Roseobacter clade bacteria are key players in marine ecosystems, contributing significantly to carbon and sulfur cycles. Marine viruses, particularly those targeting Roseobacter, play crucial roles in regulating microbial communities and biogeochemical processes. Despite their importance, phages infecting the Roseobacter clade remain poorly understood. In this study, a novel siphophage, vB_DshS-R26L, infecting Dinoroseobacter shibae DFL12^T was isolated and characterized for its physiological and genomic properties. Phage R26L was isolated from seawater samples collected in the Pearl River Estuary using the double-layer agar method. R26L is a siphovirus with a long, non-flexible tail and an elongated head. The phage has a narrow host range and demonstrates a long infection cycle with a latent period of 7 hours and a burst size of 22 plaque-forming units (PFU cell^-1). R26L possesses a circular, double-stranded DNA genome of 79,534 base pairs with a G + C content of 62.59%, encoding 116 open reading frames (ORFs). Seven auxiliary metabolic genes (AMGs), including those related to phosphate metabolism and queuosine biosynthesis, were identified, that R26L may influence host metabolism during infection. Genomic and taxonomic analyses revealed that R26L shows homology and synteny with two phages from different Phylum infecting Roseobacter and Pseudanabaena, respectively. But given that the highest intergenomic similarity is only 54.7%, we propose that represents a new genus within the Siphoviridae family. The ability of R26L to regulate host metabolism and facilitate gene transfer underscores its significant in microbial ecosystems, environmental nutrient cycling, and species or phyla evolution.
 

Roseobacter, bacteriophage, biological features, genomic analysis, auxiliary metabolic genes, rvolutionary trace