Nucleotide sequence and analysis of the new chromosomal abortive infection gene abiN of Lactococcus lactis subsp. cremoris S114.

A 7.275-kb DNA fragment which encodes resistance by abortive infection (Abi+) to bacteriophage was cloned from Lactococcus lactis subsp. cremoris S114. The genetic determinant for abortive infection was subcloned from this fragment. This gene was found to confer a reduction in efficiency of plating and plaque size for prolate-headed bacteriophage phi 53 (group I homology) and for small isometric-headed bacteriophage phi 59 (group III homology). This new gene, termed abiN, is predicted to encode a polypeptide of 178 amino acid residues with a deduced molecular mass of 20,461 Da and an isoelectric point of 4.63. No homology with any previously described genes was found. A probe was used to determine the presence of this gene only in S114 from 31 strains tested.