GENETIC STUDIES OF CHLORATE-RESISTANT MUTANTS IN SALMONELLA TYPHIMURIUM

Chlorate-resistant mutants (chl-) were isolated from Salmonella typhimurium on the nutrient medium containing glucose and KClO3 by the incubation under anaerobic condition. Phenotypic characterization and linkage analyses by transduction with phage P22 and mating with an Hfr strain, SW1391, demonstrated that the chl mutants can be classified at least into three groups and the corresponding genetic loci are mapped in the order trp-chlC-chlB-chlA-bio-gal, in which only chlA is cotransducible with bio and gal. The chlC mutants showed no growth on a minimal medium, which was weakly restored by the addition of NAD (nicotinamide-adenine dinucleotide) or a commercial vitamin complex. Other pleiotropic mutants requiring lysine and methionine or NAD and those requiring cystein and methionine or NAD for growth on the minimal medium were isolated. Nitrate reductase activity was higher and more stable in the insoluble extract than the soluble one, indicating that this enzyme is membrane-bound.