Abstract

Most methanogenic archaea can reduce CO₂ with H₂ to methane, and it is generally assumed that the reactions and mechanisms of energy conservation that are involved are largely the same in all methanogens. However, this does not take into account the fact that methanogens with cytochromes have considerably higher growth yields and threshold concentrations for H₂ than methanogens without cytochromes. These and other differences can be explained by the proposal outlined in this Review that in methanogens with cytochromes, the first and last steps in methanogenesis from CO₂ are coupled chemiosmotically, whereas in methanogens without cytochromes, these steps are energetically coupled by a cytoplasmic enzyme complex that mediates flavin-based electron bifurcation.

Author affiliations

1. Max Planck Institute for Terrestrial Microbiology, Karl-von-Frisch-Strasse, D-35043 Marburg, Germany.
2. Laboratory for Microbiology, Faculty of Biology, Philipps University Marburg, D-35032 Marburg, Germany.

Correspondence to: Rudolf K. Thauer¹ Email: thauer@mpi-marburg.mpg.de

Published online 30 June 2008

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