Bacteriophage specificity is impacted by interactions between bacteria.
Bacteriophage display a great deal of diversity in specificity, or how many different types of hosts they can infect. This study uses mathematical modeling and an in vitro system consisting of Escherichia coli, Salmonella enterica, a novel T5-like generalist phage, and the specialist phage P22vir to understand what generates this diversity. Results suggest that bacteriophage specificity is impacted by the interactions between bacterial hosts, with competing bacteria favoring bacteriophage with broad host ranges and bacteria that engage in mutualism favoring specialist bacteriophage. This study will improve our ability to use bacteriophage to control antibiotic resistant infections when pathogens are engaged in interactions.