Nutritional Studies of Cysteineless Mutants of Salmonella typhimurium

SUMMARY: Forty-three separately isolated cyst(e)ineless mutants of Salmonella typhimurium were investigated biochemically. Six main phenotypes were identified, accommodating thirty-nine of the mutants; the remaining four mutants were of intermediate phenotype. The phenotypes are suggested to result from a series of five metabolic blocks in a pathway of cyst(e)ine synthesis in which sulphate can be reduced by two alternative routes, in both of which most of the intermediates are inorganic.