The hypersaline northwestern Arabian Gulf contains a phylogenetically diverse and highly uneven community of viruses related to cyanophages and pelagiphages

Cyanobacteria are the dominant primary producers in many marine waters, and are intimately connected with the cyanophages that infect them. The most commonly isolated marine cyanophages form a monophyletic group based on several marker genes including g20, a gene that codes the capsid assembly protein. Based on morphology, these viruses are typically referred to as cyanomyoviruses. Here, we used g20 sequences to interrogate the diversity of cyanomyoviruses at 5 locations in the waters of the northwestern Arabian Gulf. The diversity and richness of g20 sequences varied among locations and were highest at the southernmost sites. Most sequences belonged to a small number of operational taxonomic units (OTUs), with the rest belonging to low abundance rare OTUs. Phylogenetic analysis revealed that the most abundant genotypes fell within the ubiquitous cyanomyovirus Cluster II, while others clustered with metagenome assembled pelagimyophage sequences and other environmental sequences across a broad diversity of clades. This study revealed a diverse community of cyanomyoviruses in the northwestern Arabian Gulf that is dominated by a few relatively abundant but phylogenetically diverse taxa.