Anaerobic Growth of Methanosarcina acetivorans C2A on Carbon Monoxide: An Unusual Way of Life for a Methanogenic Archaeon

All methanogenic Archaea examined to date rely on methanogenesis as their sole means of energy conservation. Among these are ones that use carbon monoxide as a growth substrate, producing methane via a pathway that involves hydrogen as an intermediate. To further examine the role of hydrogen in this...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2004-11, Vol.101 (48), p.16929-16934
Main Authors: Rother, Michael, Metcalf, William W., Wolfe, Ralph S.
Format: Article
Language:English
Subjects:
Acetates
Acetic Acid - metabolism
Archaea
Bacteria
Biological Sciences
Carbon monoxide
Carbon Monoxide - metabolism
Cell growth
Electrons
Enzymes
Ferries
Formates
Formates - metabolism
Metabolism
Methane
Methane production
Methanogens
Methanosarcina
Methanosarcina - growth & development
Methanosarcina acetivorans
Microbiology
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Summary:All methanogenic Archaea examined to date rely on methanogenesis as their sole means of energy conservation. Among these are ones that use carbon monoxide as a growth substrate, producing methane via a pathway that involves hydrogen as an intermediate. To further examine the role of hydrogen in this process, we tested the ability of Methanosarcina acetivorans C2A, a metabolically versatile methanogen devoid of significant hydrogen metabolism, to use CO as a growth substrate. M. acetivorans grew on CO to high cell densities (≈ 1× 108per ml) with a doubling time of ≈24 h. Surprisingly, acetate and formate, rather than methane, were the major metabolic end products as shown by13C NMR studies and enzymatic analysis of culture supernatants. Methane formation surpassed acetate/formate formation only when the cultures entered stationary growth phase, strongly suggesting that M. acetivorans conserves energy by means of this acetogenic and formigenic process. Resting cell experiments showed that methane production decreased linearly with increasing CO partial pressures, consistent with inhibition of methanogenesis by CO. Transposon-induced M. acetivorans mutants with lesions in the operon encoding phosphotransacetylase and acetate kinase failed to use either acetate or CO as growth substrates, indicating that these enzymes are required for both aceticlastic methanogenesis and carboxidotrophic acetogenesis. These findings greatly extend our concept of energy conservation and metabolic versatility in the methanogenic Archaea.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0407486101