Characterization of Lantibiotic Nisin Z Produced by Lactococcus lactis IO-1

Lactococcus lactis IO-1 isolated in our laboratory produces a peptide antibiotic, a natural nisin variant, nisin Z. Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that molecular weight of nisin Z was almost the same as that of nisin A with 3.4 kDa, while reversed-phase high performance chromatography did apparent differences in elution time. Nisin Z was heat stable at acidic pH and showed 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 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 (nisin A producer) were sensitive at a high concentration of nisin variants including their own products. The growth of Gram-negative bacterium, Escherichia coli was also inhibited by high concentration of nisin, although nisin producers and Gram-negative bacteria are generally resistant to nisin variants.