Generation of a superoxide dismutase (SOD)-deficient mutant of Campylobacter coli: Evidence for the significance of SOD in Campylobacter survival andcolonization

The microaerophilic nature of Campylobacter species implies an inherent sen sitivity towards oxygen and its reduction products, particularly the supero xide anion. The deleterious effects: of exposure to superoxide radicals are counteracted by the activity of superoxide dismutase (SOD). We have shown previously that Campylobacter coli possesses: an iron cofactored SOD. The s odB gene of C. coli UA585 was insertionally inactivated by the site-specifi c insertion of a tetO cassette. Organisms harboring the inactivated gene fa iled to produce a biologically functional form of the enzyme. While the abi lity of this mutant to grow in aerobic conditions was unchanged relative to the parental strain, its survival was severely compromised when nongrowing cells were exposed to air Accordingly; the SOD-deficient mutant was unable to survive for prolonged periods in model foods. Furthermore, inactivation of the sodB gene decreased the colonization potential in an experimental i nfection of 1-day-old chicks. In contrast, strain CK100, which is deficient in catalase activity, showed the same survival and colonization characteri stics as the parental strain. These results indicate that SOD, but not cata lase, is an important determinant in the ability of C. call to survive aero bically and for optimal colonization within the chicken gut.