Matthias Y. Kellermann Gunter Wegener Marcus Elvert Marcos Yukio Yoshinaga Yu-Shih Lin Thomas Holler Xavier Prieto Mollar Katrin Knittel and Kai-Uwe Hinrichs. Autotrophy as a predominant mode of carbon fixation in anaerobic methane-oxidizing microbial communities.
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 13C 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 13C-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.
