Effect of cephapirin on formation of D-alanine carboxypeptidase in growing Bacillus subtilis cells.

Cephapirin was utilized to examine the interaction of beta-lactam antibiotics with growing Bacillus subtilis cells and the biological effects simultaneously produced. Saturation binding and quantitative cell death were observed at the cephapirin concentration of 0.1 mug/ml. Cephapirin bound to all penicillin-binding proteins except the d-alanine carboxypeptidase. A specific [(14)C]benzylpenicillin-binding assay was developed for the d-alanine carboxypeptidase. At the lowest saturating concentration of antibiotic (0.1 mug/ml), cephapirin inhibited formation of the d-alanine carboxypeptidase. Upon incubation with cephapirin, 18% of the membranous d-alanine carboxypeptidase was released into the media. The data suggest that beta-lactam antibiotics may affect the formation of bacterial cytoplasmic membranes in addition to their effect on cell wall synthesis.