Identifying Phage Host Receptors Using TraDIS

The growing antimicrobial resistance crisis has sparked renewed interest in using bacteriophage (phage) as a treatment for antibiotic-resistant infections. Phage are viruses that infect and often kill bacteria, and have served as key models for many molecular biology studies. There are many complex phage-bacterial interactions that dictate the success or failure of the phage life cycle, but many of these are not well understood or characterised. These include the specific interactions to recognize a bacterium during the infection process, bacterial phage defence mechanisms and metabolic pathways that are key to phage replication. In this study a novel Escherichia coli phage, Arnold, is characterised and the genome sequence is reported. We then use transposon-directed insertion sequencing (TraDIS) to screen a library of E. coli mutants to identify over 200 genes involved in Arnold phage infection or in phage resistance. Using this approach, we identified both an outer membrane protein (BtuB, vitamin B12 transporter) and an inner membrane protein (SdaC, serine/proton symporter) involved in phage infection. Deletions in these genes were shown to provide immunity to infection by this phage. Understanding the genetic basis of phage infection and phage resistance should allow us to select or design phage to target specific bacterial pathogens in the future.