Nisin, which is produced by certain Lactococcus lactis strains, is the most extensively studied bacteriocin produced by a Grampositive organism. Our lab has previously demonstrated that pediocin or nisin can inhibit L. monocytogenes
growth on cooked chicken . Mode of action is believed to be pore formation initiated by the electrostatic attraction of the cationic nisin to the negatively charged phospholipids of the cell. Nisin inserts into the membrane and orients perpendicularly to the membrane and, since it does not lose contact with the phospholipids in the course of this rearrangement, they bend the bilayer and force a transient pore to open. According to Bruno and others (1992), healthy cells of Listeria have a proton motive force (PMF) of −160 mV, which is typical of facultative anaerobes. Bruno and