Involvement of cytochrome bc1 complex in the electron transfer pathway for N2O reduction in a photodenitrifier, Rhodobacter sphaeroides f. s. denitrificans

AbstractThe electron transfer pathway for N2O reduction in Rhodobacter sphaeroides f. s. denitrificans was studied. Myxothiazol and antimycin showed inhibiting effects on the consumption of N2O in whole cells grown under photo-denitrifying conditions. This indicated the involvement of the cytochrome bc1 complex in the process. Reduced redox dyes that donate electrons directly to cytochrome c2 overcame this inhibition. Similar results were obtained with Rhodobacter capsulatus, in contrast to earlier studies by McEwan et al. [(1985) J. Bacteriol. 164, 823–830] that suggested the lack of involvement of the cytochrome bc1 complex in this process. Effects of myxothiazol and antimycin were also observed on the N2O-induced oxidation of cytochromes c1 and c2 and on the simultaneous generation of membrane potential measured by the carotenoid band shift. Thus, reducing equivalents for N2O reduction from substrates pass through the cytochrome bc1 complex coupling to the generation of an electrochemical gradient of protons