RESEARCH ARTICLE

Abstract The combined action of nisin and lactacin F, two bacteriocins produced by lactic acid bacteria, is ad-ditive. In this report, the basis of this effect is examined. Channels formed by lactacin F were studied by experi-ments using planar lipid bilayers, and bactericidal effects were analyzed by flow cytometry. Lactacin F produced pores with a conductance of 1 ns in black lipid bilayers in 1 mM KCl at 10 mV at 20 C. Pore formation was strongly dependent on voltage. Although lactacin F formed pores at very low potential (10 mV), the depen-dence was exponential above 40 mV. The injuries induced by nisin and lactacin F in the membranes of Lactobacillus helveticus produced different flow cytometric profiles. Probably, when both bacteriocins are present, each acts separately; their cooperation may be due to an increase in the number of single membrane injuries