The Succession of bacterial community structure in groundwater from a 250-m gallery in the Horonobe Underground Research Laboratory

Ise, Kotaro; Sasaki, Yoshito ; Amano, Yuki   ; Iwatsuki, Teruki  ; Nanjo, Isao*; Asano, Takahiro*; Yoshikawa, Hideki

We investigated the change in bacterial community structure after drilling boreholes, 09-V250-M02 and 09-V250-M03 in the 250 m depth research gallery of Horonobe Underground Research Laboratory (URL). In 09-V250-M02, -Proteobacteria was predominantly detected in the clone library analyses of the groundwater samples conducted immediately after drilling the borehole. All these -Proteobacteria clones are closely related to . which is known as sulfide oxidizing chemoautotrophic bacteria. After four years, the microbial structure was drastically changed and most detected OTUs were uncultured species such as candidate division OP9 and Chloroflexi relatives which are frequently detected in deep-sea sediments.