PFGE profiles of Lactococcus lactis LMG2081 and lacticin LMG and lactococcin G mutants (A) and Southern blot hybridization with a lmgM probe (B). Total DNA from Lactococcus lactis LMG2081 (lanes 1, 5, 8, and 12), LMG2081/pG+host9lctLMG (lanes 2, 6, 9, and 13), or LMG2081/pG+host9lcnG (lanes 3, 7, 10, and 14) was digested with NotI (lanes 1 to 3) or SmaI (lanes 5 to 7), not digested (lanes 8 to 10), or treated with S1 nuclease (lanes 12 to 14). Lanes 4 and 11, λ concatemers. White arrows, linearized plasmids carrying the lctLMG operon; black arrows, differences in chromosomal fragments between the WT strain and the lactococcin G mutant.