Some Characteristics of Nisin Z, a Peptide Antibiotic Produced by Lactococcus lactis IO-1

Lactococcus lactis IO-1 isolated in our laboratory produces a peptide antibiotic, a natural nisin variant, nisin Z. Nisin Z was heat stable at acidic pH and showed a bactericidal mode of action against an indicator strain, Bacillus subtilis C1. The effect of proteolytic enzyme treatment on the activity and the antimicrobial spectrum were tested. These results indicated nearly the same characteristics as those of nisin A. In this study, it was found that two nisin variants (nisin Z and nisin A) were practically inactivated by proteinase K and actinase E. Interestingly, nisin-producing strains, L. lactis IO-1 and L. lactis NCDO 497 (a nisin A producer) were sensitive to a high concentration of nisin variants including their own products. The growth of a Gram-negative bacterium, Escherichia coli, was also inhibited by a high concentration of nisin, although nisin producers and Gram-negative bacteria are generally resistant to nisin variants.