Ributes to ATP synthesis. An electron transport chain has been proposed for Methanosarcina acetivorans, the only non-H2-metabolizing Methanosarcina species for which the genome has been sequenced. The genome doesn’t encode Ech hydrogenase (ten), further excluding H2 in electron transport. In contrast to M. barkeri and M. mazei, M. acetivorans synthesizes a six-subunit complex (Rnf) with higher identity to membrane-bound Rnf (Rhodobacter nitrogen fixation) complexes from the domain Bacteria (11). The genes (MA0657MA0664), encoding the Rnf complicated of M. acetivorans, are cotranscribed using a gene (MA0658) that encodes a heme cytochrome c and yet another gene (MA0665) that encodes a hypothetical membrane integral protein with unknown function (11). The cytochrome c is synthesized at high levels in acetate-grown cells, exactly where it dominates the UV-visible spectrum of purified membranes (11). Reduction of purified membranes from acetategrown cells with Fd results in reduction from the cytochrome c, that is reoxidized by the addition of either CoM-S-S-CoB or an analog of MP, 2-hydoxyphenazine (12). Decreased 2-hydoxyphenazine is reoxidized by membranes, and this is dependent on the additionReceived 16 May 2013 Accepted 28 June 2013 Published ahead of print eight July 2013 Address correspondence to James G. Ferry, [email protected]. * Present address: Ricardo Jasso-Ch ez, Departamento de Bioquimica, Instituto Nacional de Cardiologia, Tlalpan, Mexico. Copyright 2013, American Society for Microbiology. All Rights Reserved. doi:10.1128/JB.00581-September 2013 Volume 195 NumberJournal of Bacteriologyp. 3987jb.asm.orgJasso-Ch ez et al.of CoM-S-S-CoB, which implies the translocation of protons. Additionally, it has been reported that a (MA0658-MA0665) mutant of M. acetivorans fails to develop with acetate as the sole substrate (13). The combined evidence supports a H2-independent membrane-bound electron transport chain originating with Fd and culminating with reduction of CoM-S-S-CoB that entails the Rnf complicated, cytochrome c, and MP. More recently, it was reported that inverted membrane vesicles of M. acetivorans catalyze Na transport coupled for the oxidation of Fd and reduction of CoM-S-S-CoB (14). It was additional reported that a rnf mutant is unable to develop with acetate and that Na transport coupled to Fd:CoM-S-S-CoB oxidoreductase activity of membranes is abolished (14), which supports a role for the Rnf complicated in generation of a Na gradient supplementing the Na gradient generated by Mtr.Fengycin As a result, it is anticipated that each Na and H gradients are generated in the course of acetate-dependent development of M.DPH acetivorans.PMID:25023702 This conjecture is consistent together with the concurrently coupled translocation of each Na and H by the ATP synthase of M. acetivorans (15, 16); however, the Na /H ratio for optimal ATP synthesis is yet to be investigated. The genome of M. acetivorans encodes a homolog of the multisubunit Na /H antiporter Mrp, which was 1st characterized from species within the domain Bacteria. The homolog is upregulated in M. acetivorans in response to development with acetate (11, 17), a result constant with an Mrp requirement for optimal acetotrophic development. Mrp homologs from species within the domain Bacteria function in Na resistance, pH homeostasis of alkaliphiles, bile salt resistance, and energy-yielding metabolism (182). While Mrp homologs are encoded inside the genomes of species from the domain Archaea (18), none has been investigated. Here, we report the phenotypic traits of a mrpA m.