The role of Rnf in ion gradient formation inDesulfovibrio alaskensis

Abstract

Rnf is a membrane protein complex that has been shown to be important in energy conservation. Here,Desulfovibrio alaskensisG20 and Rnf mutants of G20 were grown with different electron donor and acceptor combinations to determine the importance of Rnf in energy conservation and the type of ion gradient generated. The addition of the protonophore TCS strongly inhibited lactate-sulfate dependent growth whereas the sodium ionophore ETH2120 had no effect, indicating a role for the proton gradient during growth. Mutants inrnfAandrnfDwere more sensitive to the protonophore at 5 µM than the parental strain, suggesting the importance of Rnf in the generation of a proton gradient. The electrical potential (ΔΨ), ΔpH and proton motive force were lower in thernfAmutant than in the parental strain ofD.alaskensisG20. These results provide evidence that the Rnf complex inD. alaskensisfunctions as a primary proton pump whose activity is important for growth.