title: Molecular biological and isotopic biogeochemical prognoses of the nitrification-driven dynamic microbial nitrogen cycle in hadopelagic sediments.
abstract: There has been much progress in understanding the nitrogen cycle in oceanic waters including the recent identification of ammonia-oxidizing archaea and anaerobic ammonia oxidizing (anammox) bacteria, and in the comprehensive estimation in abundance and activity of these microbial populations. However, compared with the nitrogen cycle in oceanic waters, there are fewer studies concerning the oceanic benthic nitrogen cycle. To further elucidate the dynamic nitrogen cycle in deep-sea sediments, a sediment core obtained from the Ogasawara Trench at a water depth of 9760 m was analysed in this study. The profiles obtained for the pore-water chemistry, and nitrogen and oxygen stable isotopic compositions of pore-water nitrate in the hadopelagic sediments could not be explained by the depth segregation of nitrifiers and nitrate reducers, suggesting the co-occurrence of nitrification and nitrate reduction in the shallowest nitrate reduction zone. The abundance of SSU rRNA and functional genes related to nitrification and denitrification are consistent with the co-occurrence of nitrification and nitrate reduction observed in the geochemical analyses. This study presents the first example of cooperation between aerobic and anaerobic nitrogen metabolism in the deep-sea sedimentary environments.
authors.affiliation: Subsurface Geobiology & Advanced Research Project, Extremobiosphere Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science & Technology, 2-15 Natsushima-cho, Yokosuka 237-0061, Japan. takuron@jamstec.go.jp
authors.forename: Takuro
authors.initials: T
authors.lastname: Nunoura
authors.affiliation: Precambrian Ecosystem Laboratory, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Nishizawa
authors.affiliation: Environmental Biosciences, International Graduate School of Arts and Sciences, Yokohama City University, 22-2 Seto, Kanazawa-ku, Yokohama, 236-0027, Japan.
authors.forename: Tohru
authors.initials: T
authors.lastname: Kikuchi
authors.affiliation: Marine Bioresource Exploration Research Team, Marine Biodiversity Research Program, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Taishi
authors.initials: T
authors.lastname: Tsubouchi
authors.affiliation: Subsurface Geobiology & Advanced Research (SUGAR) Project, Extremobiosphere Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Miho
authors.initials: M
authors.lastname: Hirai
authors.affiliation: Soft Matter and Extremophiles Research Team, Extremobiosphere Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Koide
authors.affiliation: Subsurface Geobiology & Advanced Research (SUGAR) Project, Extremobiosphere Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.|Precambrian Ecosystem Laboratory, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Junichi
authors.initials: J
authors.lastname: Miyazaki
authors.affiliation: Subsurface Geobiology & Advanced Research (SUGAR) Project, Extremobiosphere Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Hisako
authors.initials: H
authors.lastname: Hirayama
authors.affiliation: Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo, 183-8509, Japan.
authors.forename: Keisuke
authors.initials: K
authors.lastname: Koba
authors.affiliation: Subsurface Geobiology & Advanced Research (SUGAR) Project, Extremobiosphere Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.|Precambrian Ecosystem Laboratory, Japan Agency for Marine-Earth Science & Technology (JAMSTEC), 2-15 Natsushima-cho, Yokosuka, 237-0061, Japan.
authors.forename: Ken
authors.initials: K
authors.lastname: Takai
mesh_terms: D000641:Ammonia / Q000378:metabolism; D001105:Archaea / Q000235:genetics / Q000378:metabolism*; D001419:Bacteria / Q000235:genetics / Q000378:metabolism*; D058440:Denitrification / Q000235:genetics*; D019015:Geologic Sediments / Q000382:microbiology*; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D058465:Nitrification / Q000235:genetics*; D009584:Nitrogen / Q000378:metabolism; D009792:Oceans and Seas; D010084:Oxidation-Reduction; D010100:Oxygen / Q000378:metabolism; D010802:Phylogeny; D012335:RNA, Ribosomal / Q000235:genetics
chemical_list: D009566:Nitrates; D012335:RNA, Ribosomal; D000641:Ammonia; D009584:Nitrogen; D010100:Oxygen