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1.
FEMS Microbiol Ecol ; 96(2)2020 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-31905236

RESUMO

Ecological communities are regulated by the flow of energy through environments. Energy flow is typically limited by access to photosynthetically active radiation (PAR) and oxygen concentration (O2). The microbial mats growing on the bottom of Lake Fryxell, Antarctica, have well-defined environmental gradients in PAR and (O2). We analyzed the metagenomes of layers from these microbial mats to test the extent to which access to oxygen and light controls community structure. We found variation in the diversity and relative abundances of Archaea, Bacteria and Eukaryotes across three (O2) and PAR conditions: high (O2) and maximum PAR, variable (O2) with lower maximum PAR, and low (O2) and maximum PAR. We found distinct communities structured by the optimization of energy use on a millimeter-scale across these conditions. In mat layers where (O2) was saturated, PAR structured the community. In contrast, (O2) positively correlated with diversity and affected the distribution of dominant populations across the three habitats, suggesting that meter-scale diversity is structured by energy availability. Microbial communities changed across covarying gradients of PAR and (O2). The comprehensive metagenomic analysis suggests that the benthic microbial communities in Lake Fryxell are structured by energy flow across both meter- and millimeter-scales.

2.
Environ Microbiol ; 22(1): 59-75, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31599093

RESUMO

Large skeleton specimens are often featured as iconic open displays in Natural History Museums, for example, the blue whale 'Hope' at the Natural History Museum, London. A study on Hope's bone surface was performed to assess the biodeterioration potential of fungi. Fungi were isolated, and a fungal internal transcribed spacer (ITS) clone library survey was performed on dust and bone material. Mineral particles derived from bone and dust were analysed using energy dispersive X-ray spectroscopy, variable pressure scanning electron microscopy (SEM) and high vacuum SEM. Results showed that bone material, although mainly mineral in nature, and therefore less susceptible than organic materials to biodeterioration phenomena in the indoor environments, offers niches for specialized fungi and is affected by unusual and yet not so well-documented mechanisms of alteration. Areas of bone surface were covered with a dense biofilm mostly composed of fungal hyphae, which produced tunnelling and extensive deposition of calcium and iron-containing secondary minerals. Airborne halophilic and xerophilic fungi including taxa grouping into Ascomycota and Basidiomycota, capable of displacing salts and overcome little water availability, were found to dominate the microbiome of the bone surface.

3.
Geobiology ; 17(5): 551-563, 2019 09.
Artigo em Inglês | MEDLINE | ID: mdl-31325234

RESUMO

Bacteriohopanepolyols (BHPs) are pentacyclic triterpenoid lipids that contribute to the structural integrity and physiology of some bacteria. Because some BHPs originate from specific classes of bacteria, BHPs have potential as taxonomically and environmentally diagnostic biomarkers. For example, a stereoisomer of bacteriohopanetetrol (informally BHT II) has been associated with anaerobic ammonium oxidation (anammox) bacteria and suboxic to anoxic marine environments where anammox is active. As a result, the detection of BHT II in the sedimentary record and fluctuations in the relative abundance of BHT II may inform reconstructions of nitrogen cycling and ocean redox changes through the geological record. However, there are uncertainties concerning the sources of BHT II and whether or not BHT II is produced in abundance in non-marine environments, both of which are pertinent to interpretations of BHT II signatures in sediments. To address these questions, we investigate the BHP composition of benthic microbial mats from Lake Fryxell, Antarctica. Lake Fryxell is a perennially ice-covered lake with a sharp oxycline in a density-stabilized water column. We describe the diversity and abundance of BHPs in benthic microbial mats across a transect from oxic to anoxic conditions. Generally, BHP abundances and diversity vary with the morphologies of microbial mats, which were previously shown to reflect local environmental conditions, such as irradiance and oxygen and sulfide concentrations. BHT II was identified in mats that exist within oxic to anoxic portions of the lake. However, anammox bacteria have yet to be identified in Lake Fryxell. We examine our results in the context of BHPs as biomarkers in modern and ancient environments.


Assuntos
Bactérias/metabolismo , Sedimentos Geológicos/análise , Lipídeos/análise , Triterpenos Pentacíclicos/análise , Regiões Antárticas , Bactérias/química , Fenômenos Fisiológicos Bacterianos , Lagos/química , Polímeros/análise
4.
Proc Biol Sci ; 284(1857)2017 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-28637848

RESUMO

Evidence of climate-driven environmental change is increasing in Antarctica, and with it comes concern that this will propagate to impacts on biological communities. Recognition and prediction of change needs to incorporate the extent and timescales over which communities vary under extant conditions. However, few observations of Antarctic microbial communities, which dominate inland habitats, allow this. We therefore carried out the first molecular comparison of Cyanobacteria in historic herbarium microbial mats from freshwater ecosystems on Ross Island and the McMurdo Ice Shelf, collected by Captain R.F. Scott's 'Discovery' Expedition (1902-1903), with modern samples from those areas. Using 16S rRNA gene surveys, we found that modern and historic cyanobacteria assemblages showed some variation in community structure but were dominated by the same genotypes. Modern communities had a higher richness, including genotypes not found in historic samples, but they had the highest similarity to other cyanobacteria sequences from Antarctica. The results imply slow cyanobacterial 16S rRNA gene genotype turnover and considerable community stability within Antarctic microbial mats. We suggest that this relates to Antarctic freshwater 'organisms requiring a capacity to withstand diverse stresses, and that this could also provide a degree of resistance and resilience to future climatic-driven environmental change in Antarctica.


Assuntos
Biodiversidade , Cianobactérias/classificação , Regiões Antárticas , Ecossistema , Filogenia , RNA Ribossômico 16S/genética
5.
Nat Commun ; 8: 14499, 2017 02 15.
Artigo em Inglês | MEDLINE | ID: mdl-28198359

RESUMO

Iron supplied by glacial weathering results in pronounced hotspots of biological production in an otherwise iron-limited Southern Ocean Ecosystem. However, glacial iron inputs are thought to be dominated by icebergs. Here we show that surface runoff from three island groups of the maritime Antarctic exports more filterable (<0.45 µm) iron (6-81 kg km-2 a-1) than icebergs (0.0-1.2 kg km-2 a-1). Glacier-fed streams also export more acid-soluble iron (27.0-18,500 kg km-2 a-1) associated with suspended sediment than icebergs (0-241 kg km-2 a-1). Significant fluxes of filterable and sediment-derived iron (1-10 Gg a-1 and 100-1,000 Gg a-1, respectively) are therefore likely to be delivered by runoff from the Antarctic continent. Although estuarine removal processes will greatly reduce their availability to coastal ecosystems, our results clearly indicate that riverine iron fluxes need to be accounted for as the volume of Antarctic melt increases in response to 21st century climate change.


Assuntos
Ecossistema , Ferro/química , Água do Mar/química , Regiões Antárticas , Geografia , Sedimentos Geológicos/química , Ilhas , Rios , Estações do Ano , Solubilidade , Água/química
6.
FEMS Microbiol Ecol ; 92(6): fiw080, 2016 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-27090760

RESUMO

The interface between biological and geochemical components in the surface crust of a saline soil was investigated using X-ray diffraction, and variable pressure scanning electron microscopy in combination with energy dispersive X-ray spectrometry. Mineral compounds such as halite and gypsum were identified crystallized around filaments of cyanobacteria. A total of 92 genera were identified from the bacterial community based on 16S gene pyrosequencing analysis. The occurrence of the gypsum crystals, their shapes and compartmentalization suggested that they separated NaCl from the immediate microenvironment of the cyanobacteria, and that some cyanobacteria and communities of sulfur bacteria may had a physical control over the distinctive halite and gypsum structures produced. This suggests that cyanobacteria might directly or indirectly promote the formation of a protective envelope made of calcium and sulfur-based compounds.


Assuntos
Sulfato de Cálcio/metabolismo , Cianobactérias/metabolismo , Cloreto de Sódio/metabolismo , Solo/química , Compostos de Enxofre/metabolismo , Cianobactérias/genética , Microscopia Eletrônica de Varredura , RNA Ribossômico 16S/genética , Microbiologia do Solo , Difração de Raios X
7.
Appl Environ Microbiol ; 82(2): 620-30, 2016 01 15.
Artigo em Inglês | MEDLINE | ID: mdl-26567300

RESUMO

Lake Fryxell is a perennially ice-covered lake in the McMurdo Dry Valleys, Antarctica, with a sharp oxycline in a water column that is density stabilized by a gradient in salt concentration. Dissolved oxygen falls from 20 mg liter(-1) to undetectable over one vertical meter from 8.9- to 9.9-m depth. We provide the first description of the benthic mat community that falls within this oxygen gradient on the sloping floor of the lake, using a combination of micro- and macroscopic morphological descriptions, pigment analysis, and 16S rRNA gene bacterial community analysis. Our work focused on three macroscopic mat morphologies that were associated with different parts of the oxygen gradient: (i) "cuspate pinnacles" in the upper hyperoxic zone, which displayed complex topography and were dominated by phycoerythrin-rich cyanobacteria attributable to the genus Leptolyngbya and a diverse but sparse assemblage of pennate diatoms; (ii) a less topographically complex "ridge-pit" mat located immediately above the oxic-anoxic transition containing Leptolyngbya and an increasing abundance of diatoms; and (iii) flat prostrate mats in the upper anoxic zone, dominated by a green cyanobacterium phylogenetically identified as Phormidium pseudopriestleyi and a single diatom, Diadesmis contenta. Zonation of bacteria was by lake depth and by depth into individual mats. Deeper mats had higher abundances of bacteriochlorophylls and anoxygenic phototrophs, including Chlorobi and Chloroflexi. This suggests that microbial communities form assemblages specific to niche-like locations. Mat morphologies, underpinned by cyanobacterial and diatom composition, are the result of local habitat conditions likely defined by irradiance and oxygen and sulfide concentrations.


Assuntos
Bactérias/isolamento & purificação , Camada de Gelo/microbiologia , Lagos/microbiologia , Oxigênio/análise , Regiões Antárticas , Bactérias/classificação , Bactérias/genética , Bactérias/metabolismo , Biodiversidade , Camada de Gelo/química , Lagos/análise , Dados de Sequência Molecular , Filogenia
8.
FEMS Microbiol Ecol ; 91(12)2015 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26572547

RESUMO

Closed cryoconite holes (CCHs) are small aquatic ecosystems enclosed in glacier surface ice, and they collectively contribute substantial aquatic habitat to inland Antarctica. We examined the morphology, geochemistry and bacterial diversity of 57 CCHs, spread over seven sites, located on five glaciers, covering a range of latitudes, elevations and distance from open seawater. Isotopes confirmed glacial ice as the initial water source, with water chemistry evolving through freeze concentration and photosynthetic processes to have conductivities ranging from <0.005 to >4 mS cm(-1) and pH from <5 to >11. Nitrate concentrations were more elevated in inland, higher altitude sites. Bacterial communities were characterized by Automated Ribosomal Intergenic Spacer Analysis and high-throughput sequencing. The dominant phyla were Cyanobacteria, Bacteroides, Proteobacteria and Actinobacteria. CCH bacterial communities predominantly grouped by geographic location, suggesting initial wind-borne inocula from local and regional sources play a role in structuring assemblages. However, multivariate multiple regression analysis indicated that internal CCH conditions also influenced community structure, particularly the ion content and pH of the liquid water. This highlights the importance of founder bacterial populations, isolation and water chemistry in the evolution of CCH bacterial communities.


Assuntos
Bactérias/classificação , Camada de Gelo/microbiologia , Água do Mar/química , Água do Mar/microbiologia , Microbiologia da Água , Actinobacteria/classificação , Actinobacteria/isolamento & purificação , Regiões Antárticas , Bactérias/isolamento & purificação , Bacteroides/classificação , Bacteroides/isolamento & purificação , Biodiversidade , Cianobactérias/classificação , Cianobactérias/isolamento & purificação , Ecossistema , Geografia , Proteobactérias/classificação , Proteobactérias/isolamento & purificação
9.
Biology (Basel) ; 2(1): 151-76, 2013 Jan 25.
Artigo em Inglês | MEDLINE | ID: mdl-24832656

RESUMO

Lake Vanda is a perennially ice-covered, closed-basin lake in the McMurdo Dry Valleys, Antarctica. Laminated photosynthetic microbial mats cover the floor of the lake from below the ice cover to >40 m depth. In recent decades, the water level of Lake Vanda has been rising, creating a "natural experiment" on development of mat communities on newly flooded substrates and the response of deeper mats to declining irradiance. Mats in recently flooded depths accumulate one lamina (~0.3 mm) per year and accrue ~0.18 µg chlorophyll-a cm-2 y-1. As they increase in thickness, vertical zonation becomes evident, with the upper 2-4 laminae forming an orange-brown zone, rich in myxoxanthophyll and dominated by intertwined Leptolyngbya trichomes. Below this, up to six phycobilin-rich green/pink-pigmented laminae form a subsurface zone, inhabited by Leptolyngbya, Oscillatoria and Phormidium morphotypes. Laminae continued to increase in thickness for several years after burial, and PAM fluorometry indicated photosynthetic potential in all pigmented laminae. At depths that have been submerged for >40 years, mats showed similar internal zonation and formed complex pinnacle structures that were only beginning to appear in shallower mats. Chlorophyll-a did not change over time and these mats appear to represent resource-limited "climax" communities. Acclimation of microbial mats to changing environmental conditions is a slow process, and our data show how legacy effects of past change persist into the modern community structure.

10.
FEMS Microbiol Ecol ; 82(2): 416-28, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22630054

RESUMO

Cyanobacterial mats are commonly found in freshwater ecosystems throughout the polar regions. Most mats are multilayered three-dimensional structures with the filamentous cyanobacteria embedded in a gel-like matrix. Although early descriptions mentioned the presence of larger organisms including metazoans living in the mats, there have been few studies specifically focused on the microbial eukaryotes, which are often small cells with few morphological features suitable for identification by microscopy. Here, we applied 18S rRNA gene clone library analysis to identify eukaryotes in cyanobacterial mat communities from both the Antarctic and the extreme High Arctic. We identified 39 ribotypes at the level of 99% sequence similarity. These consisted of taxa within algal and other protist groups including Chlorophyceae, Prasinophyceae, Ulvophyceae, Trebouxiophyceae, Bacillariophyceae, Chrysophyceae, Ciliophora, and Cercozoa. Fungi were also recovered, as were 21 metazoan ribotypes. The eukaryotic taxa appeared habitat-specific with little overlap between lake, pond, and ice shelf communities. Some ribotypes were common to both Arctic and Antarctic mats, suggesting global dispersal of these taxa and similarity in the environmental filters acting on protist communities. Many of these eukaryotic taxa likely benefit from protected, nutrient-rich microhabitats within the cyanobacterial mat environment.


Assuntos
Ecossistema , Eucariotos/isolamento & purificação , Água Doce/microbiologia , Regiões Antárticas , Regiões Árticas , Cianobactérias/crescimento & desenvolvimento , Eucariotos/classificação , Eucariotos/genética , Biblioteca Gênica , Gelo/análise , Filogenia , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 18S/genética , Ribotipagem
11.
FEMS Microbiol Ecol ; 82(2): 356-66, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22486587

RESUMO

The Pyramid Trough (Lat 78°S) has recently gained protection under the Antarctic Treaty system, owing to its wetland values. Here, we describe the microbial diversity of this system, with emphasis on cyanobacteria, and evaluate environment-biota relationships. Geochemistry separates ponds along hydrological gradients receiving recent inflows of dilute meltwater, from a second group that is rarely inundated and where chemistry is dominated by evaporation. Cyanobacteria-based microbial mats dominated the biota throughout. Mats were characterized by light-microscopy, pigment analysis, automated ribosomal intergenic spacer analysis and 16S rRNA gene clone libraries. A total of 17 morphotypes and 21 ribotypes were identified, mostly Oscillatoriales and several taxa that are usually rare in continental Antarctica, including Chroococcales and scytomin-rich Calothrix/Dichothrix, were abundant. There was a general decline in cyanobacterial diversity with increasing conductivity, but weak support for either differences in community composition between the two groups of ponds or sorting of taxa along the hydrological gradients with the pond groups. This implies a broad environmental tolerance and a prevalence of neutral assembly mechanisms in cyanobacterial communities of Antarctic wetland ecosystems.


Assuntos
Biodiversidade , Cianobactérias/classificação , Microbiologia da Água , Áreas Alagadas , Regiões Antárticas , Biota , Cianobactérias/genética , DNA Bacteriano/genética , DNA Espaçador Ribossômico/genética , Biblioteca Gênica , Genes de RNAr , Filogenia , Polimorfismo de Fragmento de Restrição , RNA Ribossômico 16S/genética , Ribotipagem
12.
Appl Environ Microbiol ; 78(2): 549-59, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22081564

RESUMO

Polar and alpine microbial communities experience a variety of environmental stresses, including perennial cold and freezing; however, knowledge of genomic responses to such conditions is still rudimentary. We analyzed the metagenomes of cyanobacterial mats from Arctic and Antarctic ice shelves, using high-throughput pyrosequencing to test the hypotheses that consortia from these extreme polar habitats were similar in terms of major phyla and subphyla and consequently in their potential responses to environmental stresses. Statistical comparisons of the protein-coding genes showed similarities between the mats from the two poles, with the majority of genes derived from Proteobacteria and Cyanobacteria; however, the relative proportions differed, with cyanobacterial genes more prevalent in the Antarctic mat metagenome. Other differences included a higher representation of Actinobacteria and Alphaproteobacteria in the Arctic metagenomes, which may reflect the greater access to diasporas from both adjacent ice-free lands and the open ocean. Genes coding for functional responses to environmental stress (exopolysaccharides, cold shock proteins, and membrane modifications) were found in all of the metagenomes. However, in keeping with the greater exposure of the Arctic to long-range pollutants, sequences assigned to copper homeostasis genes were statistically (30%) more abundant in the Arctic samples. In contrast, more reads matching the sigma B genes were identified in the Antarctic mat, likely reflecting the more severe osmotic stress during freeze-up of the Antarctic ponds. This study underscores the presence of diverse mechanisms of adaptation to cold and other stresses in polar mats, consistent with the proportional representation of major bacterial groups.


Assuntos
Bactérias/classificação , Bactérias/genética , Biota , Sedimentos Geológicos/microbiologia , Metagenoma , Regiões Antárticas , Regiões Árticas , Análise de Sequência de DNA
13.
Appl Environ Microbiol ; 77(10): 3234-43, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21460114

RESUMO

We applied molecular, microscopic, and culture techniques to characterize the microbial communities in snow and air at remote sites in the Canadian High Arctic (Ward Hunt Island, Ellesmere Island, and Cornwallis Island, latitudes 74 to 83(o)N). Members of the Bacteria and Eukarya were prevalent in the snow, and their small subunit (SSU) rRNA gene signatures indicated strong local aerial transport within the region over the preceding 8 months of winter snowpack accumulation. Many of the operational taxonomic units (OTUs) were similar to previously reported SSU rRNA gene sequences from the Arctic Ocean, suggesting the importance of local aerial transport processes for marine microbiota. More than 47% of the cyanobacterial OTUs in the snow have been previously found in microbial mats in the region, indicating that this group was also substantially derived from local sources. Viable cyanobacteria isolated from the snow indicated free exchange between the snow and adjacent mat communities. Other sequences were most similar to those found outside the Canadian Arctic but were from snow, lake and sea ice, glaciers and permafrost, alpine regions, Antarctica, and other regions of the Arctic, supporting the concept of global distribution of microbial ecotypes throughout the cold biosphere.


Assuntos
Microbiologia do Ar , Ar/parasitologia , Cianobactérias/isolamento & purificação , Eucariotos/isolamento & purificação , Neve/microbiologia , Neve/parasitologia , Regiões Árticas , Análise por Conglomerados , Temperatura Baixa , Cianobactérias/classificação , Cianobactérias/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Eucariotos/classificação , Eucariotos/genética , Dados de Sequência Molecular , Filogenia , Análise de Sequência de DNA
14.
ISME J ; 4(2): 191-202, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19890368

RESUMO

Perennially cold habitats are diminishing as a result of climate change; however, little is known of the diversity or biogeography of microbes that thrive in such environments. Here we use targeted 16S rRNA gene surveys to evaluate the global affinities of cold-dwelling cyanobacteria from lake, stream and ice communities living at the northern limit of High Arctic Canada. Pigment signature analysis by HPLC confirmed the dominance of cyanobacteria in the phototrophic communities of these High Arctic microbial mats, with associated populations of chlorophytes and chromophytes. Microscopic analysis of the cyanobacteria revealed a diverse assemblage of morphospecies grouping into orders Oscillatoriales, Nostocales and Chroococcales. The 16S rRNA gene sequences from six clone libraries grouped into a total of 24 ribotypes, with a diversity in each mat ranging from five ribotypes in ice-based communities to 14 in land-based pond communities. However, no significant differences in composition were observed between these two microbial mat systems. Based on clone-library and phylogenetic analysis, several of the High Arctic ribotypes were found to be >99% similar to Antarctic and alpine sequences, including to taxa previously considered endemic to Antarctica. Among the latter, one High Arctic sequence was found 99.8% similar to Leptolyngbya antarctica sequenced from the Larsemann Hills, Antarctica. More than 68% of all identified ribotypes at each site matched only cyanobacterial sequences from perennially cold terrestrial ecosystems, and were <97.5% similar to sequences from warmer environments. These results imply the global distribution of low-temperature cyanobacterial ecotypes throughout the cold terrestrial biosphere.


Assuntos
Cianobactérias/classificação , Microbiologia da Água , Regiões Antárticas , Regiões Árticas , Biodiversidade , Canadá , Mudança Climática , Temperatura Baixa , Cianobactérias/química , Cianobactérias/genética , Cianobactérias/fisiologia , DNA Bacteriano/genética , Ecossistema , Filogenia , Pigmentos Biológicos/análise , RNA Ribossômico 16S/genética
15.
Water Res ; 41(2): 492-8, 2007 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-17126876

RESUMO

Cyanobacteria that produce the toxin microcystin have been isolated from many parts of the world. Most of these organisms are planktonic; however, we report on several microcystin-producing benthic filamentous cyanobacterial isolates from four drinking-water reservoirs in southern California (USA): Lake Mathews, Lake Skinner, Diamond Valley Lake (DVL), and Lake Perris. Some samples of benthic material from these reservoirs tested positive for microcystin by an ELISA tube assay, and all the positive samples had in common a green filamentous cyanobacterium 10-15microm in diameter. Seventeen unialgal strains of the organism were isolated and tested positive by ELISA, and 11 cultures of these strains were found to contain high concentrations of microcystin-LR (90-432microgL(-1)). The cultures were analyzed by protein phosphatase inhibition assay (PPIA) and HPLC with photodiode array detector (PDA) or liquid chromatography/mass spectrometry (LC/MS). Microcystin per unit carbon was determined for six cultures and ranged from 1.15 to 4.15microgmg(-1) C. Phylogenetic analysis of four cultures from Lake Skinner and DVL using cyanobacterial-specific PCR and sequencing of the partial 16S rRNA gene suggested the highest similarity to an unidentified cyanobacterium in the oscillatoriales, and to a Phormidium sp. Morphologically, some of the isolates were similar to Oscillatoria, and others resembled Lyngbya. The significance of these organisms lies in the relative scarcity of known toxin producers among freshwater benthic cyanobacteria, and also as a source of cell-bound microcystin in these reservoirs.


Assuntos
Cianobactérias/metabolismo , Sedimentos Geológicos/microbiologia , Microcistinas/metabolismo , Plâncton/metabolismo , Abastecimento de Água/análise , California , Cianobactérias/classificação , Cianobactérias/isolamento & purificação , Monitoramento Ambiental , Filogenia , Plâncton/classificação , Plâncton/isolamento & purificação
16.
Toxicon ; 47(3): 271-8, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16386280

RESUMO

Cyanobacteria are well known for their production of non-ribosomal cyclic peptide toxins, including microcystin, in temperate and tropical regions, however, the production of these compounds in extremely cold environments is still largely unexplored. Therefore, we investigated the production of protein phosphatase inhibiting microcystins by Antarctic cyanobacteria. We have identified microcystin-LR and for the first time [D-Asp3] microcystin-LR by mass spectrometric analysis in Antarctic cyanobacteria. The microcystins were extracted from a benthic microbial community that was sampled from a meltwater pond (Fresh Pond, McMurdo Ice Shelf, Antarctica). The extracted cyanobacterial cyclic peptides were equivalent to 11.4 ng MC-LR per mg dry weight by semi-quantitative analyses using HPLC-DAD and the protein phosphatase inhibition assay. Furthermore, we were able to identify the presence of cyanobacterial non-ribosomal peptide synthetase (NRPS) and polyketide synthase (PKS) genes in total DNA extracts from the mat community.


Assuntos
Toxinas Bacterianas/biossíntese , Biomassa , Cianobactérias/metabolismo , Peptídeos Cíclicos/biossíntese , Animais , Regiões Antárticas , Toxinas Bacterianas/química , Toxinas Bacterianas/toxicidade , Cromatografia Líquida de Alta Pressão , DNA Bacteriano/química , Água Doce , Microcistinas , Peptídeos Cíclicos/química , Peptídeos Cíclicos/toxicidade , Fosfoproteínas Fosfatases/antagonistas & inibidores , Reação em Cadeia da Polimerase
17.
Arch Microbiol ; 185(2): 107-14, 2006 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-16402223

RESUMO

The cyanobacterial hepatotoxins, microcystin and nodularin, are produced by a wide range of cyanobacteria. Microcystin production has been reported in the four cyanobacterial orders: Oscillatoriales, Chroococcales, Stigonematales, and Nostocales. The production of nodularin is a distinct characteristic of the Nostocales genus Nodularia. A single rapid method is needed to reliably detect cyanobacteria that are potentially capable of producing these hepatotoxins. To this end, a PCR was designed to detect all potential microcystin and nodularin-producing cyanobacteria from laboratory cultures as well as in harmful algal blooms. The aminotransferase (AMT) domain, which is located on the modules mcyE and ndaF of the microcystin and nodularin synthetase enzyme complexes, respectively, was chosen as the target sequence because of its essential function in the synthesis of all microcystins as well as nodularins. Using the described PCR, it was possible to amplify a 472 bp PCR product from the AMT domains of all tested hepatotoxic species and bloom samples. Sequence data provided further insight into the evolution of the microcystin and nodularin synthetases through bioinformatic analyses of the AMT in microcystin and nodularin synthetases, with congruence between the evolution of 16S rRNA and the AMT domain.


Assuntos
Proteínas de Bactérias/genética , Toxinas Bacterianas/genética , Cianobactérias/genética , Evolução Molecular , Peptídeo Sintases/genética , Proteínas de Bactérias/metabolismo , Toxinas Bacterianas/metabolismo , Sequência de Bases , Cianobactérias/classificação , Cianobactérias/metabolismo , DNA Bacteriano/química , DNA Bacteriano/genética , Microcistinas/metabolismo , Dados de Sequência Molecular , Peptídeo Sintases/metabolismo , Peptídeos Cíclicos/metabolismo , Filogenia , Análise de Sequência de DNA , Homologia de Sequência do Ácido Nucleico
18.
Environ Microbiol ; 7(4): 519-29, 2005 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15816929

RESUMO

This study investigated the diversity of cyanobacterial mat communities of three meltwater ponds--Fresh, Orange and Salt Ponds, south of Bratina Island, McMurdo Ice Shelf, Antarctica. A combined morphological and genetic approach using clone libraries was used to investigate the influence of salinity on cyanobacterial diversity within these ecosystems without prior cultivation or isolation of cyanobacteria. We were able to identify 22 phylotypes belonging to Phormidium sp., Oscillatoria sp. and Lyngbya sp. In addition, we identified Antarctic Nostoc sp., Nodularia sp. and Anabaena sp. from the clone libraries. Fresh (17 phylotypes) and Orange (nine phylotypes) Ponds showed a similar diversity in contrast to that of the hypersaline Salt Pond (five phylotypes), where the diversity within cyanobacterial mats was reduced. Using the comparison of identified phylotypes with existing Antarctic sequence data, it was possible to gain further insight into the different levels of distribution of phylotypes identified in the investigated cyanobacterial mat communities of McMurdo Ice Shelf.


Assuntos
Biodiversidade , Cianobactérias/classificação , Cianobactérias/isolamento & purificação , Microbiologia da Água , Regiões Antárticas , Clonagem Molecular , Cianobactérias/genética , Cianobactérias/fisiologia , DNA Bacteriano/química , DNA Bacteriano/genética , DNA Bacteriano/isolamento & purificação , Dados de Sequência Molecular , Filogenia , Análise de Sequência de DNA
19.
FEMS Microbiol Lett ; 243(1): 293-301, 2005 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-15668032

RESUMO

The cyanobacterial communities associated with stromatolites surviving in extreme habitats are a potentially rich source of bioactive secondary metabolites. We screened for the potential for production of bioactive metabolites in diverse species of cyanobacteria isolated from stromatolites in Hamelin Pool, Shark Bay, Australia. Using degenerate primer sets, putative peptide synthetase and polyketide synthase genes were detected from strains of Symploca, Leptolyngybya, Microcoleus, Pleuorocapsa, and Plectonema sp. Sequence analysis indicates the enzymes encoded by these genes may be responsible for the production of different secondary metabolites, such as hepatotoxins and antibiotics. Computer modelling was also conducted to predict the putative amino acid recognised by the unknown adenylation domain in the NRPS sequences. Mass spectral analysis also allowed the putative identification of the cyclic peptides cyanopeptolin S and 21-bromo-oscillatoxin A in two of the isolates. This is the first time evidence of secondary metabolite production has been shown in stromatolite-associated microorganisms.


Assuntos
Antibacterianos/metabolismo , Toxinas Bacterianas/metabolismo , Cianobactérias/enzimologia , Cianobactérias/genética , Sedimentos Geológicos/microbiologia , Água do Mar/microbiologia , Austrália , Cianobactérias/crescimento & desenvolvimento , Cianobactérias/isolamento & purificação , Ecossistema , Sedimentos Geológicos/química , Dados de Sequência Molecular , Peptídeo Sintases/genética , Peptídeo Sintases/metabolismo , Filogenia , Policetídeo Sintases/genética , Policetídeo Sintases/metabolismo , Reação em Cadeia da Polimerase , Análise de Sequência de DNA , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
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