Molecular microbiological approaches to understand biogeochemical processes in deep aquifers

Naganuma, Takashi; Iwatsuki, Teruki  ; Shimizu, Satoru*; Akiyama, Masaru*; Ishijima, Yoji*

Microbial communities affect geochemical and hydrogeological processes in deep aquifers, and have been characterized mainly by genetic approaches as well as activity measurements. We have analyzed 16S rDNA assemblages from hydrologically isolated aquifers of porous-but-less-permeable strata in the northernmost part of Japan, and revealed distinctive microbial communities including methanogens and so-far-uncultured species. We have also collected 16S rDNA of the 0.2-micron m-passing-but-0.1-micron m-captured microorganisms from sedimentary and granite rock aquifers in a uranium deposit area of central Japan. In situ activities are characterized and measured by culture-based physiological approaches, which have many limitations and biases though. We have developed a quantification of mRNA for redox-responsive proteins of Fe(III)-reducing bacteria collected from a deep aquifer. This approach is applicable to other aquifer processes such as reduction of nitrate, sulfate, CO, etc.