Microbial Community of a Hydrothermal Mud Vent Underneath the Deep-Sea Anoxic Brine Lake Urania (Eastern Mediterranean) |
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Authors: | Michail M Yakimov Laura Giuliano Simone Cappello Renata Denaro Peter N Golyshin |
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Institution: | (1) Istituto per l’Ambiente Marino Costiero, CNR, Spianata S. Raineri, 86, 98122 Messina, Italy;(2) Technical University Braunschweig, 38106 Braunschweig, Germany |
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Abstract: | 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. |
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Keywords: | deep-sea hypersaline anoxic basins hydrothermal mud fluids 16S rRNA microbial community structure and function |
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