Novel insertion sequence-like element IS982 in lactococci

A novel insertion sequence-like (IS) element, designated IS982, was found on the lactose plasmid, pSK11L, from Lactococcus lactis subsp. cremoris SK11 and was located between the origin of replication and the oligopeptide transport gene cluster. The 1003-base pair (bp) IS982 was flanked by 18-bp perfect inverted repeats. IS982 contained an open reading frame encoding a putative transposase of 296 amino acids. An almost identical IS-like element (99% DNA sequence identity) was cloned and partially sequenced from the chromosome of Lactococcus lactis subsp. cremoris Wg2 with 17-bp perfect inverted repeats. Southern analysis indicated that in 12 lactococcal strains examined, IS982 was present with copy numbers ranging from 1 to at least 20. IS982 displayed sequence homology to the putative IS element RSBst-alpha from Bacillus stearothermophilus CU21, IS982 and RSBst-alpha were not related to other known insertion sequences and may represent a new family of IS elements.