Sensitive Thiazoleless Mutant of Salmonella typhimurium

ses. Enzymatic determinations demonstrated, however, that the enzymes of the glycolytic pathway (up to the formation of triose phosphates) were present and active at 25 and 37 C. At 42 C, the mutant did not grow with any of the carbon sources used. At both 37 and 42 C, the mutant grew perfectly well with hexoses if yeast extract was present. The metabolite required for growth was thiamine or, specifically, its thiazole moiety. If glucose was added to a culture growing in glycerol, at 37 C, growth was inhibited. This inhibition was relieved by the addition of thiamine or thiazole. Thus, at 37 C and only in the presence of hexoses, the mutant manifests a requirement for thiazole. This auxotrophy is absolute at 42 C. These data indicate that, in this mutant, some derivative of hexoses inhibits the synthesis of thiazole, and that this inhibition is also dependent on the temperature of incubation. The position in the bacterial chromosome of the genetic locus of this lesion (thz-) was determined by conjugation and found to coincide with the only thiamine (thi) locus so far reported.