STUDY OF GROWTH REQUIREMENTS OTHER THAN CYSTEINE OF NATURALLY-OCCURRING ESCHERICHIA-COLI AND KLEBSIELLA SPP AUXOTROPHIC FOR CYSTEINE

Cysteine remains the preferred supplement for cultivation of Cys- auxo trophs in vitro. Methionine, which reduced cysteine requirements, and branched-chain amino acids, which decreased cysteine toxicity, were id entified as the components of casein hydrolysate responsible for growt h enhancement by this additive. Glutathione and DL-homocysteine can be substituted for cysteine. Accumulation of these compounds in patients with renal impairment may favor selection of Cys- strains in vivo.