Diversity, distribution and ecological potential of Oceanospirillales-associated viruses in the global ocean

Species of the bacterial Order Oceanospirillales are widely distributed in marine environments and play a crucial role in the bioremediation of hydrocarbon pollution. However, the identity and role of viruses linked to this bacterial group is still unclear. In this study, 3,273 viral contigs linked to Oceanospirillales were identified from more than 15 million viral and bacterial genomes and genome fragments, including 783 high-quality genomes of Oceanospirillales-associated viruses. Most Oceanospirillales-associated viruses are head-tail and filamentous viruses (n=549 and 17, respectively). A total of 1,226 putative auxiliary metabolic genes (AMGs) were annotated and these were involved in 39 main metabolic categories. Notably, 54 of these putative AMGs were associated with the degradation of aliphatic hydrocarbons, aromatic hydrocarbons and their derivatives, highlighting the potential roles of these viruses in hydrocarbon biodegradation. From the phylogenetic inference and structural similarity network, genes related to hydrocarbon and hydrocarbon-derivative degradation by viruses and hosts showed a convergent evolution. Based on the biogeographical analysis, most Oceanospirillales-associated viruses have been found in aquatic environments, with the highest abundance in temperate and tropical marine epipelagic zones. This study reveals the diversity, distribution and ecological potentials of Oceanospirillales-associated viruses, and emphasizes the need to incorporate them into an assessment of global hydrocarbon degradation.