The similarity in action of bacitracin and penicillin on the staphylococcus.

Gale and his group have shown that (1) staphylococci grown "deficient" in glutamic acid can concentrate the free amino acid inside the cells, provided a source of eneigy is present (Gale, 1947; Taylor, 1947); (2) penicillin, in growthinhibitory amounts, prevents the uptake of glutamic acid by staphylococci if the organisms are first grown for a short period in the presence of the antibiotic (Gale and Taylor, 1947); and (3) penicillin-resistant staphylococci do not concentrate glutamic acid wN-ithin the cells and no longer require the presence of preformed amino acids and nicotinamide for growrth (Gale and Rlodwell, 1948). Subsequently it has become apparent that penicillin-sensitive staphylococci may be "trained" to the penicillin-resistant state either by being subcultured in increasing concentrations of penicillin or by being "trained" to grow in the absence of certain nutrients, particularly amino acids (Gale and Rodwell, 1949). In either case organisms are obtained that have increased synthetic abilities and that are resistant to the action of penicillin. The effects of bacitracin2 on the process of glutamic acid uptake and on the gIrowtth of certain strains of staphylococci are described in this note. The methods used were similar to those previously employed by Gale (1945). A penicillin-sensitive strain of Staphylococcus aureus ("Duncan") was used in the glutamic acid uptake studies. It wzas partially inhibited in growth by 50 mg per ml of bacitracin and completely inhibited in growth by 100 ,g per ml. The effects of bacitracin on glutamic acid uptake are presented in table 1. In the concentrations used, bacitracin had no effect on the uptake of glutamic acid by resting suspensions of deficient staphylococci but did have a marked inhibitory effect on this process when the cells were first grow-n in its presence for a short period. Further, cells growvn in the presence of the antibiotic showed no impairment in theii fermentative or respiratory activities with glucose as substrate. In these respects, bacitracin has an action similar to that previously described for penicillin. * The effects of bacitracin and penicillin on the growth of three strains of penicillin-sensitive staphylococci and the penicillin-resistant variants derived from two of them are presented in table 2. The penicillin-sensitive strains are noted to be inhibited in growvth by low concentrations of bacitracin, and the variants made resistant to penicillin are seen to be resistant also to bacitracin.