Earth and Environmental Sciences

Deep sea hydrothermal vent ecosystem
Xiang Xiao, Shanghai Jiao Tong University

Deep-sea hydrothermal vent chimneys are believed to be windows of deep subsphere. They are formed by the chemical interaction between the hot, reduced fluids generated deep within the geothermal system. They are regarded as primordial environments that are reminiscent of early Earth, with reactive gases, dissolved elements, and thermal and chemical gradients that operate over spatial scales of centimeters to meters. These steep chemical and thermal gradients along and inside the sulfide chimneys provide a wide range of microhabitats for chemolithoautotrophic microorganisms which are able to fix inorganic carbon using chemical energy obtained through oxidation of reduced compounds contained in the hydrothermal fluids.
In this study, we integrate cultivation, GeoChip hybridization, clone libraries, and quantitative PCR and pyrosequence approaches to examine the phylogenetic diversity and metabolic diversity of microbial populations present in vent chimneys. Microbial functional genes/populations suggested a rapid change in the microbial community composition during the growth of the chimney. The hydrothermal microbial communities are metabolically and physiologically highly diverse. It was mainly fueled by sulfur oxidation through Sox-dependent and APS -dependent pathways, putatively coupled with denitrification to perform inorganic carbon fixation through the CBB cycle. Noticeably, An isolate Archaea CH1 was unable to grow for pressures below 15 MPa and represents the first obligate piezo-hyperthermophilic organism. By combining the physiological properties of hyperthermophiles and strict piezophiles, CH1 extends the pressure/temperature limits for life. Further CH1 genome analysis may give us more information on its deep subsphere residence, also house keeping genes from early lifes.

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Earth and Environmental Sciences

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