Spontaneous deletion mutants of the Lactococcus lactis temperate bacteriophage BK5-T and localization of the BK5-T attP site.

Spontaneous deletion mutants of the temperate lactococcal bacteriophage BK5-T were obtained when the phage was grown vegetatively on the indicator strain Lactococcus lactis subsp. cremoris H2. One deletion mutant was unable to form stable lysogens, and analysis of this mutant led to the identification of the BK5-T attP site and the integrase gene (int). The core sequences of the BK5-T attP and host attB regions are conserved in a number of lactococcal phages and L. lactis strains.