Biochemical studies of melibiose metabolism in wild type and mel mutant strains of Salmonella typhimurium.

I identified two enzyme activities, alpha-galactosidase and a galactoside permease, required for melibiose metabolism by Salmonella typhimurium. These activities are very low under normal growth conditions, but their production can be induced by melibiose and gratuitously by melibiitol. Melibiose induction is severely inhibited by glucose, but the glucose effect can be countered by 3', 5' cyclic adenosine monophosphate. I isolated two phenotypic classes of mutants not able to utilize melibiose as a carbon source. One class, Car(-), is deficient in the phosphotransferase system. The other, Mel, lacks either alpha-galactosidase, galactoside permease, or both functions.