Creating broad host range phiX174 bacteriophage for Microviridae capsidlipopolysaccharide interaction investigation

Phage therapy that utilises natural and genetically engineered phages for medical treatment of antibiotic-resistant infections requires further experimental data on bacteriophages with an extended host range to produce more potent therapeutics and decrease their approval time. In this work, susceptibility to phiX174 was investigated for fourteen E. coli strains by bioinformatic analysis and microbiological methods. We confirm prior work showing K-12, B, Crooks, and Nissle 1917 strains of E. coli are not susceptible to phiX174 but reveal that an E. coli W strain is infectible. In addition, we demonstrate that R1 LPS outer core type structure is a predominant receptor for phiX174, however, not sufficient for the productive infection, and that phiX174 may be able to attach to O6-antigen and group 2 capsule suggesting it could infect potentially pathogenic E. coli strains. Finally, we extend the host range of phiX174 to E. coli Crooks through mutagenesis and show that it does not require any mutations within capsid genes but instead is enabled by variations in A/A*/D/E genes and J-F intergenic region, indicating that, at least within the Microviridae, the portion of the phage lifecycle that occurs within host cells may be as crucial for a host-range determination as capsid composition.