The antibiotic peptide nisin produced by Lactococcus lactis is used as
a food preservative due to its activity against spores and vegetative
cells of Gram-positive bacteria. The post-translational maturation of
this secreted peptide includes dehydration of serine and threonine re
sidues, lanthionine formation and a proteolytic processing of 23 amino
acids from the N-terminus. Mutations in the nisZ, nisB and nisP genes
of the biosynthetic nisZBTCIPRK nisin operon were made by gene replac
ement or integration of a plasmid. The mutations caused a drastic decr
ease of the transcription from the promoters upstream of the nisZBTCIP
RK and nisFEG operons resulting in loss of nisin production and nisin
immunity. The transcription of the nisin operons and nisin immunity co
uld be partially restored by adding nisin to the growth medium of the
cells. Nisin induction of the mutant strains also increased the level
of the putative immunity NisI protein. These results showed that the n
isZBTCIPRk operon is positively autoregulated and that the nisFEG oper
on is in the same regulon.