Taxon Richness of “Megaviridae” Exceeds those of Bacteria and Archaea in the Ocean

• Published in: Microbes and Environments Vol. 33; no. 2; pp. 162 - 171
• Main Authors: Koyano, Hitoshi, Mihara, Tomoko, Goto, Susumu, Ogata, Hiroyuki, Grimsley, Nigel, Hingamp, Pascal
• Format: Journal Article
• Language: English
• Published: Japan Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles 2018; Japan Science and Technology Agency; Nakanishi Printing Co; the Japanese Society of Microbial Ecology (JSME)/the Japanese Society of Soil Microbiology (JSSM)/the Taiwan Society of Microbial Ecology (TSME)/the Japanese Society of Plant Microbe Interactions (JSPMI)
• Subjects: Archaea; Bacteria; Biodiversity; Deoxyribonucleic acid; DNA; DNA-directed RNA polymerase; Domains; Evolutionary genetics; Genomics; Life Sciences; Megaviridae; Microbiology and Parasitology; Microorganisms; Mimiviridae; Nucleic acids; ocean metagenome; Phylogenetics; Phylogeny; Protists; RNA; RNA polymerase; species richness; Systematics, Phylogenetics and taxonomy; Virology; Viruses; species richness; RNA polymerase; ocean metagenome; Megaviridae; Mimiviridae
• ISSN: 1342-6311; 1347-4405
• DOI: 10.1264/jsme2.ME17203

Since the discovery of the giant mimivirus, evolutionarily related viruses have been isolated or identified from various environments. Phylogenetic analyses of this group of viruses, tentatively referred to as the family “Megaviridae”, suggest that it has an ancient origin that may predate the emergence of major eukaryotic lineages. Environmental genomics has since revealed that Megaviridae represents one of the most abundant and diverse groups of viruses in the ocean. In the present study, we compared the taxon richness and phylogenetic diversity of Megaviridae, Bacteria, and Archaea using DNA-dependent RNA polymerase as a common marker gene. By leveraging existing microbial metagenomic data, we found higher richness and phylogenetic diversity in this single viral family than in the two prokaryotic domains. We also obtained results showing that the evolutionary rate alone cannot account for the observed high diversity of Megaviridae lineages. These results suggest that the Megaviridae family has a deep co-evolutionary history with diverse marine protists since the early “Big-Bang” radiation of the eukaryotic tree of life.