Conjugal transfer in Lactococcus lactis of a 68-kilobase-pair chromosomal fragment containing the structural gene for the peptide bacteriocin nisin.

Nisin-producing transconjugants were generated by mating nisin-producing strains of Lactococcus lactis subsp. lactis with derivatives of L. lactis subsp. lactis LM0230. The sucrose-utilizing ability and reduced bacteriophage sensitivity were also transferred with the nisin-producing character. Pulsed-field gel electrophoretic analysis of genomic DNA from donor, recipient, and nisin-producing transconjugants indicated that 68 kbp of DNA was transferred from the chromosome of the donor into the chromosome of the recipient in the conjugation process. The location of the transferred nisin structural gene spaN in the transconjugant HID500 was not stable, and cultures of strain HID500 were a mixture of different genotypes in which spaN was located at different positions in the chromosome on different SmaI fragments. ApaI, BglI, BssHII, NciI, SalI, and SmaI digests of genomic DNA were used to map the location of spaN in a donor (DL11) and a nisin-producing transconjugant (HID504). Images