Isolation, characterization, and whole-genome analysis of the novel temperate bacteriophage Ph-p5 infecting...

Bacteria of the genus Glutamicibacter, due to their ubiquity, nutritional versatility, and ability to adapt to environmental stresses, play an important role in natural ecosystems and have been extensively studied. Nevertheless, there remains a significant gap in our knowledge regarding Glutamicibacter phages, particularly in comparison to those of the related actinobacteria. To date, only two virulent phages infecting G. arilaitensis have been described. To our knowledge, this is the first report on the isolation, characterization, and genome analysis of a temperate phage targeting G. halophytocola, an endophytic bacterium known for its plant-growth-promoting effect. The phage Ph-p5, with siphovirus structure, was isolated from soil. It exhibited a long latent period (120 min), a moderate burst size (87 ± 3 PFU/infected cell), and stability over a wide range of pH and temperature. The circularly permuted linear double-stranded DNA genome of phage Ph-p5, comprising 43,694 bp with a G + C content of 57.1%, contains 65 putative protein-coding sequences and one sequence encoding tRNA. Of the identified open reading frames, 33 were of unknown function, while the remaining ones were grouped into functional modules, including structural proteins, DNA replication and regulation, lysogeny, and lysis. The presence of intact lysogeny-related genes, together with the capacity for lysogenisation of the host strain G. halophytocola BIM B-1594, provides evidence that Ph-p5 is a temperate phage. Phylogenetic analysis demonstrated that phage Ph-p5 belongs to the class Caudoviricetes but exhibits significant divergence from known phages and may be assigned to a new genus, for which we propose the name "Petuglutavirus".