title: Assimilation of methane and inorganic carbon by microbial communities mediating the anaerobic oxidation of methane.
abstract: 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 (13)CH(4) or H(13)CO(3)(-). In all three sediment types methane was anaerobically oxidized in a 1:1 stoichiometric ratio compared with sulfate reduction. Similar amounts of (13)CH(4) or (13)CO(2) 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 (13)CO(2), 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.
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany. gwegener@mpi-bremen.de
authors.forename: Gunter
authors.initials: G
authors.lastname: Wegener
authors.forename: Helge
authors.initials: H
authors.lastname: Niemann
authors.forename: Marcus
authors.initials: M
authors.lastname: Elvert
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Hinrichs
authors.forename: Antje
authors.initials: A
authors.lastname: Boetius
mesh_terms: D000693:Anaerobiosis; D001105:Archaea / Q000378:metabolism*; D052818:Autotrophic Processes; D018533:Biomass; D019149:Bioreactors; D017554:Carbon Compounds, Inorganic / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism; D017753:Ecosystem; D004734:Energy Metabolism; D005227:Fatty Acids / Q000096:biosynthesis; D019015:Geologic Sediments / Q000382:microbiology; D008697:Methane / Q000378:metabolism*; D010084:Oxidation-Reduction; D012623:Seawater / Q000382:microbiology; D016999:Sulfur-Reducing Bacteria / Q000378:metabolism*
chemical_list: D017554:Carbon Compounds, Inorganic; D002247:Carbon Isotopes; D005227:Fatty Acids; D002245:Carbon Dioxide; D008697:Methane