PURIFICATION OF THE BACTERIOCIN BAVARICIN MN AND CHARACTERIZATION OF ITS MODE OF ACTION AGAINST LISTERIA-MONOCYTOGENES SCOTT A-CELL AND LIPID VESICLES

Bavaricin MN was purified from Lactobacillus sake culture supernatant 135-fold with a final yield of 11%, Sequence analysis revealed bavaric in MN to be a 42-amino-acid peptide having a molecular weight of 4,769 and a calculated pI of 10.0. Computer analysis indicated that the C-t erminal region may form an a-helical structure with an amphipathic nat ure deemed important in the interaction of bacteriocins with biologica l membranes, Bavaricin MN rapidly depleted the membrane potential (Del ta p) of energized Listeria monocytogenes cells in a concentration-dep endent fashion. At a bavaricin MN concentration of 9.0 mu g/ml, the De lta p decreased by 85%. Both the electrical potential (Delta Psi) and Z Delta pH components of the Delta p were depleted, and this depletion was not dependent on a threshold level of proton motive force. In add ition to studying the effect of bavaricin MN on the Delta p of vegetat ive cells, bavaricin MN-induced carboxyfluorescein (CF) efflux from L. monocytogenes-derived lipid vesicles was also characterized, Bavarici n MN-induced CF leakage was also concentration dependent with an optim um of pH 6.0. The rate of CF efflux was 63% greater in lipid vesicles in which a Delta Psi was generated compared with that in lipid vesicle s in the absence of a Delta Psi.