Bacteriophages that infect marine roseobacters: genomics and ecology.

Viruses are the most abundant biological entities in seawater. They influence microbial population dynamics, genetic heterogeneity and biogeochemical cycles in marine ecosystems. The isolation and characterization of viruses that infect specific hosts have greatly advanced our knowledge of the biological and ecological interactions between viruses and their hosts. Marine Roseobacter are abundant, ubiquitous and diverse in the ocean and play active roles in global biogeochemical cycling, especially the sulfur cycle. Currently, 32 bacteriophages that infect multiple lineages of roseobacters have been isolated and sequenced. These roseophages exhibit diverse morphologies, nucleic acid types and genomic features. Here, we provide the most up-to-date overview of roseophages. Most roseophages are host specific and have a wide range of genome sizes and open reading frames. Based on a genome-wide comparison, at least eight distinctly different types of roseophages were identified, indicating their diversity. Lysogenic-related and gene transfer agent-related genes are commonly found in roseophage genomes, implying the importance of genetic transfer within roseobacters. This feature could provide the versatility for roseobacters to quickly adapt to the changing environments. A wide distribution range of roseophages in the global ocean, especially in coastal environments, has been observed, reflecting the cosmopolitan nature of the Roseobacter lineage.