Stabilization of the Lactococcus lactis nisin production transposon as a plasmid

Abstract

A transposon (Tn Nip) encoding nisin production was visualized and stabilized as a plasmid of approximately 60 kb in the transconjugant, LM0230Fus(Tn Nip), formed from a conjugation between nisin-producing Lactococcus lactis subsp. lactis LL33-1 and a plasmid-free LM0230 derivative. The plasmid did not correspond in size to any of the plasmids resident in the donor. A plasmid-cured derivative of this construct was also able to stabilize the transposon, as a plasmid, from all donors used. Therefore, for the first time, a host has been identified that can maintain the Tn Nip transposons stably excised out of the chromosome. The plasmid DNA was isolated and characterized by restriction digestion and was used to successfully transform cells, thus linking the nisin production phenotype to the plasmid.