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Effect of Benzylpenicillin on the Synthesis and Structure of the Cell Envelope of Neisseria gonorrhoeae

The effect of benzylpenicillin on the synthesis and morphology of the cell envelope ofNeisseria gonorrhoeae was examined. Penicillin immediately stopped murein synthesis; it also enhanced the rate of turnover of glucosamine, but not diaminopimelic acid, in the murein. In addition, penicillin greatly increased the shedding of lipid and lipopolysaccharide into the medium. In the electron microscope, protrusions of the cell membrane were evident, as well as apparent holes in the murein cell wall. All of these changes occurred while active synthesis was taking place, before the lysis of the cells. Lysis could be prevented by growing the cells at low pH and high concentrations of Mg2e; however, the effects of penicillin on murein synthesis and turnover and on the release of lipid were not affected. Penicillins interfere with murein (peptidogly-can) synthesis in bacteria by inhibiting the final step of murein synthesis, the formation of cross- bridges between the peptide side chains of newly formed peptidoglycan strands and the peptide chains of the completed cell wall (2, 8). The secondary effects of this inhibition are manifold. Several the uncross-linked peptidoglycan strands the growth medium Vol. 13, no. 3, p. 514, paragraph 1: A section of the Introduction was inadvertently left out. This section (line 32) should read as follows: ... less active (7, 19). Bacterial mutants with defective murein hydrolases also do not undergo lysis during penicillin treatment (34, 37). It was recently demonstrated for Neisseria gonorrhoeae (4, 5, 10) that low pH and high concentrations of Mg2" give some protection against penicillin-induced lysis. In this communication, we have compared the morphological and biochemical effects of benzylpenicillin on the envelope of this gram-negative bacterium under lysis-protective and under lysis-permissive conditions.