Effect of beta-lactam antibiotics on in vitro peptidoglycan cross-linking by a particulate fraction from Escherichia coli K-12 and Bacillus megaterium KM.

The binding constants of several beta-lactam antibiotics towards penicillin-binding components in Escherichia coli K-12 (Spratt, Eur. J. Biochem. 72:341-352, 1977) and the antibiotic concentrations required to inhibit the peptidoglycan transpeptidase of E. coli 50% were compared. Penicillin-binding component 1B may have been the transpeptidase working in vitro. The structure-activity relationships of beta-lactam antibiotics and the mechanisms of action in E. coli and Bacillus megaterium are discussed.