Geomicrobiological properties of ultra-deep granitic groundwater from the Mizunami Underground Research Laboratory (MIU), Central Japan

Fukuda, Akari*; Hagiwara, Hiroki  ; Ishimura, Toyoho*; Kozuka, Mariko*; Ioka, Seiichiro*; Amano, Yuki   ; Tsunogai, Urumu*; Suzuki, Yohei*; Mizuno, Takashi   

To better understand the geochemical and microbiological relationships, we characterized granitic groundwater collected from a 1,148 to 1,169 -m deep borehole interval at the Mizunami Underground Research Laboratory site, Japan, in 2005 and 2008. Geochemical analyses of the groundwater samples indicated that major electron acceptors, such as NO and SO, were not abundant, while dissolved organic carbon (not including organic acids), CH and H were moderately rich. The most common phylotypes were both related to spp., the cultivated members of which can utilize minor electron donors, such as aromatic and aliphatic hydrocarbons. Geomicrobiological results suggest that deep granitic groundwater has been stably colonized by spp. probably owing to the limitation of O, NO and organic acids.