Deep Microbial Life in Granitic Aquifer. uncultured microorganism

Deep granitic aquifer is one of the largest, but least-understood, microbial habitats. To avoid drilling contamination from the surface biosphere, underground drilling was conducted for a 300-m deep granitic basement at the Mizunami underground research laboratory (URL) in Japan. At the Mizunami URL, microbial communities colonized in the underground borehole were annually monitored over four years in combination with geochemical investigations. After three years of monitoring at the Mizunami URL, the dominant microbes were shifted from the aerophilic betaproteobacterial contaminant to the potentially indigenous Nitrospirae bacteria. As the dominance of Nitrospirae bacteria was stable over the last two years, pyrosequencing was conducted to obtain a comprehensive view of biodiversity and microbial life possibly being indigenous to deep granitic aquifer.