Structure and host specificity ofStaphylococcus epidermidisbacteriophage Andhra

Staphylococcus epidermidis is an opportunistic pathogen of the human skin, often associated with infections of implanted medical devices. An increase in antibiotic resistance in S. epidermidis and other bacterial pathogens has led to renewed interest in the use of bacteriophages as an alternative to conventional antibiotics. Staphylococcal picoviruses are a group of strictly lytic, short-tailed bacteriophages with compact genomes that are attractive candidates for therapeutic use. Here, we report the structure of the complete virion of S. epidermidis -infecting phage Andhra, determined using high-resolution cryo-electron microscopy, allowing atomic modeling of the capsid and tail proteins, including twelve trimers of a unique receptor binding protein, the hexameric tail knob that acts as a gatekeeper for DNA ejection, and the tail tip, which is a heterooctamer of two different lytic proteins. Our findings elucidate critical features that enable host recognition and penetration, facilitating the development of this group of phages for therapeutic applications.