The Effect of Methane on The Microbial Community in The Sediment of Ulleung-Basin

Abstract

Geophysical survey has shown that gas hydrate exists in deep-sea sediments at a water depth of 2,000 m in the East Sea, Korea. Bacterial community analysis in methane hydrate-bearing deep-sea sediments (ca. 8 m below the seafloor) obtained from the Ulleung-Basin was made by cultivation-independent techniques, terminal restriction fragment length polymorphism (T-RFLP) and 16S rDNA pyrosequencing. In the T-RFLP analysis, it was shown that the community structure in the possible sulfate methane transition zone (SMTZ) that was characterized as depleted sulfate and increased methane, was different from that of the upper and deeper region of the SMTZ. And then, 16S rDNA pyrosequencing analsys has been conducted to show the bacterial community structures in high-resolution. Among the total 364,000 sequences, about 180,000 reads were sorted and analysed. The homology searches revealed that the most of those sequences, more than 50% affiliated into the Chloroflexi and candidate division JS1, which were characteristic in the deep-sea marine sediments containing methane hydrate and that the proportion of sequences within δ-proteobacteria was relatively higher in the SMTZ (100 ∼ 150 cm) and surface region (0∼20 cm). This result implied that microbial community structure in the SMTZ characteristic in microbial community structure.