Mode of Action of Nisin Z against Listeria monocytogenes Scott A Grown at High and Low Temperatures

Abstract

Nisin Z, a natural nisin variant, was recently isolated from Lactococcus lactis subspecies lactis NIZO 22186. The gene for this lantibiotic, designated nisZ , has been cloned, and its nucleotide sequence was found to be identical to that of the precursor nisin gene with the exception of a single mutation resulting in the substitution of Asn-27 for His-27 in the mature polypeptide (J. W. M. Mulders, I. J. Boerrigter, H. S. Rollema, R. J. Siezen, and W. M. de Vos, Eur. J. Biochem. 201:581-584, 1991). A K + electrode was used to investigate the effect of various 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 respiratory 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 (Gd 3+ ) was an efficient inhibitor and prevented nisin Z activity completely at a concentration of 0.2 mM. Nisin Z-induced loss of cell K + was reduced at low temperatures, presumably as a result of the increased ordering of the lipid hydrocarbon chains in the cytoplasmic membrane. In cells grown at 30°C, the action of nisin Z was prevented below 7°C, whereas in cells grown at 4°C nisin Z was able to induce K + leakage at this low temperature.