The host range and the role of O-antigen in P1 transduction with its alternative S’ tail fibre

Abstract

Enterobacteria phage P1 expresses two types of tail fibre, S and S′. Despite the wide usage of phage P1 for transduction, the host range and the receptor for its alternative S prime tail fibre was never determined. Here, a ΔS-cin Δpac E. coli P1 lysogenic strain was generated to allow packaging of phagemid DNA into P1 phage having either S or S′ tail fibre. P1(S′) could transduce phagemid DNA into Shigella flexneri 2a 2457O, Shigella flexneri 5a M90T and Escherichia coli O3 efficiently. Mutational analysis of the O-antigen assembly genes and LPS inhibition assays indicated that P1(S′) transduction requires at least one O-antigen unit. E. coli O111:B4 LPS produced a high neutralising effect against P1(S′) transduction, indicating that this E. coli strain could be a host for P1(S′). Mutations in the O-antigen modification genes of S. flexneri 2a 2457O and S. flexneri 5a M90T did not cause significant changes to P1(S′) transduction efficiency. A higher transduction efficiency of P1(S′) improved the delivery of a cas9 antimicrobial phagemid into both S. flexneri 2457O and M90T. These findings provide novel insights into P1 tropism-switching, by identifying the host range of P1(S′) and demonstrating its potential for delivering a sequence-specific Cas9 antimicrobial into clinically relevant S. flexneri.