Characterization and genome analysis of a novel Stenotrophomonas maltophilia bacteriophage BUCT598 with extreme pH resistance

Stenotrophomonas maltophilia (S. maltophilia) is an important Gram-negative opportunistic pathogen that is widely distributed in nature. S. maltophilia is highly drug-resistant because of its intrinsic properties and acquired drug resistance involving multiple molecular mechanisms, which creates a critical situation for infection therapy. Hence, there is an urgent need for alternative antimicrobial strategies to combat S. maltophilia. Herein, a novel S. maltophilia bacteriophage (phage) in family Podoviridae, named BUCT598, was isolated from hospital sewage and characterized to evaluate its potential as an antibacterial agent. The one-step growth curve showed that its latent period and burst size were approximately 30 min and 165 PFU/cell, respectively. Furthermore, phage BUCT598 survived within an extremely broad pH range (1-11), indicating its outstanding tolerance to both extremely acidic and extremely alkaline conditions. The whole-genome sequence of phage BUCT598 showed that it was a linear double-stranded DNA genome of 43,581 bp and 60% GC content. We identified 55 putative gene products involved in DNA replication, packaging, structure, and cell lysis. Whole-genome sequence comparisons among closely related phages indicated that phage BUCT598 had the highest sequence similarity with S. maltophilia phage BUCT609, with 52% query coverage and 76.40% identity, suggesting that it is a novel phage. Our findings indicate the great potential of phage BUCT598 as an alternative antimicrobial agent to eliminate S. maltophilia, and provide additional evidence that will help to understand how phages adapt and evolve under extreme environmental conditions, thereby opening up more extensive biotechnology applications of phages.