title: Hadal biosphere: insight into the microbial ecosystem in the deepest ocean on Earth.
abstract: Hadal oceans at water depths below 6,000 m are the least-explored aquatic biosphere. The Challenger Deep, located in the western equatorial Pacific, with a water depth of ∼11 km, is the deepest ocean on Earth. Microbial communities associated with waters from the sea surface to the trench bottom (0∼10,257 m) in the Challenger Deep were analyzed, and unprecedented trench microbial communities were identified in the hadal waters (6,000∼10,257 m) that were distinct from the abyssal microbial communities. The potentially chemolithotrophic populations were less abundant in the hadal water than those in the upper abyssal waters. The emerging members of chemolithotrophic nitrifiers in the hadal water that likely adapt to the higher flux of electron donors were also different from those in the abyssal waters that adapt to the lower flux of electron donors. Species-level niche separation in most of the dominant taxa was also found between the hadal and abyssal microbial communities. Considering the geomorphology and the isolated hydrotopographical nature of the Mariana Trench, we hypothesized that the distinct hadal microbial ecosystem was driven by the endogenous recycling of organic matter in the hadal waters associated with the trench geomorphology.
authors.affiliation: Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science & Technology, Yokosuka 237-0061, Japan; takuron@jamstec.go.jp.
authors.forename: Takuro
authors.initials: T
authors.lastname: Nunoura
authors.affiliation: Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science & Technology, Yokosuka 237-0061, Japan; Department of Subsurface Geobiological Analysis and Research and.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Takaki
authors.affiliation: Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science & Technology, Yokosuka 237-0061, Japan;
authors.forename: Miho
authors.initials: M
authors.lastname: Hirai
authors.affiliation: Department of Subsurface Geobiological Analysis and Research and.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shimamura
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan; Department of Environmental Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8502, Japan;
authors.forename: Akiko
authors.initials: A
authors.lastname: Makabe
authors.affiliation: Research and Development Center for Marine Biosciences, Japan Agency for Marine-Earth Science & Technology, Yokosuka 237-0061, Japan;
authors.forename: Osamu
authors.initials: O
authors.lastname: Koide
authors.affiliation: Graduate School of Nanobioscience, Yokohama City University, Kanazawa-ku, Yokohama 236-0027, Japan; and.
authors.forename: Tohru
authors.initials: T
authors.lastname: Kikuchi
authors.affiliation: Department of Subsurface Geobiological Analysis and Research and.
authors.forename: Junichi
authors.initials: J
authors.lastname: Miyazaki
authors.affiliation: Institute of Agriculture, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan;
authors.forename: Keisuke
authors.initials: K
authors.lastname: Koba
authors.affiliation: Department of Environmental Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama 226-8502, Japan;
authors.forename: Naohiro
authors.initials: N
authors.lastname: Yoshida
authors.affiliation: Department of Earth and Planetary Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan.
authors.forename: Michinari
authors.initials: M
authors.lastname: Sunamura
authors.affiliation: Department of Subsurface Geobiological Analysis and Research and.
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
mesh_terms: D001105:Archaea / Q000235:genetics / Q000254:growth & development*; D001419:Bacteria / Q000235:genetics / Q000254:growth & development*; D018534:Earth, Planet; D017753:Ecosystem; D052836:Heterotrophic Processes; D008969:Molecular Sequence Data; D058465:Nitrification; D009792:Oceans and Seas; D011387:Prokaryotic Cells / Q000378:metabolism; D012335:RNA, Ribosomal / Q000235:genetics; D054679:Ribosome Subunits, Small / Q000235:genetics; D054712:Salinity; D013696:Temperature
chemical_list: D012335:RNA, Ribosomal
keywords: Challenger Deep; hadal; niche separation; nitrification; trench