Methanogenic archaea with and without cytochromes have been identified. This Review focuses on differences in energy conservation during the reduction of CO2 with H2 to CH4. In methanogens with cytochromes, the first and last steps are coupled chemiosmotically, and the authors propose that in methanogens without cytochromes, these steps are coupled by a cytoplasmic enzyme complex that mediates flavin-based electron bifurcation.
- Rudolf K. Thauer
- Anne-Kristin Kaster
- Reiner Hedderich
