As a deep subsurface biosphere is thought to be the biggest biosphere in the earth, it is very interesting to know the phylogenetic and functional diversity in such environments. However, there is a little biological information for them because it is very hard to recover whole microbial community by only culture-base methods. In that sense, metagenomics is one of major useful methods to elucidate the microbial flora in unknown biosphere, which seems to be constructed by mainly unculturable...