Assessing the biogeography of marine giant viruses in four oceanic transects

Abstract

Viruses of the phylum Nucleocytoviricota are ubiquitous in ocean waters and play important roles in shaping the dynamics of marine ecosystems. In this study, we leveraged the bioGEOTRACES metagenomic dataset collected across the Atlantic and Pacific Oceans to investigate the biogeography of these viruses in marine environments. We identified 330 viral genomes, including 212 in the order Imitervirales and 54 in the order Algavirales. We found that most viruses appeared to be prevalent in shallow waters (<150 m), and that viruses of the Mesomimiviridae (Imitervirales) and Prasinoviridae (Algavirales) are by far the most abundant and diverse groups in our survey. Five mesomimiviruses and one prasinovirus are particularly widespread in oligotrophic waters; annotation of these genomes revealed common stress response systems, photosynthesis-associated genes, and oxidative stress modulation genes that may be key to their broad distribution in the pelagic ocean. We identified a latitudinal pattern in viral diversity in one cruise that traversed the North and South Atlantic Ocean, with viral diversity peaking at high latitudes of the northern hemisphere. Community analyses revealed three distinct Nucleocytoviricota communities across latitudes, categorized by latitudinal distance towards the equator. Our results contribute to the understanding of the biogeography of these viruses in marine systems.

Metatranscriptomics reveals declines in ice cover influence winter viral community activity

“…The NCLDV MCP detected in the winter libraries (427 sequences) represented five of the six established NCLDV orders (Figure 1C) (71), most of which were assigned to the Imitervirales (395 sequences) (Table S3). The relatively higher Imitervirales MCP richness may reflect the broad host range of this group (92, 93). The phylogenetic diversity of RdRp present in the winter libraries (332 sequences) was similarly high, spanning the known phylum-level diversity of the Orthornavirae (Figure 1D, Table S3).…”

Phylogenetic diversity and functional potential of large and cell-associated viruses in the Bay of Bengal

“…While only Cox’s Bazar samples had a high enough abundance of NCLDVs to recover MAGs, NCLDV contigs were still found in Saint Martin, and we cannot rule out the possibility that biases in assembly or sequencing may have hidden more NCLDV MAGs from Saint Martin. The majority of mcp s found in the data are from the orders Algavirales and Imitervirales, which are the two largest orders of NCLDVs and are generally the most abundant in coastal waters ( 87 ). The large genomes of NCLDVs have been shown to greatly alter host metabolism as they contain many genes that mimic host homologs and can hijack host machinery to turn the host’s metabolism towardmaking viruses ( 24 ).…”

Virologs, viral mimicry, and virocell metabolism: the expanding scale of cellular functions encoded in the complex genomes of giant viruses

“…Multiple studies have identified homologs of rhodopsins in the genomes of giant viruses, including several members of the Imitervirales (Needham et al 2019 , Moniruzzaman et al 2020a , Farzad et al 2022 ). Moreover, several environmental surveys have found that viral rhodopsins are widespread in marine environments (Yutin and Koonin 2012b , Philosof and Béjà 2013 , López et al 2017 , Olson et al 2018 , Ha et al 2023 ). Viral rhodopsins fall into several distinct groups and have been acquired from cellular lineages multiple times independently.…”