| Cold seeps are characterized by the seepage of fluids and elevated concentration of hydrocarbon (methane mainly), sulfide and carbon dioxide. Geological structure and/or pressure gradient conduce to the seepage. The characterization of microbial communities within sediment from cold seep is essential to understand physiologies of some novel groups and contributions of microbial activities in the extreme environment.We studied on a sediment core sample from the Okhotsk Sea. Total genomic DNA was extracted from 6 layers of 11 and 16S rDNA clone libraries were constructed to investigate the composition of bacterial and archaeal communities combining the surveys of environmental factors such as total organic carbon, total nitrogen and sulfur. Results revealed that both bacterial and archaeal communities displayed diversified composition and clearly stratified distribution:Clones of bacterial communities were from 10 bacterial phyla and some were unclassified sequences. Chloroflexi, candidate division JS1,γ-,δ- proteobacteria were the predominant groups and members of Planctomycetes, candidate division OP8, Actinobacteria, Acidobacteria, Bacteroidetes, Verrucomicrobia were also found in our sample. Additionally, we found SRB (sulfate-reduction bacteria) with a percentage more than 15% in the library of topmost layer which strongly suggest the geochemical process AOM (Anerobic oxidation of methane).Clones of archaeal libraries were mainly divided into six groups: DSAG, MBG-D, MCG, MGI, MBG-A and MHVG. Along the sediment core, the percentage of MBG-D showed obvious relevance with concentration of sulfur, which gives us the suggestion that the group MBG-D may participate in sulfur-related geochemical process in sediment environment in the Okhotsk Sea. |
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