5:15 PM - 6:30 PM
[MIS09-P20] Investigation microbial community for gas-hydrate site off-Sakhalin Island
Molecular composition ratio C1/C2+C3 below SMI were in the range between 116 and 225, while d13C and dD values of methane were in the range of -48.9 and -45.7 permil, and of -165 and -149 permil, respectively. These results indicated that the gas compose of large amount of thermogenic gas and small amount of microbial gas.
Forty two individual clones have successfully analyzed, until we submit this article. Three Aciduliprofundum related clones, and three Methanobrevibacter related clones were detected. These sequences were clustered into oceanic methanogen in the phylum Euriarcheota. This result implied that these archaeon generate microbial methane in the core, and may correspond to decrease isotopic 13C ratio of methane and increase the C1/C2+C3 ratio. Slight amount of sequence in Crenarcheota, which may be involved anaerobic methane oxidation (annamox). Interestingly, heterotorophic bacteria in cluster of Deharococcoidetes-related Chroloflexi, of Candidatus artibacteria (named as division JS1/OP9), and of Planctomycetes were frequently widespread in the core. The phylum Chloroflexi is a lineage for which the class ‘Dehalococcoidetes’ was proposed to accommodate the tetrachloroethane respiring coccus Deharococcides (1). These bacteria may contribute to decomposition of difficultly degradable organic matters accumulated on deep sea floor. Planctomycetes have been often detected, and widespread in methane-seep (2), but the functional characters have been unknown. Recently, candidatus artibacteria have been revealed to play significant role as synbiotropic scavenger in artificial methanogenic bioreactor, by using single cell genome analysis (3). According to the study, atribacteria may support methanogen and chloroflexi through the by-product generation such as acetate, butyrate, and H2. These results implied that thermogenic and microbial mixed-derived gas composition may be formed by symbiotic metabolism of those species, but not simply generated from inorganic gases such as CO2 and H2 by methanogen.
1)Maymo-Gatell, X., Chien Y., Gossett J. M., Zinder S. H. (1997) Isolation of bacterium that reductively dechlorinates tetrachloroethane to ethane. Science 276: 1568-1571.
2)Yanagawa K., Kouduka M., Hachikubo A., Tomaru H., Suzuki Y. (2014) Distinct microbial communities thriving in gas hydrate-associated sediments from the eastern Japan Sea. J Asia. Ear. Sci. 90: 243-249.
3)Nobu M. K., Narihiro T., Rinke C., Kamagata Y., Tringe S. G., Woyke T. Liu W-T (2015) Microbial dark matter ecogenomics reveals complex synergistic networks in a methanogenic bioreactor. ISME J. 9: 1710-1722.