Pseudomonas Phage Lydia and the Evolution of the Mesyanzhinovviridae Family

Phage Lydia, a newly isolated siphovirus infecting <i>Pseudomonas aeruginosa</i>, was characterized with respect to its basic kinetic properties and subjected to comparative bioinformatic analysis with related phages. The phage exhibited a restricted host range, with lytic activity observed against 7 of 30 tested isolates. The genome of phage Lydia consists of a 61,986 bp dsDNA molecule and contains 89 predicted genes. Bioinformatic analysis suggests the presence of a DNA modification system, but no apparent genes associated with lysogeny or antibiotic resistance were identified. Taxonomic classification places Lydia within the <i>Mesyanzhinovviridae</i> family, <i>Rabinowitzvirinae</i> subfamily, and Yuavirus genus, with the closest relation to <i>Pseudomonas</i> virus M6. Comprehensive bioinformatic studies, including structural modelling and analysis of phage proteins, as well as comparative taxonomic, phylogenomic, and pangenomic analyses of the <i>Mesyanzhinovviridae</i> family, revealed relationships between proteins of <i>Mesyanzhinovviridae</i> phages, proteins from other phage groups, encapsulins, and a gene transfer agent (GTA) particle from <i>Rhodobacter capsulatus</i>. These analyses uncovered patterns of evolutionary history within the family, characterized by genetic exchange events alongside the maintenance of a common genomic architecture, leading to the emergence of new groups within the family.