Drilling effect on subsurface microbial community structure in groundwater from the -250 m gallery at the Horonobe Underground Research Laboratory, Japan

Ise, Kotaro; Amano, Yuki   ; Sasaki, Yoshito ; Yoshikawa, Hideki

We investigated the changes in geochemical and microbial characteristics by using molecular techniques to characterize subsurface microbial community structure response toward oxygen intrusion. Therefore we collected groundwater samples from a borehole at -250 m gallery of Horonobe Underground Research Laboratory. The first sampling was conducted right after the borehole was drilled. In this sample, -Proteobacteria dominated and accounted for 65% of total clone library. All these -Proteobacteria clones are closely related to spp. which is known as sulfide oxidizer and which can growth chemoautrophically. And after two years, the microbial structure was drastically changed and most detected clones were uncultured species such as candidate division WS6, JS1 relatives which are frequently detected in deep-sea sediments.