Novel P335-like Phage Resistance Arises from Deletion within Putative Autolysin in .

and are broadly utilized as starter cultures for fermented dairy products and are inherently impacted by bacteriophage (phage) attacks in the industrial environment. Consequently, the generation of bacteriophage-insensitive mutants (BIMs) is a standard approach for addressing phage susceptibility in dairy starter strains. In this study, we characterized spontaneous BIMs of DGCC12699 that gained resistance against homologous P335-like phages. Phage resistance was found to result from mutations in the YjdB domain of a putative autolysin gene. We further observed that alteration of a fused tail-associated lysin-receptor binding protein (Tal-RBP) in the phage restored infectivity on the BIMs. Additional investigation found homologs to be widespread in and and that different homologs are highly correlated with cell wall polysaccharide (CWPS) type/subtype. CWPS are known lactococcal phage receptors, and we found that truncation of a glycosyltransferase in the operon also resulted in resistance to these P335-like phages. However, characterization of the CWPS mutant identified notable differences from the mutants, suggesting the two resistance mechanisms are distinct. As phage resistance correlated with mutation has not been previously described in , this study offers insight into a novel gene involved in lactococcal phage sensitivity.