Bacteriophage interactions with enteric pathogens

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Project Summary How phages and viruses recognize their specific host cell receptors is not known for the vast majority of species. The long-term goal is to understand the general principles behind the structures and mechanisms that control host cell entry for bacteriophages. The objective of this proposal is to determine the structures, and mechanisms of how phages use both outer and inner membrane proteins for infection in enteric pathogens such as Shigella, E.coli and Salmonella. The central hypothesis is that there are conserved protein structures and corresponding mechanisms that govern phage entry for the majority of phage:host pairs. We predict that there are universal cell surface features that are generally required for phage entry, and also other cell surface features that may be specific to individual phage:host pairs. The rationale underlying the proposed work is that we will identify key receptor proteins in enteric pathogens that mediate phage infection, and that a better understanding of these interactions will provide physical targets for either identifying new therapies or improving existing ones. We will pursue this research using a combination of conceptual and technological innovations involving genetics, biochemistry and biophysics. These include innovations recently developed in my laboratory, as well as more established microbiological techniques. The proposed research is significant, as it will provide both structural and mechanistic insights into how phages dock to their specific hosts, a necessary step for productive infection. This work will also develop resources that will be used by other researchers. For example, the proposed work will develop widely-applicable complex transposon and single gene deletion libraries, which will greatly propel research forward in Shigella, as currently no such genetic toolkit exists. The expected outcome of this work will provide a basic understanding of how phages attach to hosts including which proteins and interactions are universally required, and which are specific to individual phage:host pairs. Additionally, we will gain an atomic level understanding of the protein:protein binding interactions and transient infection intermediate states that control infection. Atomic level details, such as how phages bind to their hosts are critical for engineering new therapeutics or enhancing existing ones.