Nisin, which is produced by certain Lactococcus lactis strains,
is the most extensively studied bacteriocin produced by a Grampositive
organism (Gross and Morell 1971). Our lab has previously
demonstrated that pediocin or nisin can inhibit L. monocytogenes
growth on cooked chicken (Goff and others 1996; Janes and others
2002). 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 (Abee and others 1994). 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