Washed normal staphyloccal cells, respiring in solutions containing glucose and various mixtures of amino acids, utilized the amino acids with an increase in the cellular protein nitrogen.

Similar cells under the same conditions, but exposed to penicillin G, utilized oxygen, phosphate, and amino acids at essentially the same rates, but there was no increase in the protein nitrogen of the cells.

Penicillin-treated washed cells, when utilizing amino acids, produced increased amounts of extracellular substances containing non-amino nitrogen in quantities approximately equivalent to the amino acid nitrogen utilized. The non-amino fraction could be tentatively identified as polypeptide, which was produced, instead of cellular protein, when penicillin was present.