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Methane as Fuel for Anaerobic Microorganisms
Author(s) -
Thauer Rudolf K.,
Shima Seigo
Publication year - 2008
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1196/annals.1419.000
Subject(s) - anaerobic oxidation of methane , methane , methane monooxygenase , methanogenesis , chemistry , oxidative coupling of methane , archaea , sulfate , denitrification , methanotroph , inorganic chemistry , biochemistry , organic chemistry , nitrogen , gene
Methane has long been known to be used as a carbon and energy source by some aerobic alpha‐ and delta‐proteobacteria. In these organisms the metabolism of methane starts with its oxidation with O 2 to methanol, a reaction catalyzed by a monooxygenase and therefore restricted to the aerobic world. Methane has recently been shown to also fuel the growth of anaerobic microorganisms. The oxidation of methane with sulfate and with nitrate have been reported, but the mechanisms of anaerobic methane oxidation still remains elusive. Sulfate‐dependent methane oxidation is catalyzed by methanotrophic archaea, which are related to the Methanosarcinales and which grow in close association with sulfate‐reducing delta‐proteobacteria. There is evidence that anaerobic methane oxidation with sulfate proceeds at least in part via reversed methanogenesis involving the nickel enzyme methyl‐coenzyme M reductase for methane activation, which under standard conditions is an endergonic reaction, and thus inherently slow. Methane oxidation coupled to denitrification is mediated by bacteria belonging to a novel phylum and does not involve methyl‐coenzyme M reductase. The first step in methane oxidation is most likely the exergonic formation of 2‐methylsuccinate from fumarate and methane catalyzed by a glycine‐radical enzyme.