Taxonomic and functional characterization of vB_PaeS_GZMU_S12, a novel genus of temperate phage targeting Pseudomonas aeruginosa with broad-spectrum lytic and antibiofilm activities

Phage therapy is a promising alternative strategy for treating infections caused by multidrug-resistant (MDR) Pseudomonas aeruginosa (P. aeruginosa) , which urgently requires alternative therapies especially due to its ability to form persistent biofilms. In this study, a novel temperate phage, named vB_PaeS_GZMU_S12, was isolated and comprehensively characterized. Despite its temperate genomic features, it exhibited broad-spectrum lytic activity and effective antibiofilm effects. The phage demonstrated lytic activity against 30 out of 72 tested P. aeruginosa strains, resulting in a lytic rate of 41.7%. It maintained high stability across a broad temperature range of 4 to 50 °C and a pH range of 4 to 12. The lytic activity of phage S12 was dependent on MOI and significantly inhibited biofilm formation at high MOI. The maximum biofilm inhibition rate of 51.86% was achieved at an MOI of 10. The highest genomic similarity observed for phage S12 was 47.2%, with Pseudomonas phage Haboob (GenBank accession: OR683404.1). This value is well below the 70% threshold recommended by the International Committee on Taxonomy of Viruses (ICTV) for inter-genus demarcation. Based on phylogenetic tree analysis and comparative bioinformatics analyses, we propose that S12 represents a novel genus, for which we suggest the name “ Guangyivirus ”. The isolation and characterization of this novel P. aeruginosa phage contribute to our understanding of phage diversity and taxonomy, and provide a promising candidate for future exploration in phage-based therapeutics against antibiotic-resistant bacterial infections.