Isolation and genomic characterization of selective lytic Pseudomonas phage Amjad_SA from a desert urban pond in...

Bacteriophages are abundant and diverse components of aquatic ecosystems and contribute to the regulation of bacterial population dynamics. However, Pseudomonas-associated tailed bacteriophages from urban aquatic environments within arid regions remain insufficiently characterized.

We isolated and characterized Pseudomonas phage Amjad_SA, a lytic bacteriophage infecting a Pseudomonas isolate provisionally assigned to the Pseudomonas alcaligenes group (isolate 4L), recovered from an urban artificial pond in Riyadh, Saudi Arabia. The phage was analyzed using transmission electron microscopy (TEM), biological assays (host range, adsorption kinetics, one-step growth, and stability tests), and whole-genome sequencing followed by annotation and phylogenetic analysis.

Phage Amjad_SA exhibited lytic activity against the host isolate and did not infect other tested Gram-negative or Gram-positive bacterial species. TEM revealed an icosahedral head (47.5 ± 1.2 nm) and contractile tail (69.7 ± 1.1 nm), consistent with tailed double-stranded DNA bacteriophages within the class Caudoviricetes. Under the experimental conditions tested, the phage retained infectivity following incubation at 2565 °C and across pH 59. Genomic analysis showed a linear double-stranded DNA genome of 45,788 bp with a GC content of 60.4%, encoding 72 predicted open reading frames, including genes associated with genome replication, packaging, host lysis, and virion assembly. A single tRNA-Ser (aga) gene was identified, while a substantial proportion of ORFs were annotated as hypothetical proteins.

These findings provide a comprehensive biological and genomic profile of phage Amjad_SA and expand the available reference framework for Pseudomonas-infecting tailed bacteriophages recovered from urban aquatic environments within arid regions.