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Assimilation of methane and inorganic carbon by microbial communities mediating the anaerobic oxidation of methane

Authors

  • Gunter Wegener,

    Corresponding author
    1. Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany.
      *E-mail gwegener@mpi-bremen.de; Tel. (+49) 421 2028 877; Fax (+49) 421 2028 690.
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  • Helge Niemann,

    1. Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany.
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    • Present address: Institute for Environmental Geosciences, University of Basel, Bernoullistr. 30, 4056 Basel, Switzerland.

  • Marcus Elvert,

    1. Research Center Ocean Margins, University of Bremen, Leobener Str., 28359 Bremen, Germany.
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  • Kai-Uwe Hinrichs,

    1. Research Center Ocean Margins, University of Bremen, Leobener Str., 28359 Bremen, Germany.
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  • Antje Boetius

    1. Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany.
    2. Jacobs University Bremen gGmbH, Campusring 1, 28759 Bremen, Germany.
    3. Alfred Wegener Institute for Polar and Marine Research, 27515 Bremerhaven, Germany.
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*E-mail gwegener@mpi-bremen.de; Tel. (+49) 421 2028 877; Fax (+49) 421 2028 690.

Summary

The anaerobic oxidation of methane (AOM) is a major sink for methane on Earth and is performed by consortia of methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB). Here we present a comparative study using in vitro stable isotope probing to examine methane and carbon dioxide assimilation into microbial biomass. Three sediment types comprising different methane-oxidizing communities (ANME-1 and -2 mixture from the Black Sea, ANME-2a from Hydrate Ridge and ANME-2c from the Gullfaks oil field) were incubated in replicate flow-through systems with methane-enriched anaerobic seawater medium for 5–6 months amended with either 13CH4 or H13CO3-. In all three sediment types methane was anaerobically oxidized in a 1:1 stoichiometric ratio compared with sulfate reduction. Similar amounts of 13CH4 or 13CO2 were assimilated into characteristic archaeal lipids, indicating a direct assimilation of both carbon sources into ANME biomass. Specific bacterial fatty acids assigned to the partner SRB were almost exclusively labelled by 13CO2, but only in the presence of methane as energy source and not during control incubations without methane. This indicates an autotrophic growth of the ANME-associated SRB and supports previous hypotheses of an electron shuttle between the consortium partners. Carbon assimilation efficiencies of the methanotrophic consortia were low, with only 0.25–1.3 mol% of the methane oxidized.

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