Action of Penicillin on Bacterial Utilization of Amino Acids and Peptides

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Abstract
A bacterial strain (SF), which grows in a simple synthetic medium, and which shows a preference for L-leucylglycine rather than for L-leucine or glycine in mixture, was inoculated into media containing either L-leucylglycine or a mixture of L-leucine and glycine, together with increasing quantities of penicillin G sodium salt. 500U./ml. inhibited bacterial growth only slightly in presence of the peptide, but smaller quantities inhibited in the mixture of the component amino acids, due chiefly to its interference with the utilization of glycine. The assimilation of glycine by strain SF involves its prior incorporation into a peptide, and the bacteriostatic action of penicillin is due to an inhibition of peptide synthesis.