Characterization of Pseudomonas aeruginosa Phage C11 and Identification of Host Genes Required for Virion Maturation.

Xiaoli Cui,Xiaojing Yang,Jiajia You,Tian Zhang,Hongjiang Yang,Fenjiao Zhang,Xuewei Pan,Kechong Huang,Yang He,Li Sun

doi:10.1038/srep39130

Xiaoli Cui, Xiaojing Yang + Show 8 more

Open Access

https://doi.org/10.1038/srep39130

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Abstract

The underlying mechanisms of phage-host interactions largely remained to be elucidated. In this work, Pseudomonas aeruginosa phage C11 was first characterized as a Myoviridae virus having a linear dsDNA molecule of 94109 bp with 1173 bp identical terminal direct repeats (TDR). Then the mutants resistant to phage C11 were screened in a Tn5G transposon mutant library of P. aeruginosa PAK, including two mutants with decreased adsorption rates (DAR) and five mutants with wild-type adsorption rates (WAR). When the WAR mutants were incubated with phage C11, their growth rates were significantly inhibited; the replication of the phage genomic DNA was detected in all the WAR mutants with the real-time quantitative PCR analysis; and the synthesized phage genomic DNA was processed into monomers for packaging evidenced by the southern blot analysis. Moreover, with strain PAK as indicator, small quantities of phage C11 were synthesized in the WAR mutants. Taken together, these data suggested the identified genes of the WAR mutants are necessary for efficient synthesis of the infectious phage particles. Finally, the WAR mutants were detected sensitive to two other Pseudomonas phages closely related with C11, further implying the evolved diversity and complexity of the phage-host interactions in both sides.

Highlights

Phage therapy shows great promises in combating bacterial infections[1,2]
The images showed that phage C11 had an icosahedral head of 65 nm in diameter and a long contractile tail with a length of 122 nm, indicating that phage C11 can be tentatively classified into the family Myoviridae (Fig. 1A)
The infectivity of phage C11 was characterized by one-step growth experiment at a multiplicity of infection (MOI) of 0.001

Summary

Introduction

Phage therapy shows great promises in combating bacterial infections[1,2]. Candidate phages used for treatments are usually selected mainly based on their host ranges. A number of mechanisms have been found contributing the defense of phage attacks in many bacteria[5,6] All these involved pathways are employed by diverse bacteria strains in the active strategies against phage infections. The Keio collection was used to identify bacterial genes involved in the λphage infection process. Phage receptor related genes were screened in E. coli phage mEp213 infection by employing a novel strategy to select bacterial cell-envelope mutants resistant to phage infection[9]. In screening phage JG004 resistant mutants, the gene speD encoding S-adenosylmethionine decarboxylase proenzyme for polyamine biosynthesis was identified, and the enzyme is possibly involved in the phage genome packaging process by affecting the charge density of the genomic DNA molecules[32]

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