Virus-Host Interactions Reveal Potential Roles Towards Phosphorus Cycling in South Atlantic Ocean Euphotic Zones

BackgroundDue to their role as obligate parasites of marine microorganisms, viruses are primary mediators of marine biogeochemical cycles. Recent studies have provided irrevocable evidence showing that viruses augment the metabolisms of bacteria and archaea through expression of auxiliary metabolic genes (AMGs). Several studies have shown that AMGs affect the biogeochemical recycling of sulphur and nitrogen but comparatively less is known regarding their influence on phosphorus recycling.ResultsHere, we provide the first insights regarding the potential effects of phosphorus limitation and AMGs on putative prokaryotic hosts in the euphotic zone of the South Atlantic Ocean (SAO). We identified 7,176 viral contigs that were clustered into 5,999 viral operational taxonomic units (vOTUs, >5kb). These SAO viral communities appear to be unique, as over 89% had no taxonomic assignment, possibly due to the genetic endemism in this ocean. Three phosphatases, phoN, gmhB and rnhA-cobC, were identified as P-cycle AMGs in both prokaryotic double-stranded DNA viruses and eukaryotic Nucleocytoplasmic Large DNA viruses. These genes are associated with the acquisition of inorganic phosphate from phosphate esters, the largest reservoir of P-containing compounds in the marine environment. AMGs were identified in both uncultured and unclassified prokaryotic double-stranded DNA viruses predicted to infect Bacteriodetes, Proteobacteria, Chloroflexota and Poseidonales lineages. ConclusionTogether, these results suggest that viruses modulate P-cycling in euphotic zones of the ocean and that the acquisition of these phosphatase genes may be cues of P-ester stress.