Has Rnf Complex A Pivotal Role In Anaerobic Growth Of Other Microorganisms?

DEMERGASSO CS; ACOSTA-GRINOK M; VAZQUEZ SC; GILIANI N

Congreso; World Microbe Forum 2021; 2021

ASM-FEMS

The Rnf complex plays a pivotal role as a bioenergetic enzyme, it acts as an ion-motive electron transport chain that catalyzes the reversible oxidation of reduced ferredoxin with NAD+, coupling this exergonic reaction with the build-up of an electrochemical proton or sodium ion potential. It has been demonstrated that the Rnf complex is associated with the generation of either a Na+ or an H+ gradient. The Rnf is one of the two components of the energy conservation mechanism, flavin-based electron bifurcation, together with the electron-bifurcating enzyme. The role of Rnf has been confirmed in acetogens, acetoclastic methanogens, sulfate reducers, and other strict anaerobes lacking cytochromes, quinones, or other membrane-soluble electron carriers, such as Acetobacterium woodii, Escherichia coli, Clostridium tetani, Methanosarcina acetivorans, and Desulfovibrio aleskensis, predominantly among members of Firmicutes. The occurrence of Rnf was observed by means of the genomic analysis of some arsenic-reducing microorganisms. In addition, the reported reduction potential of the molybdoenzyme arsenite oxidase had indicated the potential of transition metal ions to be the site of electron bifurcation, and the molybdenum in the arsenite oxidases could be one example. It is known the bidirectional function of this kind of arsenite oxidases.The genome analysis of an arsenate reducing Firmicutes, revealed the presence of genes for the proteins RnfC, D, G, E, A, and B and the cytoplasmic arsenate reductase gene, arsC, but it lacks a homolog for the respiratory arsenate reductase gene, arrAB. Those features, together with the absence of membrane-soluble electron carriers and membrane-soluble arsenic reducing enzymes allow us to hypothesized that Rnf could have a role in energy conservation from arsenic reduction. We arrived at this hypothesis on the basis of the culture behavior and the genome analysis of the isolated strain Fusibacter ascotence 3D3, obtained from Salar de Ascotán, Chile.