SERINE UTILIZATION AS A POTENTIAL COMPETITION MECHANISM BETWEEN SALMONELLA AND A CHICKEN CECAL BACTERIUM

Our objective in this study was to use batch culture to estimate growt h kinetic parameters for a growth-limiting amino acid, serine, in Salm onella typhimurium and a in chicken cecal bacterium, Escherichia fergu sonii, and to test these predictions for competitiveness in a mixed cu lture of the two organisms. Under anaerobic growth conditions, the two bacteria grew only when serine was provided as the nitrogen source. W hen serine was used as a carbon source in aerobic media, the maximum g rowth rates of the two organisms were considerably lower and the affin ity constants were higher than when serine was used as a nitrogen sour ce. The maximum growth rates of the two organisms were lower in anaero bic media than in aerobic media, but serine anaerobic affinity constan ts were lower than those from aerobic media. In aerobic mixed culture, S. typhimurium outgrew E. fergusonii in N-limited minimal media conta ining 0.1 mM serine but in N-nonlimited minimal media containing 10 mM serine, E. fergusonii outgrew S. typhimurium. In anaerobic mixed cult ure, E. fergusonii outgrew S. typhimurium in media containing both 0.1 mM and 10 mM serine concentrations. It appears that the cause of inhi bition of Salmonella with serine as the variable nutrient differs depe nding on the oxidation-reduction status.