Antibacterial and antimembrane activities of cecropin A in Escherichia coli

The ability of cecropin A to permeabilize and depolarize the membranes of E scherichia coli ML-35p bacteria has been compared to its bactericidal activ ity in an extension of earlier studies performed on synthetic lipid vesicle membranes (L. Silvestro, K, Gupta, J, H, Weiser, and P, Il, Axelsen, Bioch emistry 36:11452-11460, 1997), Our results indicate that differences in the concentration dependences of membrane permeabilization and depolarization seen in synthetic vesicles are not manifested in whole bacteria, The concen tration dependences of both phenomena roughly correlate with bactericidal a ctivity, suggesting that the bactericidal mechanism of cecropin A is relate d to membrane permeabilization.