PROTAMINE-INDUCED PERMEABILIZATION OF CELL ENVELOPES OF GRAM-POSITIVEAND GRAM-NEGATIVE BACTERIA

The inhibitory effect of the cationic peptide protamine on Listeria mo nocytogenes, Escherichia coli, and Shewanella putrefaciens has been st udied in detail, The addition of protamine (10 to 1,000 mu g/ml) resul ted in inhibition of oxygen consumption after less than 1 min and loss of intracellular carboxyfluorescein and ATP after 2 to 5 min. Maximum antibacterial activity was reached at alkaline pH and in the absence of divalent cations. The efficient permeabilization of cell envelopes of both gram-positive and gram-negative bacteria suggests that protami ne causes a general disruption of the cell envelope, leading to a rapi d and nonspecific efflux of low- and high-molecular-weight compounds.