The ability of the plasmid-encoded restriction and modification system LlaBIII to protect Lactococcus lactis against bacteriophages

Aims: To investigate the potential of the plasmid-encoded restriction and modification (R/M) system LlaBIII to protect Lactococcua lactis against bacteriophages during milk fermentations. Methods and Results: The R/M system LlaBIII on plasmid pJW566 was cloned with a chloramphenicol cassette, resulting in plasmid pJK1. When introduced into L. lactis strains, pJK1 conferred increased phage resistance against the three most common lactococcal phage species 936, c2, and P335 and three unclassified industrial phages. The growth of the strains in RSM was not affected by the presence of plasmid pJK1. Conclusions: The plasmid-encoded R/M system LlaBIII has great ability to protect L. lactis strains against bacteriophages in milk fermentations. Significance and Impact of the Study: This study evaluates the ability of the LlaBIII R/M system to function as a phage defence mechanism which is an essential step prior to considering utilizing it for improving starter cultures.