Respiratory systems and cytochromes in Campylobacter fetus subsp. intestinalis

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Abstract
Cell suspensions of C. fetus ssp. intestinalis grown microaerophilically in complex media consumed O2 in the presence of formate, succinate and DL-lactate, and membranes had the corresponding dehydrogenase activities. The cells and membranes 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 CO-binding spectrum. Of the total membrane cytochrome c, measured with dithionite as the reductant, 60% 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; formate reduced > 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. Evidently the respiratory chain includes low- and high-potential forms of cytochromes c and b; the CO-binding form of cytochrome c may function as a terminal oxidase.