Putative model of energy-conserving electron transfer reactions in Mt. thermophila. A1AO, A1AO ATP synthase; CM, cytoplasmic membrane; Ech, Ech hydrogenase; Fdred, reduced ferredoxin; Fdox, oxidized ferredoxin; FpoABCDHIJKLMN, subunits A to N of the F420H2 dehydrogenase; FpoF, F subunit of the F420H2 dehydrogenase; H4MPT, tetrahydromethanopterin; HdrDE, heterodisulfide reductase subunits D and E; Mtr, methyltransferase; MP, methanophenazine; MPH2, reduced methanophenazine; Rnf, Rnf complex; Vho/t, viologen-reducing hydrogenase one/two; (+), present in Mt. thermophila; (−), not present in Mt. thermophila.