Isolation and characterization of PaP6, a newly isolated Pseudomonas aeruginosa bacteriophage containing three dsRNA genomic segments

Abstract:

[Objective] To characterize a novel Pseudomonas aeruginosa phage PaP6 via its biological properties. [Methods] Double-layer agar culture method was applied to observe the plaques of PaP6. Phage particles were examined by electron microscopy after cesium chloride density gradient centrifugation. PaP6 genome was extracted and digested with either DNase or RNase. Phage and host were mixed with multiplicity of infection (MOI) 10, 1, 0.1, 0.01, 0.001 and 0.000 1 respectively. Phage titers were measured after bacteria lysis. For one step growth experiments, phage and host with an MOI of 10 were used. The host range of PaP6 was tested with 112 Pseudomonas aeruginosa clinical isolates strains. [Results] The plaque of PaP6 was transparent and the edge of the plaque was clear. Its diameter was about 2 to 4 mm. PaP6 phage had an isometric head approximately 45 nm in diameter. Enzyme digestion experiment shows that PaP6 contained three double-stranded RNA segments. Infecting host bacteria with MOI of 0.1 gave the highest phage offspring. Phage growth characteristics were determined by one step growth curve. PaP6 infects 40.1% of Pseudomonas aeruginosa clinical isolated strains. [Conclusion] PaP6 genome is composed of three dsRNA segments, and it is the first reported Cystoviridae phage that infects Pseudomonas aeruginosa. The host range of PaP6 is wide, which implies its potential in phage therapy.