GEOMICROBIOLOGY IN EXTREME ENVIRONMENTS: LINKING GEOLOGICAL PROCESSES WITH MICROBIAL ACTIVITIES

This talk will present an overview of our current research on microbial life in various extreme geological environments. These environments include terrestrial and marine deep subsurface, dry deserts, and saline lakes on the Tibetan Plateau. We employ an integrated approach combining regional tectonics, mineralogy, geochemistry, molecular microbiology and cultivation to delineate mutual interactions between microbial and geological processes. In the deep continental subsurface, novel microbial life is discovered down to 5000 m in ultra-high pressure metamorphic rocks in Chinese continental scientific deep drilling with unique metabolic functions such as iron cycling in solid minerals at a microscopic scale. In the marine subsurface, we seek to understand microbially mediated carbon cycling (oxidation of methane and deposition of carbonates) in gas hydrate deposits in South China Sea. In seemingly barren dry deserts in Atacama and Jordan, signs of life (endolithic cyanobacteria) have been detected to be living in solid substrate gypsum. In saline and hypersaline lakes on the Tibetan Plateau, systematic shifts in microbial community structure are observed from lake water to sediments of varying depth, and these shifts are correlated with mineralogy and geochemistry, such as types of salt mineral (gypsum, halite), salinity, and the redox state. These changes in mineralogy and geochemistry are correlated with regional tectonic, climatic and topographic evolution in this region. Microbial record may be a valuable tool for reconstruction of these geologically significant events. Some isolates from this environment have shown remarkable resistance to UV and gamma radiation, which may be used as analogs for life on Mars and other planets.