INFLUENCE OF GENES ENCODING PROTON-TRANSLOCATING ENZYMES ON SUPPRESSION OF SALMONELLA-TYPHIMURIUM AND COLONIZATION

Twenty-four-hour-old, aerobically grown, Luria-Bertani broth cultures of Salmonella typhimurium F98 suppressed the growth of a spectinomycin -resistant (Spc(r)) derivative of the same strain inoculated at 10(3) CFU ml(-1). This growth suppression is genus specific and RpoS indepen dent, and it is not solely a result of nutrient depletion (P. A. Barro w, M. A. Lovell, and L. Zhang-Barber, J. Bacteriol. 178:3072-3076, 199 6). Mutations in three genes are shown here to significantly reduce gr owth suppression under these conditions. The mutations were located in the nuo, cyd, and unc operons, which code for the NADH dehydrogenase I, cytochrome d oxidase, and F0F1 proton-translocating ATPase complexe s, respectively. When cultures were grown under strictly anaerobic con ditions, only the unc mutant did not suppress growth. Prior colonizati on of the alimentary tract of newly hatched chickens with the S. typhi murium F98 wild type or nuo or cyd mutants suppressed colonization by an S. typhimurium F98 Spc(r) derivative inoculated 23 h later. In cont rast, the S. typhimurium anc mutant did not suppress colonization. The nuo and unc mutants showed poorer growth on certain carbon sources. T he data support the hypothesis that growth suppression operates becaus e of the absence of a utilizable carbon source or electron acceptor.