PENICILLIN UPTAKE BY BACTERIAL CELLS

Abstract

Saccharomvces cerevisiae cells equilibrated with equal volumes of penicillin G solutions of varying concns. do not adsorb penicillin, nor does penicillin penetrate the cell wall. When Staphylococcus aureus cells are similarly equilibrated, 2 types of uptake occur: a specific uptake of approx. 0.8 u./ml. that is independent of the extracellular penicillin concn., and a diffusion of penicillin into the cell so that the intracellular water has the same penicillin concn. as the extracellular water. Uptake is independent of the time of equilibration. Radioactive penicillin of high specific activity was employed to demonstrate the firmness with which the penicillin specifically absorbed is bound. Neither extensive washing nor equilibration with solns. of nonradioactive penicillin containing 10,000 u./ml. released bound radioactive penicillin from the bacterial cells. Calculations showed that approx. 750 molecules of penicillin per bacterial cell were specifically absorbed.