Spatial distribution of microbial populations and carbon cycle in the subsurface environment of the Horonobe area, Hokkaido, Japan

北海道幌延地域の地下環境における微生物群集の空間分布と炭素循環

天野 由記   ; 伊勢 孝太郎; 寺島 元基  ; 佐々木 祥人 ; 雨宮 浩樹; 吉川 英樹

Amano, Yuki; Ise, Kotaro; Terashima, Motoki; Sasaki, Yoshito; Amamiya, Hiroki; Yoshikawa, Hideki

天然バリア中の核種移行に関わる不確実性要因となりうる微生物影響評価の観点から、幌延地下施設を利用して地下環境における微生物群集の空間分布について調査を実施した。その結果、微生物分布は酸化還元状態や炭素源のような地球化学条件と密接に関連していることが示された。

Microorganisms are widely distributed in the subsurface environments. However, the distribution, role and rate of metabolisms, and the origin of the activity are not well known. In this study, we investigated deep groundwater samples of sedimentary rocks, which is contained supersuturated methane and carbon dioxide, using boreholes in the Horonobe Underground Research Laboratory (URL), in the northern part of Hokkaido, Japan. Abundant methanogens were detected in the groundwater, and 80% of them were related to Methanoregula boonei and Methanobacterium flexile that can utilize hydrogen and carbon dioxide as methanogenesis. Phylotypes clustered within the phylum Firmicutes, beta-Proteobacteria, delta-Proteobacteria and Candidatte division TM7 were dominant in the groundwater samples. Laboratory experiment using culture a technique showed that humic substances purified from Horonobe area could be degraded by microorganisms. Our results suggest that microbial spatial distribution in the subsurface environment was correlate closely with geochemical conditions, such as redox condition and carbon sources.