HYDROGENASE COUPLED REACTIONS IN CAMPYLOBACTER-RECTUS

In an earlier publication Campylobacter rectus was shown to grow with H-2 as the electron donor and fumarate as the electron acceptor and wh ole cells oxidized H-2 in the presence of fumarate or elemental sulfur . Relatively little is known about the metabolism of Campylobacter rec tus and our studies were to address physiological issues of H-2 metabo lism. We report that in the presence of methyl viologen, the oxidation of H-2 is coupled to the reduction of nitrite but not nitrate. At lea st two hydrogenases are present in C. rectus, one in the periplasmic r egion and another in the plasma membrane. A soluble c-type cytochrome with an adsorption peak at 553 nm was demonstrated in the soluble frac tion while a b-type cytochrome in the membrane has an adsorption peak at 560 nm. The electron flow from hydrogenase to fumarate in reactions containing plasma membranes is inhibited by 2-heptyl-4-hydroxyquinoli ne n-oxide. A model is proposed to summarize the electron transport ac tivities of this bacterium growing under anaerobic conditions. (C) 199 6 Academic Press