共查询到20条相似文献,搜索用时 31 毫秒
1.
Nuraan Khan Marla Tuffin William Stafford Craig Cary Donnabella C. Lacap Stephen B. Pointing Don Cowan 《Polar Biology》2011,34(11):1657-1668
The McMurdo Dry Valleys region of eastern Antarctica is a cold desert that presents extreme challenges to life. Hypolithic
microbial colonisation of the subsoil surfaces of translucent quartz rocks represent a significant source of terrestrial biomass
and productivity in this region. Previous studies have described hypoliths as dominated by cyanobacteria. However, hypoliths
that occur in the lower Dry Valleys such as the Miers, Garwood and Marshall Valleys are unusual as they are not necessarily
cyanobacteria-dominated. These hypoliths support significant eukaryal colonisation by fungi and mosses in addition to cyanobacteria-dominated
bacterial assemblages and so have considerable ecological value in this barren landscape. Here, we characterise these novel
hypoliths by analysis of environmental rRNA gene sequences. The hypolithic community was demonstrated to be distinct from
the surrounding soil and non-translucent rocks. Hypoliths supported cyanobacterial signatures from the Oscillatoriales and
Nostocales. Other heterotrophic bacterial signatures were also recovered, and these were phylogenetically diverse and spanned
8 other bacterial phyla. Archaeal phylotypes recovered were phylogenetically affiliated with the large group of unclassified,
uncultured Crenarcheota. Eukaryal phylotypes indicated that free-living ascomycetous fungi, chlorophytes and mosses (Bryum sp.) were all supported by these hypoliths, and these are thought to be responsible for the extensive eukaryotic biomass
that develops around quartz rocks. 相似文献
2.
Y Chan DC Lacap MC Lau KY Ha KA Warren-Rhodes CS Cockell DA Cowan CP McKay SB Pointing 《Environmental microbiology》2012,14(9):2272-2282
Drylands are the largest terrestrial biome on Earth and a ubiquitous feature is desert pavement terrain, comprising rocks embedded in the mineral soil surface. Quartz and other translucent rocks are common and microbial communities termed hypoliths develop as biofilms on their ventral surfaces. In extreme deserts these represent major concentrations of biomass, and are emerging as key to geobiological processes and soil stabilization. These highly specialized communities are dominated by cyanobacteria that support diverse heterotrophic assemblages. Here we identify global-scale trends in the ecology of hypoliths that are strongly related to climate, particularly with regard to shifts in cyanobacterial assemblages. A synthesis of available data revealed a linear trend for colonization with regard to climate, and we suggest potential application for hypoliths as 'biomarkers' of aridity on a landscape scale. The potential to exploit the soil-stabilizing properties of hypolithic colonization in environmental engineering on dryland soils is also discussed. 相似文献
3.
Charmaine C. M. Yung Yuki Chan Donnabella C. Lacap Sergio Pérez-Ortega Asuncion de los Rios-Murillo Charles K. Lee S. Craig Cary Stephen B. Pointing 《Microbial ecology》2014,68(2):351-359
The Antarctic Dry Valleys are unable to support higher plant and animal life and so microbial communities dominate biotic ecosystem processes. Soil communities are well characterized, but rocky surfaces have also emerged as a significant microbial habitat. Here, we identify extensive colonization of weathered granite on a landscape scale by chasmoendolithic microbial communities. A transect across north-facing and south-facing slopes plus valley floor moraines revealed 30–100 % of available substrate was colonized up to an altitude of 800 m. Communities were assessed at a multidomain level and were clearly distinct from those in surrounding soils and other rock-inhabiting cryptoendolithic and hypolithic communities. All colonized rocks were dominated by the cyanobacterial genus Leptolyngbya (Oscillatoriales), with heterotrophic bacteria, archaea, algae, and fungi also identified. Striking patterns in community distribution were evident with regard to microclimate as determined by aspect. Notably, a shift in cyanobacterial assemblages from Chroococcidiopsis-like phylotypes (Pleurocapsales) on colder–drier slopes, to Synechococcus-like phylotypes (Chroococcales) on warmer–wetter slopes. Greater relative abundance of known desiccation-tolerant bacterial taxa occurred on colder–drier slopes. Archaeal phylotypes indicated halotolerant taxa and also taxa possibly derived from nearby volcanic sources. Among the eukaryotes, the lichen photobiont Trebouxia (Chlorophyta) was ubiquitous, but known lichen-forming fungi were not recovered. Instead, fungal assemblages were dominated by ascomycetous yeasts. We conclude that chasmoendoliths likely constitute a significant geobiological phenomenon at lower elevations in granite-dominated Antarctic Dry Valley systems. 相似文献
4.
Smail Mehda M. Ángeles Muñoz-Martín Mabrouka Oustani Baelhadj Hamdi-Aïssa Elvira Perona Pilar Mateo 《Environmental microbiology》2022,24(1):451-474
The hyperarid Sahara Desert presents extreme and persistent dry conditions with a limited number of hours during which the moisture availability, temperature and light allow phototrophic growth. Some cyanobacteria can live in these hostile conditions by seeking refuge under (hypolithic) or inside (endolithic) rocks, by colonizing porous spaces (cryptoendoliths) or fissures in stones (chasmoendoliths). Chroococcidiopsis spp. have been reported as the dominant or even the only phototrophs in these hot desert lithic communities. However, the results of this study reveal the high diversity of and variability in cyanobacteria among the sampled habitats in the Sahara Desert. The chasmoendolithic samples presented high coccoid cyanobacteria abundances, although the dominant cyanobacteria were distinct among different locations. A high predominance of a newly described cyanobacterium, Pseudoacaryochloris sahariense, was found in hard, compact, and more opaque stones with cryptoendolithic colonization. On the other hand, the hypolithic samples were dominated by filamentous, non-heterocystous cyanobacteria. Thermophysiological bioassays confirmed desiccation and extreme temperature tolerance as drivers in the cyanobacterial community composition of these lithic niches. The results of the present study provide key factors for understanding life strategies under polyextreme environmental conditions. The isolated strains, especially the newly described cyanobacterium P. sahariense, might represent suitable microorganisms in astrobiology studies aimed at investigating the limits of life. 相似文献
5.
Cyanobacteria drive community composition and functionality in rock–soil interface communities
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Angel Valverde Thulani P. Makhalanyane Mary Seely Don A. Cowan 《Molecular ecology》2015,24(4):812-821
Most ecological research on hypoliths, significant primary producers in hyperarid deserts, has focused on the diversity of individual groups of microbes (i.e. bacteria). However, microbial communities are inherently complex, and the interactions between cyanobacteria, heterotrophic bacteria, protista and metazoa are likely to be very important for ecosystem functioning. Cyanobacterial and heterotrophic bacterial communities were analysed by pyrosequencing, while metazoan and protistan communities were assessed by T‐RFLP analysis. Microbial functionality was estimated using carbon substrate utilization. Cyanobacterial community composition was significant in shaping community structure and function in hypoliths. Ecological network analysis showed that most significant co‐occurrences were positive, representing potential synergistic interactions. There were several highly interconnected associations (modules), and specific cyanobacteria were important in driving the modular structure of hypolithic networks. Together, our results suggest that hypolithic cyanobacteria have strong effects on higher trophic levels and ecosystem functioning. 相似文献
6.
Azúa-Bustos A González-Silva C Mancilla RA Salas L Gómez-Silva B McKay CP Vicuña R 《Microbial ecology》2011,61(3):568-581
The Atacama Desert is one of the driest places on Earth, with an arid core highly adverse to the development of hypolithic
cyanobacteria. Previous work has shown that when rain levels fall below ~1 mm per year, colonization of suitable quartz stones
falls to virtually zero. Here, we report that along the coast in these arid regions, complex associations of cyanobacteria,
archaea, and heterotrophic bacteria inhabit the undersides of translucent quartz stones. Colonization rates in these areas,
which receive virtually no rain but mainly fog, are significantly higher than those reported inland in the hyperarid zone
at the same latitude. Here, hypolithic colonization rates can be up to 80%, with all quartz rocks over 20 g being colonized.
This finding strongly suggests that hypolithic microbial communities thriving in the seaward face of the Coastal Range can
survive with fog as the main regular source of moisture. A model is advanced where the development of the hypolithic communities
under quartz stones relies on a positive feedback between fog availability and the higher thermal conductivity of the quartz
rocks, which results in lower daytime temperatures at the quartz–soil interface microenvironment. 相似文献
7.
Fiona K. Y. Wong Donnabella C. Lacap Maggie C. Y. Lau J. C. Aitchison Donald A. Cowan Stephen B. Pointing 《Microbial ecology》2010,60(4):730-739
The hypolithic microbial community associated with quartz pavement at a high-altitude tundra location in central Tibet is described. A small-scale ecological survey indicated that 36% of quartz rocks were colonized. Community profiling using terminal restriction fragment length polymorphism revealed no significant difference in community structure among a number of colonized rocks. Real-time quantitative PCR and phylogenetic analysis of environmental phylotypes obtained from clone libraries were used to elucidate community structure across all domains. The hypolithon was dominated by cyanobacterial phylotypes (73%) with relatively low frequencies of other bacterial phylotypes, largely represented by the chloroflexi, actinobacteria, and bacteriodetes. Unidentified crenarchaeal phylotypes accounted for 4% of recoverable phylotypes, while algae, fungi, and mosses were indicated by a small fraction of recoverable phylotypes. 相似文献
8.
Hypolithic communities represent important reservoirs of microbial life in hyper-arid deserts. A number of studies on the diversity and ecology of these communities from different geographic areas have been reported in the past decade, but the spatial distribution of the different components of these communities is still not understood. Moss- and cyanobacteria-dominated hypolithic community morphotypes from Miers Valley (McMurdo Dry Valleys, East Antarctica) were analyzed by electron microscopy in order to characterize the microscale spatial structure. The two communities showed a high degree of internal organization, but differing according to the biological composition. In moss-dominated hypoliths, the moss plantlets are intermixed with mineral fragments of soil origin. However, in cyanobacteria-dominated hypoliths, a layered spatial organization was structured by filamentous cyanobacteria and associated extracellular polymeric components. While moss cells were lacking in cyanobacteria-dominated communities, biofilms formed by cyanobacteria and heterotrophic bacteria were observed in both community morphotypes. The water-holding capacity of both live and dead moss cells and the associated organic matrix, together with the protective properties of the extracellular polymeric substances, could facilitate the survival and activity of these communities. Similar structural strategies can favor the survival of microbial communities in different extreme environments. 相似文献
9.
Subramanya Rao Yuki Chan Donnabella C. Bugler-Lacap Ashish Bhatnagar Monica Bhatnagar Stephen B. Pointing 《Indian journal of microbiology》2016,56(1):35-45
A culture-independent diversity assessment of archaea, bacteria and fungi in the Thar Desert in India was made. Six locations in Ajmer, Jaisalmer, Jaipur and Jodhupur included semi-arid soils, arid soils, arid sand dunes, plus arid cryptoendolithic substrates. A real-time quantitative PCR approach revealed that bacteria dominated soils and cryptoendoliths, whilst fungi dominated sand dunes. The archaea formed a minor component of all communities. Comparison of rRNA-defined community structure revealed that substrate and climate rather than location were the most parsimonious predictors. Sequence-based identification of 1240 phylotypes revealed that most taxa were common desert microorganisms. Semi-arid soils were dominated by actinobacteria and alpha proteobacteria, arid soils by chloroflexi and alpha proteobacteria, sand dunes by ascomycete fungi and cryptoendoliths by cyanobacteria. Climatic variables that best explained this distribution were mean annual rainfall and maximum annual temperature. Substrate variables that contributed most to observed diversity patterns were conductivity, soluble salts, Ca2+ and pH. This represents an important addition to the inventory of desert microbiota, novel insight into the abiotic drivers of community assembly, and the first report of biodiversity in a monsoon desert system. 相似文献
10.
Hypolithic Cyanobacteria, Dry Limit of Photosynthesis, and Microbial Ecology in the Hyperarid Atacama Desert 总被引:1,自引:0,他引:1
Warren-Rhodes KA Rhodes KL Pointing SB Ewing SA Lacap DC Gómez-Silva B Amundson R Friedmann EI McKay CP 《Microbial ecology》2006,52(3):389-398
The occurrence of hypolithic cyanobacteria colonizing translucent stones was quantified along the aridity gradient in the Atacama Desert in Chile, from less arid areas to the hyperarid core where photosynthetic life and thus primary production reach their limits. As mean rainfall declines from 21 to ≤2 mm year−1, the abundance of hypolithic cyanobacteria drops from 28 to <0.1%, molecular diversity declines threefold, and organic carbon residence times increase by three orders of magnitude. Communities contained a single Chroococcidiopsis morphospecies with heterotrophic associates, yet molecular analysis revealed that each stone supported a number of unique 16S rRNA gene-defined genotypes. A fivefold increase in steady-state residence times for organic carbon within communities in the hyperarid core (3200 years turnover time) indicates a significant decline in biological carbon cycling. Six years of microclimate data suggest that the dry limit corresponds to ≤5 mm year−1 rainfall and/or decadal periods of no rain, with <75 h year−1 of liquid water available to cyanobacteria under light conditions suitable for photosynthesis. In the hyperarid core, hypolithic cyanobacteria are rare and exist in small spatially isolated islands amidst a microbially depauperate bare soil. These findings suggest that photosynthetic life is extremely unlikely on the present-day surface of Mars, but may have existed in the past. If so, such microhabitats would probably be widely dispersed, difficult to detect, and millimeters away from virtually lifeless surroundings. 相似文献
11.
Molecular characterization of endolithic cyanobacteria inhabiting exposed dolomite in central Switzerland 总被引:2,自引:0,他引:2
The phototrophic microbial community inhabiting exposed dolomite in the alpine Piora Valley (Switzerland) forms a distinct endolithic bilayer that features adjacent red dolomite (exterior) and green dolomite (interior) layers that are c. 0.5-1 mm below the rock surface. Characterization of the community, with an emphasis on cyanobacteria, was conducted with culture-dependent and -independent approaches. Direct microscopy of green dolomite revealed four distinct morphotypes consistent with Chlorophyta genera Chlorella and Stichococcus and the Cyanobacterial genera Nostoc and Calothrix, whereas only Stichococcus and Nostoc were observed in the red dolomite. Enrichment in BG-11 media resulted in the growth of Chlorella and Stichococcus. Denaturing gradient gel electrophoresis (DGGE) analysis of DNA extracted from the enrichment revealed two dominant phylotypes with sequence similarity to Chlorella osrokiniana chloroplast and the cyanobacteria genus Leptolyngbya. 16S rRNA gene-based DGGE analysis of DNA extracted directly from both layers indicated that although both layers harboured phylotypes most similar to the Cyanobacterial genera Nostoc, Chroococcidiopsis, and Microcoleus, and the Chlorophyte Stichococcus bacillaris, the two layers also harboured unique genera such as Scytonema, and Symploca (red, external layer of dolomite) and Chlorella (green, internal layer of dolomite). The unique community structure of each layer suggests a selection process directed by the pressures of the endolithic environment. We conclude that the overall composition of the phototrophic community closely resembles that of endolithic communities located in extreme habitats, suggesting that a cosmopolitan community inhabits this defined niche. 相似文献
12.
Michal Gwizdala Pedro H. Lebre Gillian Maggs-Kölling Eugene Marais Don A. Cowan Tjaart P. J. Krüger 《Environmental microbiology》2021,23(7):3867-3880
In hyper-arid soil environments, photosynthetic microorganisms are largely restricted to hypolithic (sub-lithic) habitats: i.e., on the ventral surfaces of translucent pebbles in desert pavements. Here, we combined fluorometric, spectroscopic, biochemical and metagenomic approaches to investigate in situ the light transmission properties of quartz stones in the Namib Desert, and assess the photosynthetic activity of the underlying hypolithic cyanobacterial biofilms. Quartz pebbles greatly reduced the total photon flux to the ventral surface biofilms and filtered out primarily the short wavelength portion of the solar spectrum. Chlorophylls d and f were not detected in biofilm pigment extracts; however, hypolithic cyanobacterial communities showed some evidence of adaptation to sub-lithic conditions, including the prevalence of genes encoding Helical Carotenoid Proteins, which are associated with desiccation stress. Under water-saturated conditions, hypolithic communities showed no evidence of light stress, even when the quartz stones were exposed to full midday sunlight. This initial study creates a foundation for future in-situ and laboratory exploration of various adaptation mechanisms employed by photosynthetic organisms forming hypolithic microbial communities. 相似文献
13.
The diversity and nitrogenase activity of epilithic marine microbes in a Holocene beach rock (Heron Island, Great Barrier Reef, Australia) with a proposed biological calcification "microbialite" origin were examined. Partial 16S rRNA gene sequences from the dominant mat (a coherent and layered pink-pigmented community spread over the beach rock) and biofilms (nonstratified, differently pigmented microbial communities of small shallow depressions) were retrieved using denaturing gradient gel electrophoresis (DGGE), and a clone library was retrieved from the dominant mat. The 16S rRNA gene sequences and morphological analyses revealed heterogeneity in the cyanobacterial distribution patterns. The nonheterocystous filamentous genus Blennothrix sp., phylogenetically related to Lyngbya, dominated the mat together with unidentified nonheterocystous filaments of members of the Pseudanabaenaceae and the unicellular genus Chroococcidiopsis. The dominance and three-dimensional intertwined distribution of these organisms were confirmed by nonintrusive scanning microscopy. In contrast, the less pronounced biofilms were dominated by the heterocystous cyanobacterial genus Calothrix, two unicellular Entophysalis morphotypes, Lyngbya spp., and members of the Pseudanabaenaceae family. Cytophaga-Flavobacterium-Bacteroides and Alphaproteobacteria phylotypes were also retrieved from the beach rock. The microbial diversity of the dominant mat was accompanied by high nocturnal nitrogenase activities (as determined by in situ acetylene reduction assays). A new DGGE nifH gene optimization approach for cyanobacterial nitrogen fixers showed that the sequences retrieved from the dominant mat were related to nonheterocystous uncultured cyanobacterial phylotypes, only distantly related to sequences of nitrogen-fixing cultured cyanobacteria. These data stress the occurrence and importance of nonheterocystous epilithic cyanobacteria, and it is hypothesized that such epilithic cyanobacteria are the principal nitrogen fixers of the Heron Island beach rock. 相似文献
14.
Michail M. Yakimov Laura Giuliano Simone Cappello Renata Denaro Peter N. Golyshin 《Origins of life and evolution of the biosphere》2007,37(2):177-188
The composition of a metabolically active prokaryotic community thriving in hydrothermal mud fluids of the deep-sea hypersaline
anoxic Western Urania Basin was characterized using rRNA-based phylogenetic analysis of a clone library. The physiologically
active prokaryotic assemblage in this extreme environment showed a great genetic diversity. Most members of the microbial
community appeared to be affiliated to yet uncultured organisms from similar ecosystems, i.e., deep-sea hypersaline basins
and hydrothermal vents. The bacterial clone library was dominated by phylotypes affiliated with the epsilon-Proteobacteria subdivision recognized as an ecologically significant group of bacteria inhabiting deep-sea hydrothermal environments. Almost
18% of all bacterial clones were related to delta-Proteobacteria, suggesting that sulfate reduction is one of the dominant metabolic processes occurring in warm mud fluids. The remaining
bacterial phylotypes were related to alpha- and beta-Proteobacteria, Actinobacteria, Bacteroides, Deinococcus-Thermus, KB1 and OP-11 candidate divisions. Moreover, a novel monophyletic clade, deeply branched with unaffiliated 16S rDNA clones
was also retrieved from deep-sea sediments and halocline of Urania Basin. Archaeal diversity was much lower and detected phylotypes
included organisms affiliated exclusively with the Euryarchaeota. More than 96% of the archaeal clones belonged to the MSBL-1 candidate order recently found in hypersaline anoxic environments,
such as endoevaporitic microbial mats, Mediterranean deep-sea mud volcanoes and anoxic basins. Two phylotypes, represented
by single clones were related to uncultured groups DHVE-1 and ANME-1. Thus, the hydrothermal mud of hypersaline Urania Basin
seems to contain new microbial diversity. The prokaryotic community was significantly different from that occurring in the
upper layers of the Urania Basin since 60% of all bacterial and 40% of all archaeal phylotypes were obtained only from mud
fluids. The uniqueness of the composition of the active prokaryotic community could be explained by the complex environmental
conditions at the site. The interaction of oxygenated warm mud fluids with the cold hypersaline brine of the Urania Basin
seems to simultaneously select for various metabolic processes, such as aerobic and anaerobic heterotrophy, sulfide- and methane-dependent
chemotrophy along with anaerobic oxidation of methane, sulfate- and metal-reduction. 相似文献
15.
The freshwater microbial community in a recreational area of Xochimilco, México was investigated and compared based on spatial
(three different sites) and temporal (dry and rainy seasons) environmental variables. Many of the 16S- and 18S rRNA gene sequences
recovered by DGGE fingerprinting analysis were related to phototrophic microbial phylotypes of known identity. Our genetic
and morphological analysis indicated the ubiquitous presence of the microeukaryotic green algae Desmodesmus-Scenedesmus spp. and of the unicellular cyanobacteria Cyanobium spp. as the most representative populations in the samples. While 18S rRNA-DGGE fingerprinting analysis revealed a homogeneous
community composition across sites and seasons, the 16S rRNA showed significant differences between localities and seasons.
None of the cyanobacteria species with potential to produce toxins were identified across the investigated samples. Correlations
between biotic and abiotic variables evidenced an important difference between the dry and the rainy season, with a greater
consistency in data from the rainy season. According to Principal Component Analysis (PCA), a strong relation between inorganic
nitrogen, species richness, and subaquatic irradiance determines environmental variability in Xochimilco. Complementary and
relevant data in results obtained from microscopy, fingerprinting, and statistical analysis applied in ecology indicate that
a multifaceted approach to the study of microbial communities is necessary to accomplish a comprehensive scientific framework
and to generate proper management strategies. 相似文献
16.
Thomas DN 《Trends in microbiology》2005,13(3):87-88
Polar deserts are not devoid of life despite the extreme low temperature and scarcity of water. Recently, patterned stone fields--caused by periglacial activity--have been surveyed in the Arctic and Antarctic. It was found that the productivity of the cyanobacteria and algae (hypoliths) that colonise the underside of the stones is strongly related to the pattern of the stones. The hypolith assemblages were in some cases as productive as lichens, bryophytes and plants that resided nearby. 相似文献
17.
18.
López-García P Kazmierczak J Benzerara K Kempe S Guyot F Moreira D 《Extremophiles : life under extreme conditions》2005,9(4):263-274
Lake Van harbors the largest known microbialites on Earth. The surface of these huge carbonate pinnacles is covered by coccoid cyanobacteria whereas their central axis is occupied by a channel through which neutral, relatively Ca-enriched, groundwater flows into highly alkaline (pH ~9.7) Ca-poor lake water. Previous microscopy observations showed the presence of aragonite globules composed by rounded nanostructures of uncertain origin that resemble similar bodies found in some meteorites. Here, we have carried out fine-scale mineralogical and microbial diversity analyses from surface and internal microbialite samples. Electron transmission microscopy revealed that the nanostructures correspond to rounded aragonite nanoprecipitates. A progressive mineralization of cells by the deposition of nanoprecipitates on their surface was observed from external towards internal microbialite areas. Molecular diversity studies based on 16S rDNA amplification revealed the presence of bacterial lineages affiliated to the Alpha-, Beta- and Gammaproteobacteria, the Cyanobacteria, the Cytophaga-Flexibacter-Bacteroides (CFB) group, the Actinobacteria and the Firmicutes. Cyanobacteria and CFB members were only detected in surface layers. The most abundant and diverse lineages were the Firmicutes (low GC Gram positives). To the exclusion of cyanobacteria, the closest cultivated members to the Lake Van phylotypes were most frequently alkaliphilic and/or heterotrophic bacteria able to degrade complex organics. These heterotrophic bacteria may play a crucial role in the formation of Lake Van microbialites by locally promoting carbonate precipitation. 相似文献
19.
《Bioscience, biotechnology, and biochemistry》2013,77(4):906-915
We constructed a bacterial 16S rRNA gene clone library from the gut microbial community of O. formosanus and phylogenetically analyzed it in order to contribute to the evolutional study of digestive symbiosis and method development for termite control. After screening by restriction fragment length polymorphism (RFLP) analysis, 56 out of 280 clones with unique RFLP patterns were sequenced and phylogenetically analyzed. The representative phylotypes were affiliated to four phylogenetic groups, Firmicutes, the Bacteroidetes/Chlorobi group, Proteobacteria, and Actinobacteria of the domain Bacteira. No one clone affiliated with the phylum Spirochaetes was identified, in contrast to the case of wood-feeding termites. The phylogenetic analysis revealed that nearly half of the representative clones (25 phylotypes) formed monophyletic clusters with clones obtained from other termite species, especially with the sequences retrieved from fungus-growing termites. These results indicate that the presence of termite-specific bacterial lineages implies a coevolutional relationship of gut microbes and host termites. 相似文献
20.
Laura Villanueva Nicole Bale Ellen C. Hopmans Stefan Schouten Jaap S. Sinninghe Damsté 《Environmental microbiology》2014,16(3):774-787
Sulphoquinovosyldiacylglycerols (SQDG) are polar sulphur‐containing membrane lipids, whose presence has been related to a microbial strategy to adapt to phosphate deprivation. In this study, we have targeted the sqdB gene coding the uridine 5′‐diphosphate‐sulphoquinovose (UDP‐SQ) synthase involved in the SQDG biosynthetic pathway to assess potential microbial sources of SQDGs in the marine environment. The phylogeny of the sqdB‐coding protein reveals two distinct clusters: one including green algae, higher plants and cyanobacteria, and another one comprising mainly non‐photosynthetic bacteria, as well as other cyanobacteria and algal groups. Evolutionary analysis suggests that the appearance of UDP‐SQ synthase occurred twice in cyanobacterial evolution, and one of those branches led to the diversification of the protein in members of the phylum Proteobacteria. A search of homologues of sqdB‐proteins in marine metagenomes strongly suggested the presence of heterotrophic bacteria potential SQDG producers. Application of newly developed sqdB gene primers in the marine environment revealed a high diversity of sequences affiliated to cyanobacteria and Proteobacteria in microbial mats, while in North Sea surface water, most of the detected sqdB genes were attributed to the cyanobacterium Synechococcus sp. Lipid analysis revealed that specific SQDGs were characteristic of microbial mat depth, suggesting that SQDG lipids are associated with specific producers. 相似文献