Phage resistance in Lactococcus lactis subsp. lactis strains isolated from traditional fermented milk products in Turkey

Lactococcus lactis subsp. lactis strains isolated from traditional fermented milk products in Turkey were used to determine their phage resistance against three different lactic phages. The following modes of action were examined: phage adsorption inhibition in five strains, abortive infection (heat sensitive phage resistance) in three strains, restriction/modification in four strains and blocking of phage DNA injection in one strain. The genetic nature of the phage resistance systems in these strains was determined by comparison of phage proliferation parameters, e.g. adsorption (%), EOP, burst size, latent period and production of major capsid protein, between wild-type strains and their plasmid-cured derivatives.