The method described allowed a high number of measurements of specific growth rates with relatively simple experimental setup. [source] MEASUREMENT OF IN SITU SPECIFIC GROWTH RATES OF MICROCYSTIS (CYANOBACTERIA) FROM THE FREQUENCY OF DIVIDING CELLS,JOURNAL OF PHYCOLOGY, Issue 5 2009Yoshimasa Yamamoto Diel changes in the frequency of dividing cells (FDC) of three Microcystis species were investigated in a small eutrophic pond from July to October 2005. The representative species was M. aeruginosa (Kütz.) Kütz., constituting 57%,86% of the Microcystis population throughout the study period, and the remainder were M. viridis (A. Braun) Lemmerm. and M. wesenbergii (Komárek) Komárek. The FDC of M. aeruginosa and M. wesenbergii increased in the daytime and fell in the nighttime in July and August, but this regular variation was not observed in September or October. The in situ specific growth rates of Microcystis species were estimated based on the assumption that the specific growth rate can be given as an absolute value of the derivative of FDC with respect to time. The calculated values were similar among species,0.15,0.38 ˇ d,1 for M. aeruginosa, 0.14,0.63 ˇ d,1 for M. viridis, and 0.18,0.61 ˇ d,1 for M. wesenbergii. The specific growth rates in July and August slightly exceeded those in September and October. The analysis of the in situ specific growth rate of Microcystis indicated that recruitment of the benthic population or morphological change, rather than massive growth, was at least partly responsible for the dominance of M. aeruginosa in the study pond. [source] GEITLERINEMA SPECIES (OSCILLATORIALES, CYANOBACTERIA) REVEALED BY CELLULAR MORPHOLOGY, ULTRASTRUCTURE, AND DNA SEQUENCING,JOURNAL OF PHYCOLOGY, Issue 3 2009Maria Do Carmo Bittencourt-Oliveira Geitlerinema amphibium (C. Agardh ex Gomont) Anagn. and G. unigranulatum (Rama N. Singh) Komárek et M. T. P. Azevedo are morphologically close species with characteristics frequently overlapping. Ten strains of Geitlerinema (six of G. amphibium and four of G. unigranulatum) were analyzed by DNA sequencing and transmission electronic and optical microscopy. Among the investigated strains, the two species were not separated with respect to cellular dimensions, and cellular width was the most varying characteristic. The number and localization of granules, as well as other ultrastructural characteristics, did not provide a means to discriminate between the two species. The two species were not separated either by geography or environment. These results were further corroborated by the analysis of the cpcB- cpcA intergenic spacer (PC-IGS) sequences. Given the fact that morphology is very uniform, plus the coexistence of these populations in the same habitat, it would be nearly impossible to distinguish between them in nature. On the other hand, two of the analyzed strains were distinct from all others based on the PC-IGS sequences, in spite of their morphological similarity. PC-IGS sequences indicate that these two strains could be a different species of Geitlerinema. Using morphology, cell ultrastructure, and PC-IGS sequences, it is not possible to distinguish G. amphibium and G. unigranulatum. Therefore, they should be treated as one species, G. unigranulatum as a synonym of G. amphibium. [source] CHANGES IN THE MORPHOLOGY AND POLYSACCHARIDE CONTENT OF MICROCYSTIS AERUGINOSA (CYANOBACTERIA) DURING FLAGELLATE GRAZING,JOURNAL OF PHYCOLOGY, Issue 3 2008Zhou Yang To investigate the changes in the morphology and polysaccharide content of Microcystis aeruginosa (Kütz.) Kütz. during flagellate grazing, cultures of M. aeruginosa were exposed to grazing Ochromonas sp. for a period of 9 d under controlled laboratory conditions. M. aeruginosa responded actively to flagellate grazing and formed colonies, most of which were made up of several or dozens of cells, suggesting that flagellate grazing may be one of the biotic factors responsible for colony formation in M. aeruginosa. When colonies were formed, the cell surface ultrastructure changed, and the polysaccharide layer on the surface of the cell wall became thicker. This change indicated that synthesis and secretion of extracellular polysaccharide (EPS) of M. aeruginosa cells increased under flagellate grazing pressure. The contents of soluble extracellular polysaccharide (sEPS), bound extracellular polysaccharide (bEPS), and total polysaccharide (TPS) in colonial cells of M. aeruginosa increased significantly compared with those in single cells. This finding suggested that the increased amount of EPS on the cell surface may play a role in keeping M. aeruginosa cells together to form colonies. [source] MICROALGAE AND CYANOBACTERIA: FOOD FOR THOUGHT,JOURNAL OF PHYCOLOGY, Issue 2 2008Miroslav Gantar In non-Western civilizations, cyanobacteria have been part of the human diet for centuries. Today, microalgae and cyanobacteria are either produced in controlled cultivation processes or harvested from the natural habitats and marketed as food supplements around the world. Cyanobacteria produce a vast array of different biologically active compounds, some of which are expected to be used in drug development. The fact that some of the active components from cyanobacteria potentially have anticancer, antimicrobial, antiviral, anti-inflammatory, and other effects is being used for marketing purposes. However, introduction of these products in the form of whole biomass for alimentary purposes raises concerns regarding the potential toxicity and long-term effects on human health. Here, we review data on the use of cyanobacteria and microalgae in human nutrition and searched for available information on legislature that regulates the use of these products. We have found that, although the quality control of these products is most often self-regulated by the manufacturers, different governmental agencies are introducing strict regulations for placing novel products, such as algae and cyanobacteria, on the market. The existing regulations require these products to be tested for the presence of toxins, such as microcystin; however, other, sometimes novel, toxins remain undetected, and their long-term effects on human health remain unknown. [source] SHIFT FROM CHLOROPHYTES TO CYANOBACTERIA IN BENTHIC MACROALGAE ALONG A GRADIENT OF NITRATE DEPLETION,JOURNAL OF PHYCOLOGY, Issue 1 2008Chantal Vis A survey of the spatial distribution of benthic macroalgae in a fluvial lake of the St. Lawrence River (Lake Saint-Pierre, Quebec, Canada) revealed a shift in composition from chlorophytes to cyanobacteria along the flow path of nutrient-rich waters originating from tributaries draining farmlands. The link between this shift and changes in water quality characteristics was investigated by sampling at 10 sites along a 15 km transect. Conductivity, current, light extinction, total phosphorus (TP; >25 ,g P ˇ L,1), and ammonium (8,21 ,g N ˇ L,1) remained fairly constant along the transect in contrast to nitrate concentrations, which fell sharply. Filamentous and colonial chlorophytes [Cladophora sp. and Hydrodictyon reticulatum (L.) Bory] dominated in the first 5 km where nitrate concentrations were >240 ,g N ˇ L,1. A mixed assemblage of chlorophytes and cyanobacteria characterized a 1 km transition zone where nitrate decreased to 40,80 ,g N ˇ L,1. In the last section of the transect, nitrate concentrations dropped below 10 ,g N ˇ L,1, and cyanobacteria (benthic filamentous mats of Lyngbya wollei Farl. ex Gomont and epiphytic colonies of Gloeotrichia) dominated the benthic community. The predominance of nitrogen-fixing, potentially toxic cyanobacteria likely resulted from excessive nutrient loads and may affect nutrient and trophic dynamics in the river. [source] SEDIMENTARY IMPRINT OF MICROCYSTIS AERUGINOSA (CYANOBACTERIA) BLOOMS IN GRANGENT RESERVOIR (LOIRE, FRANCE),JOURNAL OF PHYCOLOGY, Issue 3 2007Delphine Latour Analysis of a sediment core taken from the Grangent reservoir in 2004 showed the presence of high concentrations of Microcystis aeruginosa Kütz. colonies at the sediment surface (250 colonies,ˇ,mL sediment,1) and also at depths of 25,35 cm (2300 coloniesˇmL sediment,1) and 70 cm (600 colonies,ˇ,mL sediment,1). Measurements of radioactive isotopes (7Be, 137Cs, and 241Am) along with photographic analysis of the core were used to date the deep layers: the layer located at ,30 cm dates from summer 2003, and that located at ,70 cm from 1990 to 1991. The physiological and morphological conditions of those benthic colonies were compared with those of planktonic colonies using several techniques (environmental scanning electron microscopy [ESEM], TEM, DNA markers, cellular esterases, and toxins). The ESEM observations showed that, as these colonies age, peripheral cells disappear, with no cells remaining in the mucilage of the deepest colonies (70 cm), an indication of the survival thresholds of these organisms. In the benthic phase, the physiological conditions (enzyme activity, cell division, and intracellular toxins) and ultrastructure (particularly the gas vesicles) of the cells surviving in the heart of the colony are comparable to those of the planktonic form, with all the potential needed for growth. Maintaining cellular integrity requires a process that can provide sufficient energy and is expressed in the reduced, but still existing, enzymatic activity that we measured, which is equivalent to a quiescent state. [source] UNIVERSAL PRIMERS AMPLIFY A 23S rDNA PLASTID MARKER IN EUKARYOTIC ALGAE AND CYANOBACTERIA,JOURNAL OF PHYCOLOGY, Issue 3 2007Alison R. Sherwood The challenge in the development of universal algal primers lies in the genetic diversity contained within the vast array of evolutionary lineages present in this informally named group of organisms. A comparative genomics approach was used previously to identify conserved primers flanking a region of the plastid genome. Our present research illustrates the feasibility of amplifying and sequencing this marker across multiple algal lineages. We present a preliminary framework of 107 novel sequences of this region from 62 red algae, 19 green algae, 14 brown algae, 8 cyanobacteria, 2 diatoms, 1 xanthophyte, and 1 euglenoid, and illustrate levels of divergence of the marker for well-represented groups in a neighbor-joining analysis. This ,410 nt region distinguishes most species included in the analysis. The remarkable universality of these primers suggests potential for their use in assays of environmental samples in which they could be used to simultaneously detect a number of different algal lineages. [source] SIMPLE METHOD FOR RNA PREPARATION FROM CYANOBACTERIA,JOURNAL OF PHYCOLOGY, Issue 5 2006Byung-Hyuk Kim A simple and rapid method is presented for the preparation of RNA from various cyanobacteria. Unlike other methods that require a lysis solution, lysozymes, or proteinase K, the proposed method, called the bead,phenol,chloroform (BPC) method, uses silica/zirconia beads, phenol, and chloroform to break the cells and extract RNA more efficiently. Experiments confirm that the BPC method can successfully isolate total RNA from various cyanobacterial strains without DNA contamination, and the extracted RNA samples have a relatively high purity, concentration, and yield. Furthermore, the BPC method is more rapid, simple, and economical when compared with previously reported methods. [source] EXAMINATION OF DIEL CHANGES IN GLOBAL TRANSCRIPT ACCUMULATION IN SYNECHOCYSTIS (CYANOBACTERIA),JOURNAL OF PHYCOLOGY, Issue 3 2006Rochelle G. Labiosa Phytoplankton in nature must acclimate to a wide range of light conditions resulting from diel light cycles, ocean circulation and mixing, cloud cover, and the variable bio-optical characteristics of the water column. In this study, we used whole-genome cDNA microarrays to investigate the effects of a gradually fluctuating daily light cycle on gene expression in the cyanobacterium Synechocystis sp. strain PCC6803. From these data, we developed a conceptual framework depicting the diel regulation of metabolic pathways in the cell. The framework is focused on potential photoacclimation responses, including the regulation of the photosystems, cell division, and DNA replication. The mRNA abundance of genes involved in many metabolic pathways, and particularly those encoding proteins that function in photosynthesis and DNA replication, changed markedly over the course of the day. The levels of mRNA encoding polypeptides important for the formation of the light-harvesting apparatus, photosystems I and II, and cell division were found in high concentrations during the day. The transcript levels of many genes encoding enzymes involved in anabolic processes also increased considerably during the day. In contrast, transposon transcripts and mRNAs encoding proteins involved in DNA replication, cell wall synthesis, and respiratory activity were not found in high concentrations during the day. Although gradually varying light exposure induced significant changes in transcript accumulation within Synechocystis, the direction of these changes differed between our study and previous studies in which there was an abrupt transition between irradiances. [source] LATERAL GENE TRANSFER IN THE CYANOBACTERIA: CHLOROPHYLLS, PROTEINS, AND SCRAPS OF RIBOSOMAL RNAJOURNAL OF PHYCOLOGY, Issue 3 2005B. R. Green First page of article [source] THE CYANOTOXINS-BIOACTIVE METABOLITES OF CYANOBACTERIA: OCCURRENCE, ECOLOGICAL ROLE, TAXONOMIC CONCERNS AND EFFECTS ON HUMANSJOURNAL OF PHYCOLOGY, Issue 2001Article first published online: 24 SEP 200 Carmichael, W. W. Department of Biological Sciences, Wright State University, Dayton, Ohio 45435 USA Cyanobacteria toxins (cyanotoxins) include cytotoxins and biotoxins with cytotoxins including about 60 compounds ranging from phytoalexins to animicrobials to enzyme inhibitors to compounds that can reverse multidrug resistance. Producer organisms include marine/brackish water Cystoseira, Hormothamnin, Lyngbya, Nodularia and Synechocystis, and the freshwater/terrestrial genera Anabaena, Dichotrix, Fischerella, Hapalosiphon, Lyngbya, Microcystis, Nostoc, Oscillatoria, Planktothrix, Phormidium, Schizothrix, Scytonema, Spirulina, Stigonema and Symploca. Since many of these compounds have been identified, not during ecological studies, but during drug discovery investigations, their ecological role is only speculative. Biotoxins are responsible for acute lethal, acute, chronic and sub-chronic poisonings of wild/domestic animals and humans. They include the neurotoxins; anatoxin-a, anatoxin-a(s) and saxitoxins plus the hepatotoxins; microcystins, nodularins and cylindrospermopsin. These compounds are included when referencing harmful algal blooms (HAB's) such as the more predominate marine PSP (paralytic shellfish poisoning), DSP (diarrhetic shellfish poisoning), NSP (neurotoxic shellfish poisoning), ASP (amnesic shellfish poisoning) and EAS (estuary associated syndrome). The CTP (cyanobacteria toxin poisoning) organisms occur in freshwater lakes, ponds, rivers and reservoirs throughout the world. Organisms responsible for CTP's are Anabaena, Aphanizomenon, Cylindrosperm- opsis, Microcystis, Nodularia, Nostoc Oscillatoria (Planktothrix), Trichodesmium and certain picoplanktic genera. Concern for animal and human health impairments arises from animal poisonings, associated with cyanobacteria waterblooms, beginning with the later part of the 1800's. It was not until the 1950's that we began to understand that cyanobacteria could indeed produce highly toxic compounds. A recent 1998 compilation of all available information on toxic cyanobacteria was published by the World Health Organization. This increasing focus on the role of cyanobacteria metabolites in chemical ecology, drug discovery and toxinology has placed new importance on using correct taxonomy for communication of responsible organisms. [source] SOME PHYLOGENETIC RELATIONSHIPS WITHIN THE OSCILLATORIALES (CYANOBACTERIA) CLADE USING 16S RDNA GENE SEQUENCE DATAJOURNAL OF PHYCOLOGY, Issue 2000D.A. Casamatta An approximately 1400 base pair region of the 16S rDNA gene was sequenced from taxa within the Oscillatoriales in order to assess phylogenetic relationships. Ten previously unsequenced strains were obtained from the University of Toronto Culture Collection. New sequence data were combined with previously published sequences from a wide representation of cyanobacteria including all currently available, complete Oscillatorialian taxa. Trees constructed using parsimony, distance, and maximum likelihood methods were similar in topology, although a few taxa were variable in their placement depending on the phylogenetic method employed. Newly sequenced taxa of the genera Phormidium, Oscillatoria, and Lyngbya did not form monophyletic clades based on traditional generic designations. Two Lyngbya strains (UTCC296 and 313) and Phormidium subfuscum (UTCC474) formed a well supported monophyletic clade, but the affinity of this clade with other groups was uncertain due to lack of bootstrap support. Oscillatoria sp. (UTCC393) was closely related to the previously sequenced Oscillatoria limnetica and likewise, Phormidium molle (UTCC77) and Phormidium tenue (UTCC473) were placed in a well supported clade with other Oscillatoriales. The other four taxa were variously placed in the trees and their phylogenetic positions could not be determined with certainty. [source] 4-Aminothiophenol Self-Assembled Monolayer for the Development of a DNA Biosensor Aiming the Detection of Cylindrospermopsin Producing CyanobacteriaELECTROANALYSIS, Issue 22 2008Elisabete Valério Abstract The development of a DNA biosensor for the detection of cylindrospermopsin, based on self-assembled monolayers (SAMs) of 4-aminothiophenol, is investigated. SAMs were characterized by electrochemical reductive desorption. Detection of probe immobilization and hybridization has been achieved by cyclic and square-wave voltammetry (SWV), using methylene blue (MB) as electroactive indicator. The SWV data obtained in phosphate buffer, with and without NaCl, after MB accumulation, revealed an increase of the redox indicator current peaks after the hybridization step. This behavior is consistent with MB intercalation into DNA, for high ionic strength media and attributed to electrostatic interactions in the absence of salt. Evidence for surface modification is also provided by atomic force microscopy and ellipsometry. [source] Comparative Study of Cyanobacteria as Biocatalysts for the Asymmetric Synthesis of Chiral Building BlocksENGINEERING IN LIFE SCIENCES (ELECTRONIC), Issue 2 2006J. Havel Abstract The three representative cyanobacteria, Synechococcus PCC7942, Anabaena variabilis, and Nostoc muscorum, were studied for their ability to asymmetrically reduce the prochiral ketones 2,-3,-4,-5,-6,-pentafluoroacetophenone, ethyl 4-chloroacetate, 4-chloroacetophenone, and ethylbenzoylacetate to the corresponding chiral alcohols. Photosynthesis as well as respiration was applied for intracellular regeneration of the NAD(P)H cofactor. It was shown for the first time that all cyanobacteria were able to reduce the prochiral ketones asymmetrically without light for cofactor regeneration. By comparison of the cell specific product formation capacities of cyanobacteria with typical heterotrophic whole cell biocatalysts in batch processes, it is shown that comparable or, in some cases, better performances at high enantiomeric excess (ee > 99.8,%) are obtained. As a consequence of a generally strong product inhibition, in situ product removal must be applied in order to restore process efficiency when using cyanobacteria as biocatalysts. [source] Widespread known and novel phosphonate utilization pathways in marine bacteria revealed by functional screening and metagenomic analysesENVIRONMENTAL MICROBIOLOGY, Issue 1 2010Asuncion Martinez Summary Phosphonates (Pn), compounds with a direct C,P bond instead of the more common C,O,P ester bond, constitute a significant fraction of marine dissolved organic phosphorus and recent evidence suggests that they may be an alternative source of P for marine microorganisms. To further characterize the microorganisms and pathways involved in Pn utilization, we screened bacterioplankton genomic libraries for their ability to complement an Escherichia coli strain unable to use Pns as a P source. Using this approach we identified a phosphonatase pathway as well as a novel pair of genes that allowed utilization of 2-aminoethylphosphonate (2-AEPn) as the sole P source. These pathways are present in diverse bacteria common in marine plankton including representatives of Proteobacteria, Planctomycetes and Cyanobacteria. Analysis of metagenomic databases for Pn utilization genes revealed that they are widespread and abundant among marine bacteria, suggesting that Pn metabolism is likely to play an important role in P-depleted surface waters, as well as in the more P-rich deep-water column. [source] Is the distribution of nitrogen-fixing cyanobacteria in the oceans related to temperature?ENVIRONMENTAL MICROBIOLOGY, Issue 7 2009Lucas J. Stal Summary Approximately 50% of the global natural fixation of nitrogen occurs in the oceans supporting a considerable part of the new primary production. Virtually all nitrogen fixation in the ocean occurs in the tropics and subtropics where the surface water temperature is 25°C or higher. It is attributed almost exclusively to cyanobacteria. This is remarkable firstly because diazotrophic cyanobacteria are found in other environments irrespective of temperature and secondly because primary production in temperate and cold oceans is generally limited by nitrogen. Cyanobacteria are oxygenic phototrophic organisms that evolved a variety of strategies protecting nitrogenase from oxygen inactivation. Free-living diazotrophic cyanobacteria in the ocean are of the non-heterocystous type, namely the filamentous Trichodesmium and the unicellular groups A,C. I will argue that warm water is a prerequisite for these diazotrophic organisms because of the low-oxygen solubility and high rates of respiration allowing the organism to maintain anoxic conditions in the nitrogen-fixing cell. Heterocystous cyanobacteria are abundant in freshwater and brackish environments in all climatic zones. The heterocyst cell envelope is a tuneable gas diffusion barrier that optimizes the influx of both oxygen and nitrogen, while maintaining anoxic conditions inside the cell. It is not known why heterocystous cyanobacteria are absent from the temperate and cold oceans and seas. [source] Culture-independent evidence for the persistent presence and genetic diversity of microcystin-producing Anabaena (Cyanobacteria) in the Gulf of FinlandENVIRONMENTAL MICROBIOLOGY, Issue 4 2009David P. Fewer Summary The late summer mass occurrences of cyanobacteria in the Baltic Sea are among the largest in the world. These blooms are rarely monotypic and are often composed of a diverse assemblage of cyanobacteria. The toxicity of the blooms is attributed to Nodularia spumigena through the production of the hepatotoxic nodularin. However, the microcystin hepatotoxins have also been reported from the Baltic Sea on a number of occasions. Recent evidence links microcystin production in the Gulf of Finland directly to the genus Anabaena. Here we developed a denaturing gradient gel electrophoresis (DGGE) method based on the mcyE microcystin synthetase gene and ndaF nodularin synthetase gene that allows the culture-independent discrimination of microcystin- and nodularin-producing cyanobacteria directly from environmental samples. We PCR-amplified microcystin and nodularin synthetase genes from environmental samples taken from the Gulf of Finland and separated them on a denaturing gradient gel using optimized conditions. Sequence analyses demonstrate that uncultured microcystin-producing Anabaena strains are genetically more diverse than previously demonstrated from cultured strains. Furthermore, our data show that microcystin-producing Anabaena are widespread in the open Gulf of Finland. Non-parametric statistical analysis suggested that salinity plays an important role in defining the distribution of microcystin-producing Anabaena. Our results indicate that microcystin-producing blooms are a persistent phenomenon in the Gulf of Finland. [source] Soil CO2 flux and photoautotrophic community composition in high-elevation, ,barren' soilENVIRONMENTAL MICROBIOLOGY, Issue 3 2009Kristen R. Freeman Summary Soil-dominated ecosystems, with little or no plant cover (i.e. deserts, polar regions, high-elevation areas and zones of glacial retreat), are often described as ,barren', despite their potential to host photoautotrophic microbial communities. In high-elevation, subnival zone soil (i.e. elevations higher than the zone of continuous vegetation), the structure and function of these photoautotrophic microbial communities remains essentially unknown. We measured soil CO2 flux at three sites (above 3600 m) and used molecular techniques to determine the composition and distribution of soil photoautotrophs in the Colorado Front Range. Soil CO2 flux data from 2002 and 2007 indicate that light-driven CO2 uptake occurred on most dates. A diverse community of Cyanobacteria, Chloroflexi and eukaryotic algae was present in the top 2 cm of the soil, whereas these clades were nearly absent in deeper soils (2,4 cm). Cyanobacterial communities were composed of lineages most closely related to Microcoleus vaginatus and Phormidium murrayi, eukaryotic photoautotrophs were dominated by green algae, and three novel clades of Chloroflexi were also abundant in the surface soil. During the light hours of the 2007 snow-free measurement period, CO2 uptake was conservatively estimated to be 23.7 g C m,2 season,1. Our study reveals that photoautotrophic microbial communities play an important role in the biogeochemical cycling of subnival zone soil. [source] Diversity and expression of nitrogen fixation genes in bacterial symbionts of marine spongesENVIRONMENTAL MICROBIOLOGY, Issue 11 2008Naglaa M. Mohamed Summary Marine sponges contain complex assemblages of bacterial symbionts, the roles of which remain largely unknown. We identified diverse bacterial nifH genes within sponges and found that nifH genes are expressed in sponges. This is the first demonstration of the expression of any protein-coding bacterial gene within a sponge. Two sponges Ircinia strobilina and Mycale laxissima were collected from Key Largo, Florida and had ,15N values of c. 0,1, and 3,4, respectively. The potential for nitrogen fixation by symbionts was assessed by amplification of nifH genes. Diverse nifH genes affiliated with Proteobacteria and Cyanobacteria were detected, and expression of nifH genes affiliated with those from cyanobacteria was detected. The nifH genes from surrounding seawater were similar to those of Trichodesmium and clearly different from the cyanobacterial nifH genes detected in the two sponges. This study advances understanding of the role of bacterial symbionts in sponges and suggests that provision of fixed nitrogen is a means whereby symbionts benefit sponges in nutrient-limited reef environments. Nitrogen fixation by sponge symbionts is possibly an important source of new nitrogen to the reef environment that heretofore has been neglected and warrants further investigation. [source] Isolation and gene quantification of heterotrophic N2 -fixing bacterioplankton in the Baltic SeaENVIRONMENTAL MICROBIOLOGY, Issue 1 2007Kjärstin H. Boström Summary Cyanobacteria are regarded as the main N2 -fixing organisms in marine waters. However, recent clone libraries from various oceans show a wide distribution of the dinitrogenase reductase gene (nifH) originating from heterotrophic bacterioplankton. We isolated heterotrophic N2 -fixing bacteria from Baltic Sea bacterioplankton using low-nitrogen plates and semi-solid diazotroph medium (SSDM) tubes. Isolates were analysed for the nitrogenase (nifH) gene and active N2 fixation by nested polymerase chain reaction (PCR) and acetylene reduction respectively. A primer-probe set targeting the nifH gene from a , - proteobacterial isolate, 97% 16S rDNA similarity to Pseudomonas stutzeri, was designed for measuring in situ dynamics using quantitative real-time PCR. This nifH gene sequence was detected at two of 11 stations in a Baltic Proper transect at abundances of 3 × 104 and 0.8 × 103 copies per litre seawater respectively. Oxygen requirements of isolates were examined by cultivation in SSDM tubes where oxygen gradients were determined with microelectrodes. Growth, and thereby N2 fixation, was observed as horizontal bands formed at oxygen levels of 0,6% air saturation. The apparent microaerophilic or facultative anaerobic nature of the isolates explains why the SSDM approach is the most appropriate isolation method. Our study illustrates how combined isolation, functional analyses and in situ quantification yielded insights into the oxygen requirements of heterotrophic N2 -fixing bacterioplankton isolates, which were confirmed to be present in situ. [source] Highly diverse community structure in a remote central Tibetan geothermal spring does not display monotonic variation to thermal stressFEMS MICROBIOLOGY ECOLOGY, Issue 1 2006Lau Chui Yim Abstract We report an assessment of whole-community diversity for an extremely isolated geothermal location with considerable phylogenetic and phylogeographic novelty. We further demonstrate, using multiple statistical analyses of sequence data, that the response of community diversity is not monotonic to thermal stress along a gradient of 52,83°C. A combination of domain- and division-specific PCR was used to obtain a broad spectrum of community phylotypes, which were resolved by denaturing gradient gel electrophoresis. Among 58 sequences obtained from microbial mats and streamers, some 95% suggest novel archaeal and bacterial diversity at the species level or higher. Moreover, new phylogeographic and thermally defined lineages among the Cyanobacteria, Chloroflexi, Eubacterium and Thermus are identified. Shannon,Wiener diversity estimates suggest that mats at 63°C supported highest diversity, but when alternate models were applied [Average Taxonomic Distinctness (AvTD) and Variation in Taxonomic Distinctness (VarTD)] that also take into account the phylogenetic relationships between phylotypes, it is evident that greatest taxonomic diversity (AvTD) occurred in streamers at 65,70°C, whereas greatest phylogenetic distance between taxa (VarTD) occurred in streamers of 83°C. All models demonstrated that diversity is not related to thermal stress in a linear fashion. [source] Characterization of bacterial communities in four freshwater lakes differing in nutrient load and food web structureFEMS MICROBIOLOGY ECOLOGY, Issue 2 2005Katleen van der Gucht Abstract The phylogenetic composition of bacterioplankton communities in the water column of four shallow eutrophic lakes was analyzed by partially sequencing cloned 16S rRNA genes and by PCR-DGGE analysis. The four lakes differed in nutrient load and food web structure: two were in a clearwater state and had dense stands of submerged macrophytes, while two others were in a turbid state characterized by the occurrence of phytoplankton blooms. One turbid and one clearwater lake had very high nutrient levels (total phosphorus > 100 ,g/l), while the other lakes were less nutrient rich (total phosphorus < 100,g/l). Cluster analysis, multidimensional scaling and ANOSIM (analysis of similarity) were used to investigate differences among the bacterial community composition in the four lakes. Our results show that each lake has its own distinct bacterioplankton community. The samples of lake Blankaart differed substantially from those of the other lakes; this pattern was consistent throughout the year of study. The bacterioplankton community composition in lake Blankaart seems to be less diverse and less stable than in the other three lakes. Clone library results reveal that Actinobacteria strongly dominated the bacterial community in lake Blankaart. The relative abundance of Betaproteobacteria was low, whereas this group was dominant in the other three lakes. Turbid lakes had a higher representation of Cyanobacteria, while clearwater lakes were characterized by more representatives of the Bacteroidetes. Correlating our DGGE data with environmental parameters, using the BIOENV procedure, suggests that differences are partly related to the equilibrium state of the lake. [source] High prokaryote diversity and analysis of community structure in mobile mud deposits off French Guiana: identification of two new bacterial candidate divisionsFEMS MICROBIOLOGY ECOLOGY, Issue 3 2001Vanessa M. Madrid Abstract Bacterial and archaeal community compositions in highly mobile nearshore muds typical of the Guiana coastline of South America were examined by sequence analysis of a 16S rDNA clone library. DNA was extracted from a subsurface sediment layer (10,30 cm) collected at a subtidal (,1 m deep) mud wave site between Kourou and Sinnamary, French Guiana. Analysis of 96 non-chimeric sequences showed the majority to be bacteria (98%), that diversity was high with 64 unique sequences, and that proteobacteria were dominant (46%). Two crenarchaeota sequences were found (2%). Bacterial sequences belonged to the Cytophaga-Flexibacter-Bacteroides (18%), Actinobacteria (11.5%), Planctomycetes (6.3%), Cyanobacteria (3.2%), low-GC Gram-positive (1%), ,, , and , subdivisions of Proteobacteria (27%, 16%, and 9%, respectively). Additional bacterial sequences belonged to the candidate division TM6 (1%) and to two newly proposed candidate divisions: KS-A (2%) and KS-B (3%). A sizeable fraction (22%) of sequences from the Kourou,Sinnamary library are normally found in water column populations, reflecting frequent entrainment of suspended debris into physically reworked underlying sediments. Dominant sequences (56%) were related to Gelidibacter algens (Cytophaga-Flexibacter-Bacteroides group), Actinobacteria, Sulfitobacter and Ruegeria spp. (,-proteobacteria), all of which are chemoorganotrophs, consistent with abundant labile organic carbon. The presence of sequences from potential sulfate reducers and sulfide oxidizers suggests the likelihood of sulfur cycling in these sediments, despite the dominance of suboxic (iron-reducing), non-sulfidic diagenetic properties. Rarefaction analysis indicated that bacterial diversity in the French Guiana library is not only unusually high in comparison with other marine sedimentary environments, but among the most diverse of all environments reported to date. [source] N2 -fixation and complementary chromatic adaptation in non-heterocystous cyanobacteria from Lake ConstanceFEMS MICROBIOLOGY ECOLOGY, Issue 2 2001Christine Postius Abstract Non-heterocystous, mostly filamentous cyanobacteria were isolated from the crust of stones, from the periphyton of two macrophytes from the littoral zone and from the pelagic environment of Lake Constance. All isolates were cultivated as unialgal strains. DNA analysis by restriction fragment length polymorphism with the psbA gene probe revealed high genetic diversity among the strains from the littoral zone. For all genotypes, the occurrence of the nifH gene encoding a nitrogenase subunit and of genes encoding subunits of phycoerythrin and phycocyanin were tested by Southern blot hybridization. In addition, the isolates were investigated for their ability for complementary chromatic adaptation (CCA) and for anaerobic N2 -fixation. With respect to these characteristics, all cyanobacteria included in this study were assigned to four different types: (1) strains without the capability to fix N2 or to perform CCA of the group III type (CCA III); (2) strains which show both features; (3) strains with the ability to fix nitrogen, but that do not show any CCA III; and (4) strains that produce phycoerythrin, but without the capacity for CCA III or N2 -fixation. By examining the frequency distribution of isolates, these types were shown to prefer different habitats. While cyanobacterial strains capable of N2 -fixation, but without CCA III, were mainly obtained from stone crusts in the supralittoral zone, those with the potential for N2 -fixation as well as for CCA III were largely isolated from submersed macrophytes. Cyanobacteria that produce phycoerythrin, but do not perform CCA III or N2 -fixation, were found in the pelagic zone only. [source] Taxon-specific variation in the stable isotopic signatures (,13C and ,15N) of lake phytoplanktonFRESHWATER BIOLOGY, Issue 5 2006KRISTIINA VUORIO Summary 1. The variability in the stable isotope signatures of carbon and nitrogen (,13C and ,15N) in different phytoplankton taxa was studied in one mesotrophic and three eutrophic lakes in south-west Finland. The lakes were sampled on nine to 16 occasions over 2,4 years and most of the time were dominated by cyanobacteria and diatoms. A total of 151 taxon-specific subsamples covering 18 different phytoplankton taxa could be isolated by filtration through a series of sieves and by flotation/sedimentation, followed by microscopical identification and screening for purity. 2. Substantial and systematic differences between phytoplankton taxa, seasons and lakes were observed for both ,13C and ,15N. The values of ,13C ranged from ,34.4, to ,5.9, and were lowest in chrysophytes (,34.4, to ,31.3,) and diatoms (,30.6, to ,26.6,). Cyanobacteria were most variable (,32.4, to ,5.9,), including particularly high values in the nostocalean cyanobacterium Gloeotrichia echinulata (,14.4, to ,5.9,). For ,13C, the taxon-specific amplitude of temporal changes within a lake was usually <1,8, (<1,4, for microalgae alone and <1,8, for cyanobacteria alone), whereas the amplitude among taxa within a water sample was up to 31,. 3. The values of ,15N ranged from ,2.1, to 12.8, and were high in chrysophytes, dinophytes and diatoms, but low in the nitrogen-fixing cyanobacteria Anabaena spp., Aphanizomenon spp. and G. echinulata (,2.1, to 1.6,). Chroococcalean cyanobacteria ranged from ,1.4, to 8.9,. For ,15N, the taxon-specific amplitude of temporal changes within a lake was 2,6,, (2,6, for microalgae alone and 2,4, for cyanobacteria alone) and the amplitude among taxa within a water sample was up to 11,. 4. The isotopic signatures of phytoplankton changed systematically with their physical and chemical environment, most notably with the concentrations of nutrients, but correlations were non-systematic and site-specific. 5. The substantial variability in the isotopic signatures of phytoplankton among taxa, seasons and lakes complicates the interpretation of isotopic signatures in lacustrine food webs. However, taxon-specific values and seasonal patterns showed some consistency among years and may eventually be predictable. [source] Does high nitrogen loading prevent clear-water conditions in shallow lakes at moderately high phosphorus concentrations?FRESHWATER BIOLOGY, Issue 1 2005María A. González Sagrario Summary 1. The effect of total nitrogen (TN) and phosphorus (TP) loading on trophic structure and water clarity was studied during summer in 24 field enclosures fixed in, and kept open to, the sediment in a shallow lake. The experiment involved a control treatment and five treatments to which nutrients were added: (i) high phosphorus, (ii) moderate nitrogen, (iii) high nitrogen, (iv) high phosphorus and moderate nitrogen and (v) high phosphorus and high nitrogen. To reduce zooplankton grazers, 1+ fish (Perca fluviatilis L.) were stocked in all enclosures at a density of 3.7 individuals m,2. 2. With the addition of phosphorus, chlorophyll a and the total biovolume of phytoplankton rose significantly at moderate and high nitrogen. Cyanobacteria or chlorophytes dominated in all enclosures to which we added phosphorus as well as in the high nitrogen treatment, while cryptophytes dominated in the moderate nitrogen enclosures and the controls. 3. At the end of the experiment, the biomass of the submerged macrophytes Elodea canadensis and Potamogeton sp. was significantly lower in the dual treatments (TN, TP) than in single nutrient treatments and controls and the water clarity declined. The shift to a turbid state with low plant coverage occurred at TN >2 mg N L,1 and TP >0.13,0.2 mg P L,1. These results concur with a survey of Danish shallow lakes, showing that high macrophyte coverage occurred only when summer mean TN was below 2 mg N L,1, irrespective of the concentration of TP, which ranged between 0.03 and 1.2 mg P L,1. 4. Zooplankton biomass and the zooplankton : phytoplankton biomass ratio, and probably also the grazing pressure on phytoplankton, remained overall low in all treatments, reflecting the high fish abundance chosen for the experiment. We saw no response to nutrition addition in total zooplankton biomass, indicating that the loss of plants and a shift to the turbid state did not result from changes in zooplankton grazing. Shading by phytoplankton and periphyton was probably the key factor. 5. Nitrogen may play a far more important role than previously appreciated in the loss of submerged macrophytes at increased nutrient loading and for the delay in the re-establishment of the nutrient loading reduction. We cannot yet specify, however, a threshold value for N that would cause a shift to a turbid state as it may vary with fish density and climatic conditions. However, the focus should be widened to use control of both N and P in the restoration of eutrophic shallow lakes. [source] Do cyanobacteria dominate in eutrophic lakes because they fix atmospheric nitrogen?FRESHWATER BIOLOGY, Issue 6 2004L. R. Ferber Summary 1. The sources of nitrogen for phytoplankton were determined for a bloom-prone lake as a means of assessing the hypothesis that cyanobacteria dominate in eutrophic lakes because of their ability to fix nitrogen when the nitrogen : phosphorous (N : P) supply ratio is low and nitrogen a limiting resource. 2. Nitrogen fixation rates, estimated through acetylene reduction with 15N calibration, were compared with 15N-tracer estimates of ammonium and nitrate uptake monthly during the ice-free season of 1999. In addition, the natural N stable isotope composition of phytoplankton, nitrate and ammonium were measured biweekly and the contribution of N2 to the phytoplankton signature estimated with a mixing model. 3. Although cyanobacteria made up 81,98% of phytoplankton biomass during summer and autumn, both assays suggested minimal N acquisition through fixation (<9% for the in-situ incubations; <2% for stable isotope analysis). Phytoplankton acquired N primarily as ammonium (82,98%), and secondarily as nitrate (15,18% in spring and autumn, but <5% in summer). Heterocyst densities of <3 per 100 fixer cells confirmed low reliance on fixation. 4. The lake showed symptoms of both light and nitrogen limitation. Cyanobacteria may have dominated by monopolizing benthic sources of ammonium, or by forming surface scums that shaded other algae. [source] Aminopeptidase and phosphatase activities in basins of Lake Hiidenvesi dominated by cyanobacteria and in laboratory grown AnabaenaFRESHWATER BIOLOGY, Issue 9 2002JAANA VAITOMAA 1.,Extracellular enzyme activities were examined in freshwater basins representing a transition from hypertrophy to mesotrophy and in axenic cyanobacterial cultures to evaluate the ecological role of extracellular enzyme activities of cyanobacteria. 2.,Aminopeptidase activity was related to the trophic status of the lake basins. The activity was highest in the most eutrophic basin and decreased in the less nutrient-rich basins. Cyanobacteria were the most important autotrophic organisms and aminopeptidase activity was positively associated with cyanobacterial biomass. 3.,In an axenic Anabaena batch culture, nitrogenase activity was several orders of magnitude higher than leucine aminopeptidase activity. Nitrate did not have an effect on aminopeptidase activity or growth, but significantly reduced the rate of nitrogen fixation. A high phosphorus concentration at the beginning of the Anabaena batch-culture experiment resulted in reduced phosphatase activity. 4.,In Lake Hiidenvesi, aminopeptidase activity probably originated mostly from attached bacteria and less so from cyanobacteria. [source] Earliest fossil record of bacterial,cyanobacterial mat consortia: the early Silurian Passage Creek biota (440 Ma, Virginia, USA)GEOBIOLOGY, Issue 2 2008A. M. F. TOMESCU ABSTRACT Cyanobacteria in terrestrial and aquatic habitats are frequently associated with heterotrophic bacteria, and such associations are most often metabolically interactive. Functionally, the members of such bacterial,cyanobacterial consortia benefit from diverse metabolic capabilities of their associates, thus exceeding the sum of their parts. Such associations may have been just as ubiquitous in the past, but the fossil record has not produced any direct evidence for such associations to date. In this paper, we document fossil bacteria associated with a macrophytic cyanobacterial mat in the early Silurian (Llandovery) Massanutten Sandstone of Virginia, USA. Both the bacterial and the cyanobacterial cells are preserved by mineral replacement (pyrite subsequently replaced by iron oxyhydroxides) within an amorphous carbonaceous matrix which represents the common exopolysaccharide investment of the cyanobacterial colony. The bacteria are rod-shaped, over 370 nm long and 100 nm in diameter, and occur both as isolated cells and as short filaments. This occurrence represents the oldest fossil evidence for bacterial,cyanobacterial associations, documenting that such consortia were present 440 Ma ago, and revealing the potential for them to be recognized deeper in the fossil record. 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