Abstract
1) DL-Norleucine, L-histidine, L-phenylalanine or human red cell inhibits the growth of an assay organism, E. coli #215,while these inhibitions are relieved by the addition to the medium of methionine-free casamino acids to yields 0.25 per cent of a final concentration. Casamino acids enables the medium to protect against the growth inhibitory effect which occur during the autoclaving of the medium.2) Among 29 microorganisms tested, the greatest amount of vitamin B_<12> was found in cells of a strain of Pseudomonas aerginosa.
