Penicillin Induced Lysis in Escherichia coli

Abstract

SUMMARYThe paper is a survey of the action of a-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 lo8 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 to 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-aminopenicillanic 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.

Effects of Certain Penicillins on Growth and Cell Division in a Species of Erwinia

“…Tests showed that the effects of benzylpenicillin were independent of inoculum size over a 2.5-foId range. Boman & Eriksson, 1963) we observed that the aminobenzylpenicillins were more toxic than benzylpenicillin. The difference between DL-a-aminobenzylpenicillin ( D : L = 6 : 4) and the pure D-isomer were not such as to indicate a 3-fold higher activity of the pure D-compound, as reported by…”

“…Since the side chain is not essential for the basic activity of penicillin, its influence on activity as observed by Boman & Eriksson (1963) may be a reflexion of its influence on the rate of binding at the active site and on the strength of the bond formed. After binding, the activities of different penicillins are similar.…”

“…after preparation. Sjoberg & Ekstrom (see Boman & Eriksson, 1963) found that the halflife of D-ampicillin at pH ?' and 3 7 ' was about 100 hr; that of L-ampicillin 15 hr.…”

“…D-Ampicillin was about three times as active as L-ampicillin. Boman & Eriksson (1963) found that, in general, aminoalkyl and aminobenzylpenicillins were very active. One exception noted by Cooper (1956) to the generalization that the side chain was not important for activity toward Gram-positive bacteria was the activity of cephalosporin N, a penicillin which contains a-aminoadipic acid as the side chain (Abraham et al 1953).…”

“…One exception noted by Cooper (1956) to the generalization that the side chain was not important for activity toward Gram-positive bacteria was the activity of cephalosporin N, a penicillin which contains a-aminoadipic acid as the side chain (Abraham et al 1953). Boman & Eriksson (1963) also reported that bulky ' non-biological' side chains greatly decreased the antibiotic activity ; two such derivatives, methicillin and 3-p-chlorophenyl-4-(1 ,2,5-oxodiazole)-penicillin, were less active than 6-aminopenicillanic acid. The latter compound, lacking a side chain, was one-tenth as potent as benzylpenicillin.…”