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Subsurface Microbiology in Japan: Challenging Unseen Majority

 

Ken Takai

Subground Animalculae Retrieval (SUGAR) Project, Deep-sea Microorganisms Research Group, Japan Marine Science & Technology Center

 

Since the discovery of viable microbial population in terrestrial and oceanic subsurface environments, there has been increasing interest in the microorganisms in subsurface environments. The subsurface biosphere is spatially expansive and contains a vast diversity of potential microbial habitats, many of which are at or near the known limits of life. Microorganisms have been found in a variety of extreme subsurface environments such as hot formation water associated with deep oil reservoirs, extremely oligotrophic ground waters in deep crystalline rocks, inside ancient subterranean salt deposits and ultra deep subseafloor sediments. The presence of such extremophiles in the deep subsurface provides justification for a re-evaluation of spatial boundaries and biomass potentials of the global biosphere. In addition, recent progress in subsurface microbilogy has established that subsurface microorganisms may significantly impact subsurface geochemical processes and have novel metabolic properties and potential use for industrial processes, bioremediation, or other biotechnological applications.

One possible calculation has suggested that approx. 80-99% of biomass in the earth is derived from the terrestrial and oceanic subsurface biosphere. The vast biomass in the subsurface biosphere is for the most part based on the expansive space and the microbial community density is likely very low. This might prevent intensive exploration and comprehensive investigation toward unseen majority in this planet.

The subsurface microbiology is still at the very early stage even though some preliminary, but very important results have been obtained from the international research cooperation such as the Ocean Drilling Project (ODP). In Japan, this research field is just beginning but the strong wind of subsurface microbiology is rising. The next generation of the Ocean Drilling Project (OD21) will be largely dependent on the new ocean drilling ship and will be conducted by Japanese scientist. The JAMSTEC (Japan Marine Science & Technology Center) will be the principal institute leading the subsurface microbiology in Japan. We have studied microorganisms in deep-sea hydrothermal vent environments and accumulated knowledge on the deep-sea hydrothermal vent microbiology. The deep-sea hydrothermal vent is considered as a window for the subsurface biosphere. Throughout the hydrothermal vents, the microbial community in the subseafloor will be analyzed. Likewise, the terrestrial hot spring and geothermal electric plant well are the pathways toward the terrestrial subsurface biosphere. We try to approarch the deep, hot subsurface biosphere throughout such hot water pathways. We also start the preliminary study of the subsurface microbiology using several core samples obtained from geothermally inactive, deep-sea sediments and the microbial diversity inside the sedimentary and igneous rocks is under investigation. Here, I introduce the preliminary results of our recent investigation for the subsurface microbiology and discuss the foci of the future study.

 

 

 

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