Horizontal gene transfer (HGT) of mobile genetic elements (MGEs) plays a key role in bacterial evolution and is a key driver of the emergence and spread of new bacterial pathogens. Recently, we have shown that wall teichoic acid (WTA) structures govern phage-mediated high efficiency horizontal transfer of S. aureus pathogenicity islands (SaPIs) among major Gram-positive pathogens (1). Accounting for over 50% of the cell wall mass, WTAs are the most abundant surface molecules in the cell wall of S. aureus. Elucidation of the molecular recognition mechanisms underlying phage/S. aureus interactions involving WTA is critical in mapping the routes of phage-dependent horizontal gene transfer. Here we our report the identification of the receptor-binding protein (RBP) Gp45 from phage phi11, which is known for its high transducing efficiency and is often used as a model phage to study horizontal transfer of resistance and virulence genes. Moreover, we demonstrate that GlcNAc residues on WTAs and O-acetyl groups at the 6-position of muramic acid residues in peptidoglycan are essential components of the phi11 receptor. The identification of the phi11 RBP and characterization of the major components of its receptor in the cell wall enhance our understanding of horizontal gene transfer mediated by S. aureus phages and provide novel insights into critical functions of WTAs in microbe-host interaction, which involves multivalent protein-carbohydrate interactions. Our results also provide new tools for labeling the subdomain structures in S. aureus cell wall and establish a solid basis for the development of sensitive affinity-based infection diagnostics and therapeutics for MRSA infection (2).

Ref:
1)Winstel V, Liang C, et al (2013) Wall teichoic acid structure governs horizontal gene transfer between major bacterial pathogens. Nat. Commu 4: Article number 2345.

2) Li X , Koc C, et al. 2016, An essential role for the baseplate protein Gp45 in phage adsorption to Staphylococcus aureus (in press, Sci Rep )