Japan Geoscience Union Meeting 2015

Presentation information


Symbol B (Biogeosciences) » B-CG Complex & General

[B-CG28] Interrelation between Life, Water, Mineral, and Atmosphere

Tue. May 26, 2015 2:15 PM - 4:00 PM 105 (1F)

Convener:*Fumito Shiraishi(Department of Earth and Planetary Systems Science, Graduate School of Science, Hiroshima University), Tsubasa Otake(Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University), Yohey Suzuki(Graduate School of Science, The University of Tokyo), Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Yuichiro Ueno(Department of Earth and Planetary Sciences, Tokyo Institute of Technology), Takeshi Naganuma(Graduate School of Biosphere Science), Takeshi Kakegawa(Graduate School of Science, Tohoku University), Tadashi Yokoyama(Department of Earth and Space Science, Graduate School of Science, Osaka University), Kentaro Nakamura(Precambrian Ecosystem Laboratory (PEL), Japan Agency for Marine-Earth Science and Technology (JAMSTEC)), Chair:Ken Takai(Extremobiosphere Research Center, Japan Agency for Marine-Earth Science & Technology), Kentaro Nakamura(Department of Systems Innovation, School of Engineering, University of Tokyo)

2:30 PM - 2:45 PM

[BCG28-05] Dense microbial community at the surface of manganese nodule formed in ultra-oligotrophic seafloor

*Fumito SHIRAISHI1, Satoshi MITSUNOBU2, Yuki MORONO3, Katsuhiko SUZUKI3, Fumio INAGAKI3 (1.Hiroshima University, 2.University of Shizuoka, 3.JAMSTEC)

During IODP Exp. 329, manganese nodule was collected from the seafloor of ultra-oligotrophic South Pacific Gyre, and its microbial and chemical characteristics were investigated. This nodule was formed on red pelagic clay, and its chemical composition and depositional fabrics indicated that this nodule was formed by hydrogenesis. Synchrotron analysis (μ-XAFS) showed that this nodule was mainly composed of δ-MnO2 and goethite. Microbotryoidal small protrusions at the nodule surface contained relatively high Fe, although there were some high Mn thin layers. Cu content of manganese nodule was about 0.3%, although it was about 10 times higher than that of surrounding sediment.
SYBR Green I staining was applied for cryo-sections prepared from this nodule sample, and revealed that the microbial cell density at the surface part (about 0.5 mm) was almost three orders of magnitude higher than that of surrounding sediment. Sequencing of 16S rDNA (~1400 bp) indicated that the composition of microbial community (both bacteria and archea) inhabiting in this nodule was different from that of surrounding sediment, showing that manganese nodule provided specific habitat for these microorganisms. Most of recognized bacteria were heterotrophs, and known manganese-oxidizing bacteria were not detected. On the other hand, most of archea were the member of Marine Group I, and the percentage of Nitrosopumilus sp. was especially high at the nodule surface. This organism is ammonia-oxidizing autotrophic archea, and its metabolism requires malticopper oxidase that utilizes Cu as a cofactor.
Although the availability of electron donor is very limited in the seafloor of ultra-oligotrophic South Pacific Gyre, Nitrosopumilus sp. can grow autotrophically even under very low ammonia concentration, and its growth is considered to be stimulated on the Cu-accumulated substances such as manganese nodule. Known manganese-oxidizing microorganisms all possess malticopper oxidase and it has critical roles in manganese oxidation. This fact implies the possibility that Nitrosopumilus sp. may contribute to the formation of manganese nodule.