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SUMMARY: The effect on glutamic acid assimilation of the addition of penicillin to growing cultures of Staphylococcus aureus is described. When Staph. aureus is grown in media containing glutamic acid this substance accumulates in steadily increasing concentration in the cells. The addition of penicillin to the medium is followed after an interval by rapidly decreasing concentration of glutamic acid within the cells.
The assimilation of glutamic acid by normal washed cells is not affected by penicillin in high concentration. The assimilation of glutamic acid by cells which have grown in the presence of penicillin is impaired and may be completely inhibited. Complete inhibition of assimilation is brought about by bactericidal concentrations of penicillin, low concentrations requiring a longer time to become completely effective than high ones. The loss of assimilatory power can be correlated with loss of viability.
Comparison of the general properties of normal and penicillin-inactivated cells show that the respiration, glucose oxidation, glucose fermentation and lysine assimilation of the latter are normal. The internal metabolism of glutamic acid is normal in penicillin-treated cells, but, since the passage of glutamic acid across the cell wall is blocked, is limited by the existing internal concentration.