◆Research findings by a group led by Associate Professor Tomoyo Okumura of the International Research Institute for Marine Core Samples have been published in *Nature Microbiology*
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Third RNA virus lineage discovered in extreme environments
A research paper by a group led by Associate Professor Tomoyo Okumura of the International Research Institute for Marine Core Samples was published in *Nature Microbiology* on January 17, 2024.
Hundreds of thousands of species of RNA viruses (*1) are known to exist on Earth, and many of them parasitize microorganisms. However, the diversity, evolution, and ecological roles of RNA viruses have not yet been fully elucidated.
In this study, using a proprietary detection method capable of accurately capturing RNA viral genomic information, we discovered the genome of a completely novel RNA virus within a community of hyperthermophilic microorganisms closely related to the last universal common ancestor, found in the high-temperature acidic springs of the Unzen and Kirishima fumarole zones. We have named this RNA virus Hot Spring RNA Virus (HsRV).HsRV is presumed to use thermophilic, acidophilic bacteria as hosts, and this discovery implies that RNA viruses inhabit high-temperature environments—the very settings believed to be the birthplace of life. Furthermore, the genetic sequence of HsRV differs significantly from those of the two known RNA virus kingdoms, suggesting the possibility of a third, distinct RNA virus kingdom.
Going forward, our research group plans to isolate and culture host strains harboring HsRV to elucidate the virus’s morphology and ecology. We also intend to apply the detection methods used in this study to various microorganisms, plants, and animals to further the search for unknown RNA viruses.
[Title] Double-stranded RNA sequencing reveals distinct riboviruses associated with thermoacidophilic bacteria from hot springs in Japan
(Discovery of a New RNA Virus Derived from Microorganisms in Hot, Acidic Hot Springs)
[Authors] S. Urayama, A. Fukudome, M. Hirai, T. Okumura, Y. Nishimura, Y. Takaki, N. Kurosawa, E. V. Koonin, M. Krupovic, and T. Nunoura
[Publication] Nature Microbiology
[Date Published] January 17, 2024
*1 RNA viruses: A general term for viruses that store their genome (blueprint) in RNA. They replicate themselves within host cells by utilizing the cells’ mechanisms. While they are well known as pathogens, such as coronaviruses, only a very small fraction of the diverse RNA viruses found on Earth are pathogenic.