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ABSTRACT 22 The molecular interactions between staphylococcal phages and host cell surfaces are poorly 23 understood. Employing Staphylococcus aureus teichoic acids mutants, we demonstrate that 24 wall teichoic acid (WTA) but not lipoteichoic acid (LTA) serves as a receptor for 25 staphylococcal siphovirus and myovirus while only the siphovirus requires glycosylated 26 WTA. 27 28 3 The horizontal transfer of virulence and resistance genes by bacteriophages has a profound 29 impact on the pathogenicity and environmental adaptation of Staphylococcus aureus and 30 other major human pathogens. The host range of a specific phage is largely determined by its 31 capacity to adsorb to cognate receptor structures on the bacterial cell surface. Understanding 32 the molecular determinants of host specificity is also critical for the design of phage therapies, 33 which are increasingly regarded as an alternative strategy to combat antibiotic-resistant 34 bacteria (16). However, while the receptors for many coliphages have been investigated in 3