TY - JOUR A1 - D'Hondt, Steven A1 - Spivack, Arthur J. A1 - Pockalny, Robert A1 - Ferdelman, Timothy G. A1 - Fischer, Jan P. A1 - Kallmeyer, Jens A1 - Abrams, Lewis J. A1 - Smith, David C. A1 - Graham, Dennis A1 - Hasiuk, Franciszek A1 - Schrum, Heather A1 - Stancin, Andrea M. T1 - Subseafloor sedimentary life in the South Pacific Gyre N2 - The low-productivity South Pacific Gyre (SPG) is Earth's largest oceanic province. Its sediment accumulates extraordinarily slowly (0.1-1 m per million years). This sediment contains a living community that is characterized by very low biomass and very low metabolic activity. At every depth in cored SPG sediment, mean cell abundances are 3 to 4 orders of magnitude lower than at the same depths in all previously explored subseafloor communities. The net rate of respiration by the subseafloor sedimentary community at each SPG site is 1 to 3 orders of magnitude lower than the rates at previously explored sites. Because of the low respiration rates and the thinness of the sediment, interstitial waters are oxic throughout the sediment column in most of this region. Consequently, the sedimentary community of the SPG is predominantly aerobic, unlike previously explored subseafloor communities. Generation of H-2 by radiolysis of water is a significant electron-donor source for this community. The per-cell respiration rates of this community are about 2 orders of magnitude higher (in oxidation/reduction equivalents) than in previously explored anaerobic subseafloor communities. Respiration rates and cell concentrations in subseafloor sediment throughout almost half of the world ocean may approach those in SPG sediment. Y1 - 2009 UR - http://www.pnas.org/ U6 - https://doi.org/10.1073/pnas.0811793106 SN - 0027-8424 ER - TY - GEN A1 - Adhikari, Rishi Ram A1 - Glombitza, Clemens A1 - Nickel, Julia C. A1 - Anderson, Chloe H. A1 - Dunlea, Ann G. A1 - Spivack, Arthur J. A1 - Murray, Richard W. A1 - D’Hondt, Steven A1 - Kallmeyer, Jens T1 - Hydrogen utilization potential in subsurface sediments T2 - Frontiers in microbiology N2 - Subsurface microbial communities undertake many terminal electron-accepting processes, often simultaneously. Using a tritium-based assay, we measured the potential hydrogen oxidation catalyzed by hydrogenase enzymes in several subsurface sedimentary environments (Lake Van, Barents Sea, Equatorial Pacific, and Gulf of Mexico) with different predominant electron-acceptors. Hydrogenases constitute a diverse family of enzymes expressed by microorganisms that utilize molecular hydrogen as a metabolic substrate, product, or intermediate. The assay reveals the potential for utilizing molecular hydrogen and allows qualitative detection of microbial activity irrespective of the predominant electron-accepting process. Because the method only requires samples frozen immediately after recovery, the assay can be used for identifying microbial activity in subsurface ecosystems without the need to preserve live material. We measured potential hydrogen oxidation rates in all samples from multiple depths at several sites that collectively span a wide range of environmental conditions and biogeochemical zones. Potential activity normalized to total cell abundance ranges over five orders of magnitude and varies, dependent upon the predominant terminal electron acceptor. Lowest per-cell potential rates characterize the zone of nitrate reduction and highest per-cell potential rates occur in the methanogenic zone. Possible reasons for this relationship to predominant electron acceptor include (i) increasing importance of fermentation in successively deeper biogeochemical zones and (ii) adaptation of H(2)ases to successively higher concentrations of H-2 in successively deeper zones. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 447 KW - hydrogenase KW - tritium assay KW - deep biosphere KW - microbial activity KW - Lake Van KW - Barents Sea KW - Equatorial Pacific KW - Gulf of Mexico Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-407678 ER - TY - JOUR A1 - Adhikari, Rishi Ram A1 - Glombitza, Clemens A1 - Nickel, Julia C. A1 - Anderson, Chloe H. A1 - Dunlea, Ann G. A1 - Spivack, Arthur J. A1 - Murray, Richard W. A1 - Kallmeyer, Jens T1 - Hydrogen Utilization Potential in Subsurface Sediments JF - Frontiers in microbiology N2 - Subsurface microbial communities undertake many terminal electron-accepting processes, often simultaneously. Using a tritium-based assay, we measured the potential hydrogen oxidation catalyzed by hydrogenase enzymes in several subsurface sedimentary environments (Lake Van, Barents Sea, Equatorial Pacific, and Gulf of Mexico) with different predominant electron-acceptors. Hydrogenases constitute a diverse family of enzymes expressed by microorganisms that utilize molecular hydrogen as a metabolic substrate, product, or intermediate. The assay reveals the potential for utilizing molecular hydrogen and allows qualitative detection of microbial activity irrespective of the predominant electron-accepting process. Because the method only requires samples frozen immediately after recovery, the assay can be used for identifying microbial activity in subsurface ecosystems without the need to preserve live material. We measured potential hydrogen oxidation rates in all samples from multiple depths at several sites that collectively span a wide range of environmental conditions and biogeochemical zones. Potential activity normalized to total cell abundance ranges over five orders of magnitude and varies, dependent upon the predominant terminal electron acceptor. Lowest per-cell potential rates characterize the zone of nitrate reduction and highest per-cell potential rates occur in the methanogenic zone. Possible reasons for this relationship to predominant electron acceptor include (i) increasing importance of fermentation in successively deeper biogeochemical zones and (ii) adaptation of H(2)ases to successively higher concentrations of H-2 in successively deeper zones. KW - hydrogenase KW - tritium assay KW - deep biosphere KW - microbial activity KW - Lake Van KW - Barents Sea KW - Equatorial Pacific KW - Gulf of Mexico Y1 - 2016 U6 - https://doi.org/10.3389/fmicb.2016.00008 SN - 1664-302X VL - 7 PB - Frontiers Research Foundation CY - Lausanne ER -