西北印度洋卡尔斯伯格脊卧蚕热液羽流影响区古菌群落动态变化特征

【目的】热液羽流在浮力上升和非浮力侧向迁移过程中与背景海水不断进行物质和能量的交换。因海底热液活动和洋流的流速流向均存在动态变化性,热液羽流的高度、物理化学参数和微生物群落也随时空发生演化。然而,由于缺乏热液羽流的长期监测和时序取样,微生物群落(尤其是古菌)的多样性及其时空演化尚不清楚。【方法】2018年7月-2019年6月,在卧蚕1号热液喷口东南300 m处放置了一套带有2个沉积物捕获器(分别距海底300 m和40 m)和一个浊度仪(距海底150 m)的锚系潜标,对热液羽流和热液羽流下方颗粒物沉降区的近底水样进行了为期18个月的观测和时序采样。本研究采用16S rRNA基因高通量测序技术研究了水样中古菌群落的多样性,以了解羽流层和近底沉降层古菌群落结构的特征与时空演化。【结果】热原体纲(Thermoplasmata)、甲烷八叠球菌纲(Methanosarcinia)和甲烷杆菌纲(Methanobacteria)等热液来源古菌,当浊度异常值较高时,它们的丰度也增加。从空间上看,热液羽流区和近底沉降区古菌群落结构在门和纲水平上具有相似性,但在目水平上表现出差异性,而且各主要类群的相对丰度也存在差异,其中热原体纲在羽流层中的丰度普遍高于近底沉降层,而氨氧化古菌和甲烷八叠球菌纲在沉降层的丰度较高。【结论】卧蚕热液区东南300 m热液羽流层和近底沉降层均受到了热液的影响,羽流层受热液影响的程度相对更显著,而近底沉降层除了受到一定程度的热液影响外,还可能受到了再悬浮沉积物的影响。热液贡献大小的动态变化和底层沉积物再悬浮可能是造成热液区近端水体古菌群落时空异质性的主要因素。本研究深化了对热液影响区古生菌群落结构及其月际尺度时空分布特征的认识。     

Microbial diversity and biogeochemistry of the Guaymas Basin deep‐sea hydrothermal plume

Hydrothermal plumes are hot spots of microbial biogeochemistry in the deep ocean, yet little is known about the diversity or ecology of microorganisms inhabiting plumes. Recent biogeochemical evidence shows that Mn(II) oxidation in the Guaymas Basin (GB) hydrothermal plume is microbially mediated and suggests that the plume microbial community is distinct from deep‐sea communities. Here we use a molecular approach to compare microbial diversity in the GB plume and in background deep seawater communities, and cultivation to identify Mn(II)‐oxidizing bacteria from plumes and sediments. Despite dramatic differences in Mn(II) oxidation rates between plumes and background seawater, microbial diversity and membership were remarkably similar. All bacterial clone libraries were dominated by Gammaproteobacteria and archaeal clone libraries were dominated by Crenarchaeota. Two lineages, both phylogenetically related to methanotrophs and/or methylotrophs, were consistently over‐represented in the plume. Eight Mn(II)‐oxidizing bacteria were isolated, but none of these or previously identified Mn(II) oxidizers were abundant in clone libraries. Taken together with Mn(II) oxidation rates measured in laboratory cultures and in the field, these results suggest that Mn(II) oxidation in the GB hydrothermal plume is mediated by genome‐level dynamics (gene content and/or expression) of microorganisms that are indigenous and abundant in the deep sea but have yet to be unidentified as Mn(II) oxidizers.     

Microbial communities in semi-consolidated carbonate sediments of the Southwest Indian Ridge

White semi-consolidated carbonate sediments attached to black ferromanganese oxide films were collected approximately 50 km west of a newly discovered hydrothermal field near the Southwest Indian Ridge (SWIR). The biodiversity of the prokaryotic communities within the field was examined using clone library-based culture-independent analysis of the exterior black oxides and the interior white carbonates. Subsequent 16S rRNA gene analysis suggested that Gamma-proteobacteria, Acidobacteria, and Thaumarchaeota members dominated the bacterial and archaeal clone libraries. To further characterize the metabolic processes within the microbial community, analyses of the amoA (coding the alpha subunit of the ammonia monooxygenase for Archaea) and aprA (coding the alpha subunit of the dissimilatory adenosine-5′-phosphosulfate reductase for the sulfate-reducing and sulfur-oxidizing prokaryotes) functional genes were conducted. The functional gene analysis results suggested that Thaumarchaeota and Alphaproteobacteria members were the potential players that participated in N and S cycles in this marine carbonate sedimentary environment. This paper is the first to describe the microbial communities and their potential metabolic pathways within the semi-consolidated carbonate sediments of the SWIR.     

西北印度洋卡尔斯伯格脊卧蚕热液羽流影响区细菌群落结构特征及其演化

【目的】热液羽流影响区包括热液羽流流经区域和羽流中性浮力层下方受热液颗粒物影响的区域。随着热液羽流的演化,热液羽流影响区内微生物群落的结构组成也会发生相应的变化,但是,由于观测和取样困难等原因,迄今热液羽流影响区不同空间位置微生物的群落结构特征及其在月际尺度上的演化尚不清楚。【方法】中国大洋49航次在卧蚕1号热液喷口东南侧300 m处投放了沉积物捕获器锚系,在不同离底高度开展了为期18个月的观测和时序采水。本文采用Illumina MiSeq高通量测序技术对水样中的微生物类群进行测序分析,结合现场实时探测的浊度异常资料,研究卧蚕热液区附近中性浮力羽流和热液颗粒沉降区细菌群落结构的特征和演化及其影响因素。【结果】结果表明,样品中细菌群落以γ-变形菌纲(Gammaproteobacteria)、弯曲菌纲(Camplylobacteria)、α-变形菌纲(Alphaproteobacteria)、拟杆菌纲(Bacteroidia)、梭菌纲(Clostridia)和脱硫叶菌纲(Desulfobulbia)为主。在时间上,优势类群的相对丰度随浊度起伏发生变化,当浊度异常值升高时,弯曲菌纲相对丰度...     

Tectonic and geological setting influence hot spring microbiology

Hydrothermal systems form at divergent and convergent boundaries of lithospheric plates and within plates due to weakened crust and mantle plumes, playing host to diverse microbial ecosystems. Little is known of how differences in tectonic setting influence the geochemical and microbial compositions of these hydrothermal ecosystems. Here, coordinated geochemical and microbial community analyses were conducted on 87 high-temperature (>65°C) water and sediment samples from hot springs in Yellowstone National Park, Wyoming, USA (n = 41; mantle plume setting), Iceland (n = 41, divergent boundary), and Japan (n = 5; convergent boundary). Region-specific variation in geochemistry and sediment-associated 16S rRNA gene amplicon sequence variant (ASV) composition was observed, with 16S rRNA gene assemblages being nearly completely distinguished by region and pH being the most explanatory parameter within regions. Several low abundance ASVs exhibited cosmopolitan distributions across regions, while most high-abundance ASVs were only identified in specific regions. The presence of some cosmopolitan ASVs across regions argues against dispersal limitation primarily shaping the distribution of taxa among regions. Rather, the results point to local tectonic and geologic characteristics shaping the geochemistry of continental hydrothermal systems that then select for distinct microbial assemblages. These results provide new insights into the co-evolution of hydrothermal systems and their microbial communities.     

Finding a needle in the virus metagenome haystack--micro-metagenome analysis captures a snapshot of the diversity of a bacteriophage armoire

Viruses are ubiquitous in the oceans and critical components of marine microbial communities, regulating nutrient transfer to higher trophic levels or to the dissolved organic pool through lysis of host cells. Hydrothermal vent systems are oases of biological activity in the deep oceans, for which knowledge of biodiversity and its impact on global ocean biogeochemical cycling is still in its infancy. In order to gain biological insight into viral communities present in hydrothermal vent systems, we developed a method based on deep-sequencing of pulsed field gel electrophoretic bands representing key viral fractions present in seawater within and surrounding a hydrothermal plume derived from Loki's Castle vent field at the Arctic Mid-Ocean Ridge. The reduction in virus community complexity afforded by this novel approach enabled the near-complete reconstruction of a lambda-like phage genome from the virus fraction of the plume. Phylogenetic examination of distinct gene regions in this lambdoid phage genome unveiled diversity at loci encoding superinfection exclusion- and integrase-like proteins. This suggests the importance of fine-tuning lyosgenic conversion as a viral survival strategy, and provides insights into the nature of host-virus and virus-virus interactions, within hydrothermal plumes. By reducing the complexity of the viral community through targeted sequencing of prominent dsDNA viral fractions, this method has selectively mimicked virus dominance approaching that hitherto achieved only through culturing, thus enabling bioinformatic analysis to locate a lambdoid viral "needle" within the greater viral community "haystack". Such targeted analyses have great potential for accelerating the extraction of biological knowledge from diverse and poorly understood environmental viral communities.     

Geochemical and microbiological evidence for a hydrogen-based,hyperthermophilic subsurface lithoautotrophic microbial ecosystem (HyperSLiME) beneath an active deep-sea hydrothermal field

Subsurface microbial communities supported by geologically and abiologically derived hydrogen and carbon dioxide from the Earths interior are of great interest, not only with regard to the nature of primitive life on Earth, but as potential analogs for extraterrestrial life. Here, for the first time, we present geochemical and microbiological evidence pointing to the existence of hyperthermophilic subsurface lithoautotrophic microbial ecosystem (HyperSLiME) dominated by hyperthermophilic methanogens beneath an active deep-sea hydrothermal field in the Central Indian Ridge. Geochemical and isotopic analyses of gaseous components in the hydrothermal fluids revealed heterogeneity of both concentration and carbon isotopic compositions of methane between the main hydrothermal vent (0.08 mM and –13.8 PDB, respectively) and the adjacent divergent vent site (0.2 mM and –18.5 PDB, respectively), representing potential subsurface microbial methanogenesis, at least in the divergent vent emitting more ¹³C-depleted methane. Extremely high abundance of magmatic energy sources such as hydrogen (2.5 mM) in the fluids also encourages a hydrogen-based, lithoautotrophic microbial activity. Both cultivation and cultivation-independent molecular analyses suggested the predominance of Methanococcales members in the superheated hydrothermal emissions and chimney interiors along with the other major microbial components of Thermococcales members. These results imply that a HyperSLiME, consisting of methanogens and fermenters, occurs in this tectonically active subsurface zone, strongly supporting the existence of hydrogen-driven subsurface microbial communities.     

Spatial distribution of marine crenarchaeota group I in the vicinity of deep-sea hydrothermal systems

Distribution profiles of marine crenarchaeota group I in the vicinity of deep-sea hydrothermal systems were mapped with culture-independent molecular techniques. Planktonic samples were obtained from the waters surrounding two geographically and geologically distinct hydrothermal systems, and the abundance of marine crenarchaeota group I was examined by 16S ribosomal DNA clone analysis, quantitative PCR, and whole-cell fluorescence in situ hybridization. A much higher proportion of marine crenarchaeota group I within the microbial community was detected in deep-sea hydrothermal environments than in normal deep and surface seawaters. The highest proportion was always obtained from the ambient seawater adjacent to hydrothermal emissions and chimneys but not from the hydrothermal plumes. These profiles were markedly different from the profiles of epsilon-Proteobacteria, which are abundant in the low temperatures of deep-sea hydrothermal environments.     

Spatial Distribution of Marine Crenarchaeota Group I in the Vicinity of Deep-Sea Hydrothermal Systems

Distribution profiles of marine crenarchaeota group I in the vicinity of deep-sea hydrothermal systems were mapped with culture-independent molecular techniques. Planktonic samples were obtained from the waters surrounding two geographically and geologically distinct hydrothermal systems, and the abundance of marine crenarchaeota group I was examined by 16S ribosomal DNA clone analysis, quantitative PCR, and whole-cell fluorescence in situ hybridization. A much higher proportion of marine crenarchaeota group I within the microbial community was detected in deep-sea hydrothermal environments than in normal deep and surface seawaters. The highest proportion was always obtained from the ambient seawater adjacent to hydrothermal emissions and chimneys but not from the hydrothermal plumes. These profiles were markedly different from the profiles of epsilon-Proteobacteria, which are abundant in the low temperatures of deep-sea hydrothermal environments.     

Microbial diversity of a sulfide black smoker in main endeavour hydrothermal vent field,Juan de Fuca Ridge

Submarine hydrothermal vents are among the least-understood habitats on Earth but have been the intense focus of research in the past 30 years. An active hydrothermal sulfide chimney collected from the Dudley site in the Main Endeavour vent Field (MEF) of Juan de Fuca Ridge was investigated using mineralogical and molecular approaches. Mineral analysis indicated that the chimney was composed mainly of Fe-, Zn-and Cu-rich sulfides. According to phylogenetic analysis, within the Crenarchaeota, clones of the order Desulfurococcales predominated, comprising nearly 50% of archaeal clones. Euryarchaeota were composed mainly of clones belonging to Thermococcales and deep-sea hydrothermal vent Euryarchaeota (DHVE), each of which accounted for about 20% of all clones. Thermophilic or hyperthermophilic physiologies were common to the predominant archaeal groups. More than half of bacterial clones belonged to ɛ-Proteobacteria, which confirmed their prevalence in hydrothermal vent environments. Clones of Proteobacteria (γ-, δ-, β-), Cytophaga-Flavobacterium-Bacteroides (CFB) and Deinococcus-Thermus occurred as well. It was remarkable that methanogens and methanotrophs were not detected in our 16S rRNA gene library. Our results indicated that sulfur-related metabolism, which included sulfur-reducing activity carried out by thermophilic archaea and sulfur-oxidizing by mesophilic bacteria, was common and crucial to the vent ecosystem in Dudley hydrothermal site.     

Metagenomic resolution of microbial functions in deep-sea hydrothermal plumes across the Eastern Lau Spreading Center

Microbial processes within deep-sea hydrothermal plumes affect ocean biogeochemistry on global scales. In rising hydrothermal plumes, a combination of microbial metabolism and particle formation processes initiate the transformation of reduced chemicals like hydrogen sulfide, hydrogen, methane, iron, manganese and ammonia that are abundant in hydrothermal vent fluids. Despite the biogeochemical importance of this rising portion of plumes, it is understudied in comparison to neutrally buoyant plumes. Here we use metagenomics and bioenergetic modeling to describe the abundance and genetic potential of microorganisms in relation to available electron donors in five different hydrothermal plumes and three associated background deep-sea waters from the Eastern Lau Spreading Center located in the Western Pacific Ocean. Three hundred and thirty one distinct genomic ‘bins'' were identified, comprising an estimated 951 genomes of archaea, bacteria, eukarya and viruses. A significant proportion of these genomes is from novel microorganisms and thus reveals insights into the energy metabolism of heretofore unknown microbial groups. Community-wide analyses of genes encoding enzymes that oxidize inorganic energy sources showed that sulfur oxidation was the most abundant and diverse chemolithotrophic microbial metabolism in the community. Genes for sulfur oxidation were commonly present in genomic bins that also contained genes for oxidation of hydrogen and methane, suggesting metabolic versatility in these microbial groups. The relative diversity and abundance of genes encoding hydrogen oxidation was moderate, whereas that of genes for methane and ammonia oxidation was low in comparison to sulfur oxidation. Bioenergetic-thermodynamic modeling supports the metagenomic analyses, showing that oxidation of elemental sulfur with oxygen is the most dominant catabolic reaction in the hydrothermal plumes. We conclude that the energy metabolism of microbial communities inhabiting rising hydrothermal plumes is dictated by the underlying plume chemistry, with a dominant role for sulfur-based chemolithoautotrophy.     

Predicting the response of the deep-ocean microbiome to geochemical perturbations by hydrothermal vents

Submarine hydrothermal vents perturb the deep-ocean microbiome by injecting reduced chemical species into the water column that act as an energy source for chemosynthetic organisms. These systems thus provide excellent natural laboratories for studying the response of microbial communities to shifts in marine geochemistry. The present study explores the processes that regulate coupled microbial-geochemical dynamics in hydrothermal plumes by means of a novel mathematical model, which combines thermodynamics, growth and reaction kinetics, and transport processes derived from a fluid dynamics model. Simulations of a plume located in the ABE vent field of the Lau basin were able to reproduce metagenomic observations well and demonstrated that the magnitude of primary production and rate of autotrophic growth are largely regulated by the energetics of metabolisms and the availability of electron donors, as opposed to kinetic parameters. Ambient seawater was the dominant source of microbes to the plume and sulphur oxidisers constituted almost 90% of the modelled community in the neutrally-buoyant plume. Data from drifters deployed in the region allowed the different time scales of metabolisms to be cast in a spatial context, which demonstrated spatial succession in the microbial community. While growth was shown to occur over distances of tens of kilometers, microbes persisted over hundreds of kilometers. Given that high-temperature hydrothermal systems are found less than 100 km apart on average, plumes may act as important vectors between different vent fields and other environments that are hospitable to similar organisms, such as oil spills and oxygen minimum zones.     

Energy landscapes shape microbial communities in hydrothermal systems on the Arctic Mid-Ocean Ridge

Methods developed in geochemical modelling combined with recent advances in molecular microbial ecology provide new opportunities to explore how microbial communities are shaped by their chemical surroundings. Here, we present a framework for analyses of how chemical energy availability shape chemotrophic microbial communities in hydrothermal systems through an investigation of two geochemically different basalt-hosted hydrothermal systems on the Arctic Mid-Ocean Ridge: the Soria Moria Vent field (SMVF) and the Loki''s Castle Vent Field (LCVF). Chemical energy landscapes were evaluated through modelling of the Gibbs energy from selected redox reactions under different mixing ratios between seawater and hydrothermal fluids. Our models indicate that the sediment-influenced LCVF has a much higher potential for both anaerobic and aerobic methane oxidation, as well as aerobic ammonium and hydrogen oxidation, than the SMVF. The modelled energy landscapes were used to develop microbial community composition models, which were compared with community compositions in environmental samples inside or on the exterior of hydrothermal chimneys, as assessed by pyrosequencing of partial 16S rRNA genes. We show that modelled microbial communities based solely on thermodynamic considerations can have a high predictive power and provide a framework for analyses of the link between energy availability and microbial community composition.     

Microbial Community Stratification Controlled by the Subseafloor Fluid Flow and Geothermal Gradient at the Iheya North Hydrothermal Field in the Mid-Okinawa Trough (Integrated Ocean Drilling Program Expedition 331)

The impacts of lithologic structure and geothermal gradient on subseafloor microbial communities were investigated at a marginal site of the Iheya North hydrothermal field in the Mid-Okinawa Trough. Subsurface marine sediments composed of hemipelagic muds and volcaniclastic deposits were recovered through a depth of 151 m below the seafloor at site C0017 during Integrated Ocean Drilling Program Expedition 331. Microbial communities inferred from 16S rRNA gene clone sequencing in low-temperature hemipelagic sediments were mainly composed of members of the Chloroflexi and deep-sea archaeal group. In contrast, 16S rRNA gene sequences of marine group I Thaumarchaeota dominated the microbial phylotype communities in the coarse-grained pumiceous gravels interbedded between the hemipelagic sediments. Based on the physical properties of sediments such as temperature and permeability, the porewater chemistry, and the microbial phylotype compositions, the shift in the physical properties of the sediments is suggested to induce a potential subseafloor recharging flow of oxygenated seawater in the permeable zone, leading to the generation of variable chemical environments and microbial communities in the subseafloor habitats. In addition, the deepest section of sediments under high-temperature conditions (∼90°C) harbored the sequences of an uncultivated archaeal lineage of hot water crenarchaeotic group IV that may be associated with the high-temperature hydrothermal fluid flow. These results indicate that the subseafloor microbial community compositions and functions at the marginal site of the hydrothermal field are highly affected by the complex fluid flow structure, such as recharging seawater and underlying hydrothermal fluids, coupled with the lithologic transition of sediments.     

Characterization of Bacterial Communities in Deep-Sea Hydrothermal Vents from Three Oceanic Regions

Deep-sea hydrothermal vents are considered to be one of the most spectacular ecosystems on Earth. Microorganisms form the basis of the food chain in vents controlling the vent communities. However, the diversity of bacterial communities in deep-sea hydrothermal vents from different oceans remains largely unknown. In this study, the pyrosequencing of 16S rRNA gene was used to characterize the bacterial communities of the venting sulfide, seawater, and tubeworm trophosome from East Pacific Rise, South Atlantic Ridge, and Southwest Indian Ridge, respectively. A total of 23,767 operational taxonomic units (OTUs) were assigned into 42 different phyla. Although Proteobacteria, Actinobacteria, and Bacteroidetes were the predominant phyla in all vents, differences of bacterial diversity were observed among different vents from three oceanic regions. The sulfides of East Pacific Rise possessed the most diverse bacterial communities. The bacterial diversities of venting seawater were much lower than those of vent sulfides. The symbiotic bacteria of tubeworm Ridgeia piscesae were included in the bacterial community of vent sulfides, suggesting their significant ecological functions as the primary producers in the deep-sea hydrothermal vent ecosystems. Therefore, our study presented a comprehensive view of bacterial communities in deep-sea hydrothermal vents from different oceans.     

Relationships between microbial community structure and hydrochemistry in a landfill leachate-polluted aquifer

Knowledge about the relationship between microbial community structure and hydrogeochemistry (e.g., pollution, redox and degradation processes) in landfill leachate-polluted aquifers is required to develop tools for predicting and monitoring natural attenuation. In this study analyses of pollutant and redox chemistry were conducted in parallel with culture-independent profiling of microbial communities present in a well-defined aquifer (Banisveld, The Netherlands). Degradation of organic contaminants occurred under iron-reducing conditions in the plume of pollution, while upstream of the landfill and above the plume denitrification was the dominant redox process. Beneath the plume iron reduction occurred. Numerical comparison of 16S ribosomal DNA (rDNA)-based denaturing gradient gel electrophoresis (DGGE) profiles of Bacteria and Archaea in 29 groundwater samples revealed a clear difference between the microbial community structures inside and outside the contaminant plume. A similar relationship was not evident in sediment samples. DGGE data were supported by sequencing cloned 16S rDNA. Upstream of the landfill members of the beta subclass of the class Proteobacteria (beta-proteobacteria) dominated. This group was not encountered beneath the landfill, where gram-positive bacteria dominated. Further downstream the contribution of gram-positive bacteria to the clone library decreased, while the contribution of delta-proteobacteria strongly increased and beta-proteobacteria reappeared. The beta-proteobacteria (Acidovorax, Rhodoferax) differed considerably from those found upstream (Gallionella, Azoarcus). Direct comparisons of cloned 16S rDNA with bands in DGGE profiles revealed that the data from each analysis were comparable. A relationship was observed between the dominant redox processes and the bacteria identified. In the iron-reducing plume members of the family Geobacteraceae made a strong contribution to the microbial communities. Because the only known aromatic hydrocarbon-degrading, iron-reducing bacteria are Geobacter spp., their occurrence in landfill leachate-contaminated aquifers deserves more detailed consideration.     

Comparative analysis between protist communities from the deep‐sea pelagic ecosystem and specific deep hydrothermal habitats

Protist communities associated with deep seawater and bivalves from six hydrothermal sites in the Pacific Ocean were characterized by microscopy and molecular rRNA gene surveys (18S rRNA) and compared with planktonic communities from Pacific deep‐pelagic seawater (from 500 to 3000 m in depth). Genetic libraries from larger size fractions (> 3 µm) of deep‐pelagic water were mainly dominated by Dinophyceae, whereas small size fractions (< 3 µm) mainly revealed radiolarians and Syndiniales. In contrast, more specific opportunistic detritivores and grazers, mostly belonging to Stramenopiles and Cercozoa, were detected from water surrounding vent chimneys. Protist communities were different in the pallial cavity of the giant hydrothermal bivalves Bathymodiolus thermophilus and Calyptogena magnifica, dominated by Ciliophora (primarily belonging to Phyllopharyngea, Oligohymenophorea and Oligotrichea) and Cercozoa. Interestingly, protist communities retrieved from the pallial cavity liquid of hydrothermal bivalves were remarkably homogeneous along the Southern East Pacific Rise, in contrast to bivalves collected on the Mid‐Atlantic Ridge hydrothermal vents and cold seeps from the Gulf of Mexico. Hence, complex protist communities seem to occur inside hydrothermal bivalves, and these metazoa may constitute a stable micro‐niche for micro‐eukaryotes, including grazers, detritivores, symbionts and potential parasites. From these communities, new lineages within the ciliates may emerge.     

Microbial diversity of Loki's Castle black smokers at the Arctic Mid‐Ocean Ridge

Hydrothermal vent systems harbor rich microbial communities ranging from aerobic mesophiles to anaerobic hyperthermophiles. Among these, members of the archaeal domain are prevalent in microbial communities in the most extreme environments, partly because of their temperature‐resistant and robust membrane lipids. In this study, we use geochemical and molecular microbiological methods to investigate the microbial diversity in black smoker chimneys from the newly discovered Loki's Castle hydrothermal vent field on the Arctic Mid‐Ocean Ridge (AMOR) with vent fluid temperatures of 310–320 °C and pH of 5.5. Archaeal glycerol dialkyl glycerol tetraether lipids (GDGTs) and H‐shaped GDGTs with 0–4 cyclopentane moieties were dominant in all sulfide samples and are most likely derived from both (hyper)thermophilic Euryarchaeota and Crenarchaeota. Crenarchaeol has been detected in low abundances in samples derived from the chimney exterior indicating the presence of Thaumarchaeota at lower ambient temperatures. Aquificales and members of the Epsilonproteobacteria were the dominant bacterial groups detected. Our observations based on the analysis of 16S rRNA genes and biomarker lipid analysis provide insight into microbial communities thriving within the porous sulfide structures of active and inactive deep‐sea hydrothermal vents. Microbial cycling of sulfur, hydrogen, and methane by archaea in the chimney interior and bacteria in the chimney exterior may be the prevailing biogeochemical processes in this system.     

Denaturing gradient gel electrophoresis analyses of the vertical distribution and diversity of Vibrio spp. populations in the Cariaco Basin

The Cariaco system is the second largest permanently anoxic marine water body in the world. Its water column is characterized by a pronounced vertical layering of microbial communities. The goal of our study was to investigate the vertical distribution and diversity of Vibrio spp. present in the Cariaco Basin waters using denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rDNA fragments. Representatives of the Vibrio genus were detected by nested and direct PCR in seawater at 10 depths. Sequence analyses of 55 DGGE bands revealed that only 11 different operational taxonomic units (OTU) are identified as Vibrio species. Between one and five OTUs were detected at each depth and the most common OTUs were OTU 1 and OTU 2, which phylogenetically clustered with Vibrio chagasii and Vibrio fortis, respectively. OTUs 3 and 4 were only found in the anoxic zone and were identified as Vibrio orientalis and Vibrio neptunius, respectively. Several Vibrio species detected are potentially pathogenic to human, prawns and corals such as Vibrio parahaemolyticus, Vibrio fischeri and Vibrio shilonii. In the Cariaco Basin, different Vibrio species were found to be specific to specific depths strata, suggesting that this genus is a natural component of the microbial communities in this marine redox environment.