title: Autotrophy as a predominant mode of carbon fixation in anaerobic methane-oxidizing microbial communities.
abstract: The methane-rich, hydrothermally heated sediments of the Guaymas Basin are inhabited by thermophilic microorganisms, including anaerobic methane-oxidizing archaea (mainly ANME-1) and sulfate-reducing bacteria (e.g., HotSeep-1 cluster). We studied the microbial carbon flow in ANME-1/ HotSeep-1 enrichments in stable-isotope-probing experiments with and without methane. The relative incorporation of (13)C from either dissolved inorganic carbon or methane into lipids revealed that methane-oxidizing archaea assimilated primarily inorganic carbon. This assimilation is strongly accelerated in the presence of methane. Experiments with simultaneous amendments of both (13)C-labeled dissolved inorganic carbon and deuterated water provided further insights into production rates of individual lipids derived from members of the methane-oxidizing community as well as their carbon sources used for lipid biosynthesis. In the presence of methane, all prominent lipids carried a dual isotopic signal indicative of their origin from primarily autotrophic microbes. In the absence of methane, archaeal lipid production ceased and bacterial lipid production dropped by 90%; the lipids produced by the residual fraction of the metabolically active bacterial community predominantly carried a heterotrophic signal. Collectively our results strongly suggest that the studied ANME-1 archaea oxidize methane but assimilate inorganic carbon and should thus be classified as methane-oxidizing chemoorganoautotrophs.
authors.affiliation: Organic Geochemistry Group, MARUM-Center for Marine Environmental Sciences and Department of Geosciences, University of Bremen, D-28359 Bremen, Germany. kellermann.matthias@gmail.com
authors.forename: Matthias Y
authors.initials: MY
authors.lastname: Kellermann
authors.forename: Gunter
authors.initials: G
authors.lastname: Wegener
authors.forename: Marcus
authors.initials: M
authors.lastname: Elvert
authors.forename: Marcos Yukio
authors.initials: MY
authors.lastname: Yoshinaga
authors.forename: Yu-Shih
authors.initials: YS
authors.lastname: Lin
authors.forename: Thomas
authors.initials: T
authors.lastname: Holler
authors.forename: Xavier Prieto
authors.initials: XP
authors.lastname: Mollar
authors.forename: Katrin
authors.initials: K
authors.lastname: Knittel
authors.forename: Kai-Uwe
authors.initials: KU
authors.lastname: Hinrichs
mesh_terms: D000693:Anaerobiosis; D052818:Autotrophic Processes / Q000502:physiology*; D001419:Bacteria / Q000378:metabolism*; D058448:Biota; D002244:Carbon / Q000378:metabolism; D057486:Carbon Cycle / Q000502:physiology*; D002247:Carbon Isotopes; D007553:Isotope Labeling; D050356:Lipid Metabolism; D008697:Methane / Q000378:metabolism*; D008800:Mexico; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction
chemical_list: D002247:Carbon Isotopes; D002244:Carbon; D008697:Methane