Quantitative aspects of penicillin action on Escherichia coli in hypertonic medium.

Duguid (1946) suggested, as a result of observations on bacteria treated with penicillin, that this antibiotic might inhibit the formation of the outer supporting cell wall. Bonifas (1954) observed the formation of globular bodies when cultures of Proteus vulgaris were treated with penicillin, and investigated the effect of hypertonic media, already used to stabilize the lysozyme induced protoplast of Bacillus megaterium by Weibull (1953). Lederberg (1956, 1957) demonstrated the conversion of both Escherichia coli and Salmonella typhi to spherical osmotically fragile bodies by penicillin, provided the medium contained 0.33 M sucrose and preferably 0.2 per cent MgSO4 7H20. Similar results have been reported for P. vulgaris (Liebermaster and Kellenberger, 1956); E. coli (Hahn and Ciak, 1957); Alcaligenes faecalis (Lark, 1958a, b); Cloaca cloacae, Citrobacter freundii, Klebsiella aerogenes, Serratia marcescen3, Proteus morganii, Pseudomonas aeruginosa, Pseudomonas hydrophila, E. coli (two strains), Vibrio cyclosites, and Vibrio neocistes (Hugo, 1958); E. coli strain B (Hurwitz, Reiner, and Landau, 1958); E. coli strain K12 and Proteus mirabilis (Landman, Altenbern, and Ginoza, 1958); and Xanthomonas phaseoli (Nozzolillo and Hochster, 1959). Brenner et al. (1958) suggested the term protoplast should be retained only if complete absence of cell wall is proved and the term round body or spheroplast refers to an observed microscopical appearance without commitment as to presence or absence of certain cell wall components, and the second term will be used hereafter. Quantitative aspects of the changes occurring during penicillin induced spheroplast formation in cultures of a strain of E. coli are reported in this paper.