报告题目： Limits and habitability of subseafloor life in the deep sedimentary biosphere
报 告 ?人：Fumio INAGAKI, Ph.D
Group Leader, Senior Research Scientist,
Geomicrobiology Group, Kochi Institute for Core Sample Research, and Geobio-Engineering and Technology
Group, Submarine Resources Research Project, Japan Agency for Marine-Earth Science & Technology
(JAMSTEC), Monobe B200, Nankoku 783-8502, Kochi, Japan.
报告时间：6月20日 上午 10：30
Deep drilling of marine subsurface offers unique opportunities to explore how life persists and evolves in the Earth’s interior ecosystems. The Integrated Ocean Drilling Program (IODP) Expeditions 329 and 337 were the microbiology and biogeochemistry-dedicated scientific ocean drilling, targeting on very distinct oceanographic locations; i.e., in 2010, using the JOIDES Resolution, Expedition 329 explored deep-water sediments (water depth: >5,000 m) down to the basement at 7 sites in the ultra-oligotrophic South Pacific Gyre, whereas during Expedition 337 in 2012, the Chikyu explored ultra-deep sediments (sediment depth: ~2,466 m below seafloor) associated with deeply buried coalbeds in the northwestern Pacific coast. The samples and data collected during these drilling expeditions, as well as rapid technological developments, provide unprecedented opportunities to study the limits and habitability of life in the subseafloor sedimentary biosphere. The number of microbial cells is measured by newly developed cell separation and fluorescent image-based cell count techniques, revealing that cell abundances in both ultra-oligotrophic and deep coalbed-associated sediment samples are several orders of magnitude lower than those previously observed in the Pacific margin sediments. The finding of very small microbial populations that inhabit two distinct extreme subseafloor conditions leads to subsequent questions: What are the environmental constraints for habitability of subseafloor life? What are ecological roles of subseafloor microbial activity in biogeochemical carbon and other elemental cycles? What are genetic and metabolic functions and its diversity of microbial communities? How and why can they live in such deep and extremely energy-limited conditions?