Uncovering the determinants of model Escherichia coli strain C600 susceptibility and resistance to lytic T4-like and T7-like phage.

As antimicrobial resistance (AMR) continues to increase, the therapeutic use of phages has re-emerged as an attractive alternative. However, knowledge of phage resistance development and bacterium-phage interaction complexity are still not fully interpreted. In this study, two lytic T4-like and T7-like phage infecting model Escherichia coli strain C600 are selected, and host genetic determinants involved in phage susceptibility and resistance are also identified using TraDIS strategy. Isolation and identification of the lytic T7-like show that though it belongs to the phage T7 family, genes encoding replication and transcription protein exhibit high differences. The TraDIS results identify a huge number of previously unidentified genes involved in phage infection, and a subset (six in susceptibility and nine in resistance) are shared under pressure of the two kinds of lytic phage. Susceptible gene wbbL has the highest value and implies the important role in phage susceptibility. Importantly, two susceptible genes QseE (QseE/QseF) and RstB (RstB/RstA), encoding the similar two-component system sensor histidine kinase (HKs), also identified. Conversely and strangely, outer membrane protein gene ompW, unlike the gene ompC encoding receptor protein of T4 phage, was shown to provide phage resistance. Overall, this study exploited a genome-wide fitness assay to uncover susceptibility and resistant genes, even the shared genes, important for the E. coli strain of both most popular high lytic T4-like and T7-like phages. This knowledge of the genetic determinants can be further used to analysis the behind function signatures to screen the potential agents to aid phage killing of MDR pathogens, which will greatly be valuable in improving the phage therapy outcome in fighting with microbial resistance.