Bacterial diversity at different depths in lead-zinc mine tailings as revealed by 16S rRNA gene libraries

Bacterial communities at 10 cm, 100 cm, and 200 cm depths in a 100-year-old lead-zinc tailing heap were evaluated by constructing 16S rRNA gene libraries. In total, 98 operational taxonomic units (OTUs) were identified from 193 clones at a 3% sequence difference level. The OTU number and species richness decreased with the depth. Species composition was significantly different between the three libraries. Fifty-seven percent of the examined clones were Acidobacteria and 27% belonged to Proteobacteria. Other sequences included Chloroflexi, Firmicutes, Chlamydiae, Actinobacteria, Gemmatimonadetes, Nitrospira, and three unclassified OTUs. Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Firmicutes, and Actinobacteria were mainly distributed in the rhizosphere of naturally colonizing plants; however, Deltaproteobacteria, Acidobacteria, and Chloroflexi tended to inhabit the deeper tailings (below the 100 cm-depth).     

胜利油藏不同时间细菌群落结构的比较

利用聚合酶链式反应-变性梯度凝胶电泳(PCR-DGGE)和构建16S rRNA基因克隆文库2种方法,对孤岛油田两口井(注水井G和采油井L)在相距9个月的2个时间点(A和B)所采集样品的细菌群落结构进行了比较。DGGE图谱聚类分析表明注水井在2个时间点的微生物群落结构相似性为48.1%,而采油井的相似性只有28.7%。16S rRNA基因克隆文库结果表明,A时间点样品G中的优势菌群为Betaproteobacteria、Gammaproteobacteria,还有Deferribacteres、Firmicutes、Bacteroidetes等;而样品L中,Gammaproteobacteria中的Moraxellaceae含量达到97%。B时间点G中除了优势菌Betaproteobacteria之外,Deferribacteres的数量显著增加,成为优势菌;而L在B时间点优势菌除Gammaproteobacteria外,还有Betaproteobacteria和Firmicutes。采油井中的微生物群落结构随时间发生了显著改变,而注水井变化不显著。这一结果部分揭示了微生物采油过程中地层微生物群落的变化规律,有助于进一步阐明微生物驱油的机理。     

Comparison of microbial community compositions of injection and production well samples in a long-term water-flooded petroleum reservoir

Water flooding plays an important role in recovering oil from depleted petroleum reservoirs. Exactly how the microbial communities of production wells are affected by microorganisms introduced with injected water has previously not been adequately studied. Using denaturing gradient gel electrophoresis (DGGE) approach and 16S rRNA gene clone library analysis, the comparison of microbial communities is carried out between one injection water and two production waters collected from a working block of the water-flooded Gudao petroleum reservoir located in the Yellow River Delta. DGGE fingerprints showed that the similarities of the bacterial communities between the injection water and production waters were lower than between the two production waters. It was also observed that the archaeal composition among these three samples showed no significant difference. Analysis of the 16S rRNA gene clone libraries showed that the dominant groups within the injection water were Betaproteobacteria, Gammaproteobacteria and Methanomicrobia, while the dominant groups in the production waters were Gammaproteobacteria and Methanobacteria. Only 2 out of 54 bacterial operational taxonomic units (OTUs) and 5 out of 17 archaeal OTUs in the injection water were detected in the production waters, indicating that most of the microorganisms introduced by the injection water may not survive to be detected in the production waters. Additionally, there were 55.6% and 82.6% unique OTUs in the two production waters respectively, suggesting that each production well has its specific microbial composition, despite both wells being flooded with the same injection water.     

Soil characteristics more strongly influence soil bacterial communities than land-use type

To gain insight into the factors driving the structure of bacterial communities in soil, we applied real-time PCR, PCR-denaturing gradient gel electrophoreses, and phylogenetic microarray approaches targeting the 16S rRNA gene across a range of different land usages in the Netherlands. We observed that the main differences in the bacterial communities were not related to land-use type, but rather to soil factors. An exception was the bacterial community of pine forest soils (PFS), which was clearly different from all other sites. PFS had lowest bacterial abundance, lowest numbers of operational taxonomic units (OTUs), lowest soil pH, and highest C : N ratios. C : N ratio strongly influenced bacterial community structure and was the main factor separating PFS from other fields. For the sites other than PFS, phosphate was the most important factor explaining the differences in bacterial communities across fields. Firmicutes were the most dominant group in almost all fields, except in PFS and deciduous forest soils (DFS). In PFS, Alphaproteobacteria was most represented, while in DFS, Firmicutes and Gammaproteobacteria were both highly represented. Interestingly, Bacillii and Clostridium OTUs correlated with pH and phosphate, which might explain their high abundance across many of the Dutch soils. Numerous bacterial groups were highly correlated with specific soil factors, suggesting that they might be useful as indicators of soil status.     

Influence of Hand Rearing and Bird Age on the Fecal Microbiota of the Critically Endangered Kakapo

The critically endangered New Zealand parrot, the kakapo, is subject to an intensive management regime aiming to maintain bird health and boost population size. Newly hatched kakapo chicks are subjected to human intervention and are frequently placed in captivity throughout their formative months. Hand rearing greatly reduces mortality among juveniles, but the potential long-term impact on the kakapo gut microbiota is uncertain. To track development of the kakapo gut microbiota, fecal samples from healthy, prefledged juvenile kakapos, as well as from unrelated adults, were analyzed by using 16S rRNA gene amplicon pyrosequencing. Following the original sampling, juvenile kakapos underwent a period of captivity, so further sampling during and after captivity aimed to elucidate the impact of captivity on the juvenile gut microbiota. Variation in the fecal microbiota over a year was also investigated, with resampling of the original juvenile population. Amplicon pyrosequencing revealed a juvenile fecal microbiota enriched with particular lactic acid bacteria compared to the microbiota of adults, although the overall community structure did not differ significantly among kakapos of different ages. The abundance of key operational taxonomic units (OTUs) was correlated with antibiotic treatment and captivity, although the importance of these factors could not be proven unequivocally within the bounds of this study. Finally, the microbial community structure of juvenile and adult kakapos changed over time, reinforcing the need for continual monitoring of the microbiota as part of regular health screening.     

T-RFLP analysis of bacterial communities in the midguts of Apis mellifera and Apis cerana honey bees in Thailand

This study investigated bacterial community structures in the midguts of Apis mellifera and Apis cerana in Thailand to understand how bacterial communities develop in Apis species. The bacterial species present in replicate colonies from different locations and life stages were analysed. PCR amplification of bacterial 16S rRNA gene fragments and terminal restriction fragment length polymorphism analyses revealed a total of 16 distinct terminal restriction fragments (T-RFs), 12 of which were shared between A. mellifera and A. cerana populations. The T-RFs were affiliated to Beta- and Gammaproteobacteria, Firmicutes and Actinomycetes. The Gammaproteobacteria were found to be common in all stages of honey bee, but in addition, the Firmicutes group was found to be present in the worker bees. Bacterial community structure showed no difference amongst the replicate colonies, but was affected to some degree by geographical location, life stage and species of honey bees.     

Microbial communities in long-term, water-flooded petroleum reservoirs with different in situ temperatures in the Huabei Oilfield, China

The distribution of microbial communities in the Menggulin (MGL) and Ba19 blocks in the Huabei Oilfield, China, were studied based on 16S rRNA gene analysis. The dominant microbes showed obvious block-specific characteristics, and the two blocks had substantially different bacterial and archaeal communities. In the moderate-temperature MGL block, the bacteria were mainly Epsilonproteobacteria and Alphaproteobacteria, and the archaea were methanogens belonging to Methanolinea, Methanothermobacter, Methanosaeta, and Methanocella. However, in the high-temperature Ba19 block, the predominant bacteria were Gammaproteobacteria, and the predominant archaea were Methanothermobacter and Methanosaeta. In spite of shared taxa in the blocks, differences among wells in the same block were obvious, especially for bacterial communities in the MGL block. Compared to the bacterial communities, the archaeal communities were much more conserved within blocks and were not affected by the variation in the bacterial communities.     

Bacterial community structure associated with the Antarctic soft coral, Alcyonium antarcticum

The structure and composition of microbial communities inhabiting the soft coral Alcyonium antarcticum were investigated across three differentially contaminated sites within McMurdo Sound, Antarctica. Diverse microbial communities were revealed at all sites using culture-based analysis, denaturing gradient gel electrophoresis (DGGE), 16S rRNA gene clone-library analysis, and FISH. Phylogenetic analysis of isolates and retrieved sequences demonstrated close affiliation with known psychrophiles from the Antarctic environment and high similarity to Gammaproteobacteria clades of sponge-associated microorganisms. The majority of bacteria detected with all techniques reside within the Gammaproteobacteria, although other phylogenetic groups including Alpha- and Betaproteobacteria, Bacteroidetes, Firmicutes, Actinomycetales, Planctomycetes, and Chlorobi and bacteria from the functional group of sulfate-reducing bacteria were also present. Multivariate (nMDS) analysis of DGGE banding patterns and principal component analysis of quantitative FISH data revealed no distinct differences in community composition between differentially contaminated sites. Rather, conserved coral-associated bacterial groups were observed within and between sites, providing evidence to support specific coral-microbial interactions. This is the first investigation of microbial communities associated with Antarctic soft corals, and the results suggest that spatially stable microbial associations exist across an environmental impact gradient.     

Bacterial diversity in the rumen of Indian Surti buffalo (Bubalus bubalis), assessed by 16S rDNA analysis

Bacterial communities in buffalo rumen were characterized using a culture-independent approach for a pooled sample of rumen fluid from 3 adult Surti buffaloes. Buffalo rumen is likely to include species of various bacterial phyla, so 16S rDNA sequences were amplified and cloned from the sample. A total of 191 clones were sequenced and similarities to known 16S rDNA sequences were examined. About 62.82% sequences (120 clones) had >90% similarity to the 16S rDNA database sequences. Furthermore, about 34.03% of the sequences (65 clones) were 85–89% similar to 16S rDNA database sequences. For the remaining 3.14%, the similarity was lower than 85%. Phylogenetic analyses were also used to infer the makeup of bacterial communities in the rumen of Surti buffalo. As a result, we distinguished 42 operational taxonomic units (OTUs) based on unique 16S r DNA sequences: 19 OTUs affiliated to an unidentified group (45.23% of total OTUs), 11 OTUs of the phylum Firmicutes, also known as the low G+C group (26.19%), 7 OTUs of theCytophaga-Flexibacter-Bacteroides phylum (16.66%), 4 OTUs of Spirochaetes (9.52%), and 1 OTU of Actinobacteria (2.38%). These include 10 single-clone OTUs, so Good’s coverage (94.76%) of 16S rRNA libraries indicated that sequences identified in the libraries represent the majority of bacterial diversity present in rumen.     

Molecular community analysis of magnesium-rich bittern brine recovered from a Tunisian solar saltern

The microbial community of a magnesium-rich bittern brine saturated with NaCl (380-400 g/L) from a Tunisian solar saltern was investigated using a molecular approach based on 16S rRNA gene analysis and viability tests. The results revealed the existence of microbial flora. Viability test assessment showed that 46.4% of this flora was viable but not detectable by culturability tests. 16S rRNA genes from 49 bacterial clones and 38 archaeal clones were sequenced and phylogenetically analyzed. Eleven operational taxonomic units (OTUs) determined by the DOTUR program with 97% sequence similarity were generated for Bacteria. These OTUs were affiliated with Bacteroidetes and Gammaproteobacteria. The archaeal community composition exhibited more diversity with 38 clones, resulting in 13 OTUs affiliated with the Euryarchaeota phylum. Diversity measurement showed a more diverse archaeal than bacterial community at the saturated pond.     

基于高通量测序的褐飞虱肠道微生物多样性分析

【目的】探明褐飞虱Nilaparvata lugens成虫肠道微生物群落结构和多样性。【方法】分离褐飞虱成虫完整肠道并提取总DNA,利用Illumina MiSeq(PE300)技术对其肠道细菌16S rRNA的V3-V4变异区和真菌ITS2序列进行测序,统计肠道微生物的操作分类单元(operational taxonomic unit, OTU)数量,分析其物种组成、丰度及Alpha多样性。并通过qPCR技术验证随机挑选注释到的4种肠道菌的高通量测序数据的有效性。【结果】分别获得褐飞虱成虫肠道细菌16S rRNA和真菌ITS2优质序列32 395和24 986条,根据序列相似性进行聚类分析分别获得235和128个OTUs。其中,细菌共注释到7个门, 15个纲, 26个目, 45个科和73个属;真菌共鉴定到3个门, 9个纲, 12个目, 15个科和18个属。在门分类水平上,细菌以变形菌门(Proteobacteria)、拟杆菌门(Bacteroidetes)和厚壁菌门(Firmicutes)为优势门类;真菌以子囊菌门(Ascomycota)为绝对优势菌门。在属分类水平上,细菌的优势属为不动杆菌属Acinetobacter以及紫单胞菌科(Porphyromonadaceae)未确定属和毛螺菌科(Lachnospiraceae)未确定属,其丰度分别为36.37%, 17.22%和15.01%;真菌的优势属为粪壳菌纲(Sordariomycetes)未确定属,丰度为95.77%。Alpha多样性分析结果显示,褐飞虱肠道细菌(真菌)的观测物种数、Chao1指数、Shannon指数和Simpson 指数分别为235(128), 262.64(165.40), 3.90(0.91)和0.62(0.75)。4种肠道菌的qPCR结果显示高通量测序数据具有较高的有效性。【结论】褐飞虱成虫肠道细菌和真菌群落整体多样性比较丰富。研究结果为从共生微生物角度解析褐飞虱的环境适应性以及开发基于微生物防治的新技术等方面提供了依据。     

Bacterial Diversity in Linglong Gold Mine,China

Bacteria have been actively regulating cycles of various elements in the environment. To explore the potential bacterial role in gold biogeochemical cycling, this study analyzed the bacterial diversity of mine rock (MR) and surface soil (SS) samples from Linglong gold mine using 16S rRNA gene clone library analysis and cultivation method. From MR, 24 operational taxonomic units (OTUs) were identified from MR, covering 3 phyla and 18 genera. Meanwhile, 24 OTUs were identified from SS, including 4 phyla and 18 genera. Compared with 16S rRNA gene clone library analysis, 28 aerobic and 34 anaerobic isolates were obtained, whereas 26 aerobic and 71 anaerobic strains were isolated from SS. The cultivable bacteria were affiliated with Firmicutes, Proteobacteria and Actinobacteria phyla, and dominated by Firmicutes. These results underscore the high level of bacterial diversity in the gold mine. Our study provides information on the microbial diversity in Linglong gold mine and sheds light on the existence and potential function of bacteria in the gold biogeochemical cycling.     

High through put 16S rRNA gene-based pyrosequencing analysis of the fecal microbiota of high FCR and low FCR broiler growers

The performance of birds appears to vary among the flock of growing broilers which may in part be due to variation in their gut microbiota. In the view of poultry industry, it is desirable to minimise such variation. We investigated metagenomic profile of fecal bacteria in birds with high and low feed conversion ratio (FCR) to identify microbial community linked to low and high FCR by employing high throughput pyrosequencing of 16S rRNA genomic targets. Therefore feeding trial was investigated in order to identify fecal bacteria consistently linked with better feed conversion ratio in bird performance as measured by body weight gain. High-throughput 16S rRNA gene based pyrosequencing was used to provide a comparative analysis of fecal microbial diversity. The fecal microbial community of birds was predominated by Proteobacteria (48.04?% in high FCR and 49.98?% in low FCR), Firmicutes (26.17?% in high FCR and 36.23?% in low FCR), Bacteroidetes (18.62?% in high FCR and 11.66?% in low FCR), as well as unclassified bacteria (15.77?% in high FCR and 14.29?% in low FCR), suggesting that a large portion of fecal microbiota is novel and could be involved in currently unknown functions. The most prevalent bacterial classes in high FCR and low FCR were Gammaproteobacteria, Clostridia and Bacteroidia. However in low FCR birds Phascolarctobacterium, Faecalibacterium and Clostridium predominated among the Clostridia. In FCR comparison of fecal bacteria, about 36 genera were differentially abundant between high and low FCR birds. This information could be used to formulate effective strategies to improve feed efficiency and feed formulation for optimal gut health.     

Water mass-specificity of bacterial communities in the North Atlantic revealed by massively parallel sequencing

Bacterial assemblages from subsurface (100 m depth), meso- (200-1000 m depth) and bathy-pelagic (below 1000 m depth) zones at 10 stations along a North Atlantic Ocean transect from 60°N to 5°S were characterized using massively parallel pyrotag sequencing of the V6 region of the 16S rRNA gene (V6 pyrotags). In a dataset of more than 830,000 pyrotags, we identified 10,780 OTUs of which 52% were singletons. The singletons accounted for less than 2% of the OTU abundance, whereas the 100 and 1000 most abundant OTUs represented 80% and 96% respectively of all recovered OTUs. Non-metric Multi-Dimensional Scaling and Canonical Correspondence Analysis of all the OTUs excluding the singletons revealed a clear clustering of the bacterial communities according to the water masses. More than 80% of the 1000 most abundant OTUs corresponded to Proteobacteria of which 55% were Alphaproteobacteria, mostly composed of the SAR11 cluster. Gammaproteobacteria increased with depth and included a relatively large number of OTUs belonging to Alteromonadales and Oceanospirillales. The bathypelagic zone showed higher taxonomic evenness than the overlying waters, albeit bacterial diversity was remarkably variable. Both abundant and low-abundance OTUs were responsible for the distinct bacterial communities characterizing the major deep-water masses. Taken together, our results reveal that deep-water masses act as bio-oceanographic islands for bacterioplankton leading to water mass-specific bacterial communities in the deep waters of the Atlantic.     

Zooming-in on floral nectar: a first exploration of nectar-associated bacteria in wild plant communities

Floral nectar of some animal-pollinated plants usually harbours highly adapted yeast communities which can profoundly alter nectar characteristics and, therefore, potentially have significant impacts on plant reproduction through their effects on insect foraging behaviour. Bacteria have also been occasionally observed in floral nectar, but their prevalence, phylogenetic diversity and ecological role within plant-pollinator-yeast systems remains unclear. Here we present the first reported survey of bacteria in floral nectar from a natural plant community. Culturable bacteria occurring in a total of 71 nectar samples collected from 27 South African plant species were isolated and identified by 16S rRNA gene sequencing. Rarefaction-based analyses were used to assess operational taxonomic units (OTUs) richness at the plant community level using nectar drops as sampling units. Our results showed that bacteria are common inhabitants of floral nectar of South African plants (53.5% of samples yielded growth), and their communities are characterized by low species richness (18 OTUs at a 16S rRNA gene sequence dissimilarity cut-off of 3%) and moderate phylogenetic diversity, with most isolates belonging to the Gammaproteobacteria. Furthermore, isolates showed osmotolerance, catalase activity and the ability to grow under microaerobiosis, three traits that might help bacteria to overcome important factors limiting their survival and/or growth in nectar.     

Phylogenetic analysis of partial bacterial 16S rDNA sequences of tropical grass pasture soil under Acacia tortilis subsp. raddiana in Senegal

We used direct recovery of bacterial 16S rRNA gene sequences to investigate the bacterial diversity under Acacia tortilis subsp. raddiana, a legume tree naturally growing in the dry land part of Senegal (West Africa). Microbial DNA was purified directly from soil samples and subjected to PCR with primers specific for bacterial 16S rRNA gene sequences. 16S rDNA clone libraries were constructed from two soil samples taken at two dates, i.e. June 25th 1999 (dry season) and August 28th 1999 (rainy season) at depths of 0.25-0.50 m and at 3 m distance from the stem. The 16S rDNA of 117 clones was partially sequenced. Phylogenetic analysis of these sequences revealed extensive diversity (100 phylotypes). Comparative sequence analysis of these clones identified members of the Gammaproteobacteria (35% of the phylotypes) as the most important group, followed by the Firmicutes division with 24%. Alphaproteobacteria, Betaproteobacteria, Acidobacteria and Actinobacteria were found to be less represented. Our data suggest that bacterial communities under Acacia tortilis subsp. raddiana might differ according to the season. The relative compositions of the populations is different in both samples: the Acidobacteria are present in a much higher percentage in the dry season than in the rainy season sample while the inverse effect is observed for the members of the other groups. Within the Gammaproteobacteria we found a shift between the dry season and the rainy season from pseudomonads to Acinetobacter and Escherichia related organisms.     

Phylogenetic analysis of bacteria associated with Laminaria saccharina

Bacterial communities associated with the brown alga Laminaria saccharina from the Baltic Sea and from the North Sea were investigated using denaturing gradient gel electrophoresis and 16S rRNA gene clone libraries. The rhizoid, cauloid, meristem and phyloid revealed different 16S rRNA gene denaturing gradient gel electrophoresis banding patterns indicating a specific association of bacterial communities with different parts of the alga. Associations with cauloid and meristem were more specific, while less specific associations were obtained from the old phyloid. In addition, seasonal and geographical differences in the associated communities were observed. Results from 16S rRNA gene libraries supported these findings. Bacterial phylotypes associated with the alga were affiliated with the Alphaproteobacteria (nine phylotypes), Gammaproteobacteria (nine phylotypes) and the Bacteroidetes group (four phylotypes). A number of bacteria associated with other algae and other marine macroorganisms were among the closest relatives of phylotypes associated with L. saccharina.     

基于高通量测序分析盐角草根部内生细菌多样性及动态规律

【目的】探讨盐角草根部内生细菌群落多样性特征,揭示内生细菌群落结构在宿主关键发育期动态变化规律。【方法】通过罗氏454高通量测序获得内生细菌16S r RNA片段,然后进行生物信息分析。【结果】共获得20363条16S r RNA基因序列。各样品中可操作分类单元(operational taxonomic units,OTUs)在552–941之间。根部内生细菌群落主要包括4个门,其中Proteobacteri门占主导地位,其余依次是Firmicutes,Actinobacteria,Bacteroidetes。在Proteobacteria门中,Gammaproteobacteria是第一大纲,其后是Betaproteobacteria纲。宿主5个发育时期共同拥有7个细菌属,包括Azomonas,Serratia,Pantoea,Serpens,Pseudomonas,Halomonas,Kushneria。整体上看,Gammaproteobacteria纲在宿主5个发育时期呈现增长趋势。优势菌属在5个发育期存在差异,分别为Delftia,Kushneria,Serratia,Pantoea,Erwinia。所有文库总共含2108个特异OTUs,共同拥有5个相同OTUs。花期OTUs数量最多,结种期内生细菌多样性降低。在宿主的5个发育时期中,土壤p H、月均温和土壤盐含量这3个环境因子组成的集合对其内生细菌群落变化具有显著影响。【结论】盐角草内生细菌群落多样性丰富,宿主发育期决定了内生细菌群落结构。     

Culture-dependent and culture-independent assessment of bacteria in the apple phyllosphere

Aims: Bacterial communities in the apple phyllosphere were examined quantitatively and qualitatively by applying culture‐dependent and culture‐independent methods. Methods and Results: Populations estimated by viewing cells stained with 4′,6‐diamidino‐2‐phenylindole generally were at least 100–1000 times greater than populations estimated by culturing on tryptic soy agar (TSA). Of the 44 operational taxonomic units (OTUs; cut‐off threshold of 97%) detected in total, five bacterial orders containing 23 OTUs were identified by culturing on TSA, whereas nine orders containing 33 OTUs were identified by 16S rRNA gene cloning of DNA extracted from apple leaf surfaces. Twelve of the 44 OTUs were shared between cultured isolates and 16S rRNA gene clones and included the orders Burkholderiales, Pseudomonadales, Rhizobiales and Sphingomonadales. Three OTUs within the genus Sphingomonas accounted for 40% of isolates and 68% of clones. The Actinomycetales were found only among isolates, whereas the Bacteroidales, Enterobacteriales, Myxococales and Sphingobacteriales were represented in the 16S rRNA gene clone libraries but were absent among isolates. Conclusions: Culture‐independent methods revealed greater numbers and greater richness of bacteria on apple leaves than found by culturing. Significance and Impact of the Study: This is the first study to directly compare culture‐dependent and independent approaches for assessing bacterial communities in the phyllosphere. The biases introduced by different methods will have a significant impact on studies related to phyllosphere ecology, biological control of plant diseases, reservoirs of antibiotic resistance genes and food safety.     

Microbial community composition of anoxic marine sediments in the Bay of Cádiz (Spain)

The composition of the microbial community inhabiting the anoxic coastal sediments of the Bay of Cádiz (southern Spain) was investigated using a molecular approach consisting of PCR cloning and denaturing gradient gel electrophoresis (DGGE), based on 16S rRNA sequences. The total cell count was 1-5 × 10? cells/g sediment and, as determined by catalyzed reporter deposition-fluorescent in situ hybridization (CARD-FISH), the proportion of Bacteria to Archaea was about 70:30. The analysis of 16S-rRNA gene sequences revealed a wide spectrum of microorganisms, which could be grouped into 111 operational taxonomic units (OTUs). Many of the OTUs showed high phylogenetic similarity to microorganisms living in marine sediments of diverse geographic origin. The phylogenetic groups that were predominantly detected were Firmicutes, Deltaproteobacteria, and Gammaproteobacteria, accounting for 23, 15, and 14% of the clones, respectively. Diversity in the domain Archaea was significantly lower than in the domain Bacteria. The majority of the archaeal OTUs belonged to the Crenarchaeota phylum. Since most of the sequences could not be identified precisely at the genus/species level, the functional roles of the microorganisms in the ecosystem could not be inferred. However, seven OTUs affiliated with the Delta- and Epsilonproteobacteria were identified down to the genus level, with all of the identified genera known to occur in sulfate-rich marine environments.