Penicillin Induced Lysis in Escherichia coli

Abstract

The paper is a survey of the action of [alpha]-aminobenzylpenicillin (ampicillin) on Escherichia coli. The rate at which lysis was induced in exponentially growing organisms was studied for different concentrations of ampicillin, using pure D- and L-forms as well as a 6:4 mixture. The interpolated concentration of penicillin which gives lysis in one generation (the "LIOG value") has been used for characterization of penicillin derivatives with twelve different side chains. These LIOG values were also used for characterization of some penicillin-resistant mutants. The lysis rate has been recorded for cultures of concentrations between 4 x 105 and 108 rods/ml and found to be independent of the population density. The use of five different media showed that for a given ampicillin concentration the time of lysis was proportional to the growth rate. The addition of penicillinase to a culture growing with penicillin rescued the organisms as late as a few minutes before lysis. Synergistic effects on the lysis rates were found with 6-amino-penicillanic-acid and two amino-acids, which as residues are side chains, in two of the penicillins tested. Different models for penicillin action in E. coli are discussed.