Eastern Tropical South Pacific viruses

Viruses play an important role in the ecology and biogeochemistry of marine ecosystems. Oxygen minimum zones (OMZs) are critically important to marine nitrogen cycling and global climate change. The microbial communities and their metabolic capabilities in these anoxic zones are relatively well-studied, while less is known about the role of viruses in shaping metabolic networks and ecological dynamics along redox gradients associated with OMZs. We identified over 46,000 unique viral populations (≥ 5kb) in 22 deeply sequenced seawater samples from 6 stations along a gradient of distinct oceanographic features in the Eastern Tropical South Pacific (ETSP) OMZ. Viral communities clustered into 6 groups that corresponded to distinct oceanographic features, with 3 clusters representing samples from anoxic waters. This exceeds the number of viruses previously recovered from the ETSP by at least an order of magnitude. Identified viral genomes among these communities encoded six N-cycle AMGs associated with denitrification, nitrification assimilatory nitrate reduction and nitrite transport. The majority of these AMGs (80%) were identified in large-genome T4-like Myoviridae phages, predicted to infect Cyanobacteria and Proteobacteria, or in unclassified archaeal viruses predicted to infect Thaumarchaeota.