Broad-host-range Kayvirus phages preferentially infect Staphylocococcus aureus cells with b-glycosylated WTA

WTA glycosylation plays a pivotal role in the survival of Staphylococcus aureus, by participating in the interaction with the immune system (both innate and adaptive) and in the adsorption of bacteriophages. In this species, virulent phages with podovirus morphology, as well as some myoviruses, are known to require ?-glycosylation (catalized by the product of gene tarS), and are hindered by a-glycosylation (carried out by protein TarM) of WTA. In contrast, other myophages, like phiIPLA-RODI and phage K, exhibit a broad-host range and can infect strains without either glycosylation according to the spot test. Here, we demonstrate that these two phages, belonging to the Kayvirus genus, do actually exhibit a preference regarding WTA glycosylation, being more efficient at infecting strains with tarS-mediated modifications. Moreover, in the case of phiIPLA-RODI, the presence of the gene tarM correlates with decreased susceptibility. As previously demonstrated for phage Stab20, mutations in the quorum-sensing system Agr confer reduced susceptibility. Additionally, we have found that the alternative sigma factor SigB affects tarS expression, modulating the infectivity of both phiIPLA-RODI and phage K, highlighting the tight control of this phenotype depending on the bacterial growth phase. Our results also indicate that capsule production has an impact on the ability of phiIPLA-RODI to kill S. aureus. The frequent isolation of strains lacking an intact tarM, together with the evidence that ?-glycosylated WTA is the most common variant in vivo, suggest that the majority of known virulent phages infecting S. aureus have evolved to maximize their chances of infecting this pathogen in the mammalian host. While this is good news from the perspective of phage therapy, the potential impact of altering the balance between phage and host by exposing cells to high doses of phages must be examined. Overall design: 6 samples were analyzed, correponding to 3 biological replicates of 24 hours biofilms formed by S. aureus RN4220 or SH1000 in TSBg