MODE OF ACTION OF NISIN-Z AGAINST LISTERIA-MONOCYTOGENES SCOTT-A GROWN AT HIGH AND LOW-TEMPERATURES

Nisin Z, a natural nisin variant, was recently isolated from Lactococc us lactis subspecies lactis NIZO 22186. The gene for this lantibiotic, designated nisZ, has been cloned, and its nucleotide sequence was fou nd to be identical to that of the precursor nisin gene,vith the except ion of a single mutation resulting in the substitution of Asn-27 for H is-27 in the mature polypeptide (J. W. M. Mulders, I. J. Boerrigter, H . S. Rollema, R. J. Siezen, and W. M. de Vos, fur. J. Biochem. 201:581 -584, 1991). A K+ electrode was used to investigate the effect of vari ous environmental parameters on the action of nisin Z against Listeria monocytogenes. Addition of nisin Z resulted in immediate loss of cell K+, depolarization of the cytoplasmic membrane, inhibition of respira tory activity, and hydrolysis and partial efflux of cellular ATP. The action of nisin Z was optimal at pH 6.0 and was significantly reduced by di- and trivalent cations. The lanthanide gadolinium (Gd3+) was an efficient inhibitor and prevented nisin Z activity completely at a con centration of 0.2 mM. Nisin Z-induced loss of cell K+ was reduced at l ow temperatures, presumably as a result of the increased ordering of t he lipid hydrocarbon chains in the cytoplasmic membrane. In cells grow n at 30 degrees C, the action of nisin Z was prevented below 7 degrees C, whereas in cells grown at 4 degrees C nisin Z was able to induce K + leakage at this low temperature.