Respiratory systems and cytochromes in Campylobacter fetus subsp. intestinalis

Cell suspensions of Campylobacter fetus subsp. intestinalis grown microaerophilically in complex media consumed oxygen in the presence of formate, succinate, and DL-lactate, and membranes had the corresponding dehydrogenase activities. The cells and membranes also had ascorbate-N,N,N',N'-tetramethyl-p-phenylenediamine oxidase activity which was cyanide sensitive. The fumarate reductase activity in the membranes was inhibited by p-chloromercuriphenylsulfonate, and this enzyme was probably responsible for the succinate dehydrogenase activity. Cytochrome c was predominant in the membranes, and a major proportion of this pigment exhibited a carbon monoxide-binding spectrum. Approximately 60% of the total membrane cytochrome c, measured with dithionite as the reductant, was also reduced by ascorbate-N,N,N',N'-tetramethyl-p-phenylenediamine. A similar proportion of the membrane cytochrome c was reduced by succinate under anaerobic conditions, whereas formate reduced more than 90% of the total cytochrome under these conditions. 2-Heptyl-4-hydroxyquinoline-N-oxide inhibited reduction of cytochrome c with succinate, and the reduced spectrum of cytochrome b became evident. The inhibitor delayed reduction of cytochrome c with formate, but the final level of reduction was unaffected. We conclude that the respiratory chain includes low- and high-potential forms of cytochromes c and b; the carbon monoxide-binding form of cytochrome c might function as a terminal oxidase.