Methanogenesis pathway.

The predicted pathway of methane formation in M1 based on the scheme of Thauer et al. [15] for methanogens without cytochromes is shown. The diagram is divided into three parts to show the capture of reductant, the reduction of CO₂, and conservation of energy at the methyltransfer step. The main reactions are indicated by thick arrows and enzymes catalysing each step are coloured green. Protein subunits coloured red signify the corresponding genes that were up-regulated during co-culture with Butyrivibrio proteoclasticus. Cofactor participation is indicated with thin arrows. For simplicity, protons are not shown and the overall reaction is not balanced. Membrane-located proteins are contained in light brown boxes and potential vaccine and chemogenomic targets are labelled with a circled V or C, respectively. Full gene names and corresponding locus tag numbers can be found in Table S1. H₄MPT; tetrahydromethanopterin; MF, methanofuran; F₄₂₀, coenzyme F₄₂₀ oxidised; F₄₂₀H₂, coenzyme F₄₂₀ reduced; Fd_ox?, unknown oxidised ferredoxin; Fd_red?, unknown reduced ferredoxin; HSCoM, reduced coenzyme M; HSCoB, reduced coenzyme B, CoMS-SCoB, coenzyme B-coenzyme M heterodisulphide; NADP⁺, nicotinamide adenosine dinucleotide phosphate non-reduced; NADPH, nicotinamide adenosine dinucleotide phosphate reduced.