Presentation of Three Novel Tailed Phages Targeting Multiple Strains of Pseudomonas syringae

Pseudomonas syringae are ubiquitous epiphytic plant pathogens infecting a wide range of important agricultural plant species. Bacteriophages has been proposed as biocontrol agents against plant pathogens, however, in order to utilize this approach, a deeper understanding of phage diversity and phage-host interactions is required. Phages targeting P. syringae GAW0113 were isolated from organic waste samples. Three distinct phage isolates were purified and subjected to whole-genome sequencing, comparative genomics, transmission electron microscopy and host-range assay using a wide selection of diverse P. syringae isolates. The three phage isolates, Pseudomonas phage Bertil, Misse, and Strit, were shown to have podovirus morphology with a short tail stub and isometric head. They had double-stranded DNA ranging from 41,342 to 41,374 bp in size comprising 50-51 open reading frames. The three phage genomes were highly similar and genomic comparison analyses showed that they all belong to the Autographiviridae family of the order Caudovirales. All three phages were shown to have a narrow host-range. The three phages were shown to share morphological and genomic features with other phages in the Autographiviridae family, however, based on the limited nucleotide similarity we propose that the phages constitute a novel genus. All three phages were found to infect multiple strains of P. syringae covering several phylogroups.