Genomic analysis of Synechococcus phage S-B43 and its adaption to the coastal environment

<p><em>Synechococcus</em> dominate picocyanobacterial communities in coastal environments. However, only a few <em>Synechococcus</em> phages have been described from the coastal seas of the Northwest Pacific Ocean. Here a new <em>Synechococcus</em> phage, S-B43 was isolated from the Bohai Sea, a semi-closed coastal sea of the Northwest Pacific Ocean. S-B43 is a member of <em>Myoviridae</em>, containing 275 predicted open reading frames. Fourteen auxiliary metabolic genes (AMG) were identified from the genome of S-B43, including five photosynthetic associated genes and several AMGs related to its adaption to the high turbidity and eutrophic coastal environment with a low ratio of phosphorus to nitrogen (HNLP). The occurrences of 31 AMGs among 34 cyanophage genomes indicates that AMGs <em>zwf</em>, <em>gnd</em>, <em>speD</em>, <em>petF</em> and those coding for FECH and thioredoxin were more common in coastal areas than in the open ocean and AMGs <em>pebS</em> and <em>ho1</em> were more prevalent in the open ocean. The occurrence of cyanophage AMGs in different environments might be a reflection of the environmental adaption of their hosts. This study contributes to our understanding of the interactions between cyanobacteria and cyanophages and their environmental adaption to the coastal environment.</p>