Proteomic analysis of the hydrogen and carbon monoxide metabolism of methanothermobacter marburgensis

<p>Hydrogenotrophic methanogenic archaea are efficient H2 utilizers, but only a few are known to be able to utilize CO. Methanothermobacter thermoautotrophicus is one of the hydrogenotrophic methanogens able to grow on CO, albeit about 100 times slower than on H2 + CO2. In this study, we show that the hydrogenotrophic methanogen Methanothermobacter marburgensis, is able to perform methanogenic growth on H₂/CO₂/CO and on CO as a sole substrate. To gain further insight in its carboxydotrophic metabolism, the proteome of M. marburgensis, grown on H₂/CO₂ and H₂/CO₂/CO, was analyzed. Cultures grown with H₂/CO₂/CO showed relative higher abundance of enzymes involved in the reductive acetyl-CoA pathway and proteins involved in redox metabolism. The data suggest that the strong reducing capacity of CO negatively affects hydrogenotrophic methanogenesis, making growth on CO as a sole substrate difficult for this type of methanogens. M. marburgensis appears to partly deal with this by up-regulating co-factor regenerating reactions and activating additional pathways allowing for formation of other products, like acetate.