According to a new study published last week in the journal Science, it has been identified in the world’s oceans more than five thousand new types of viruses. The researchers analyzed tens of thousands of water samples from around the world for RNA viruses, viruses that use ribonucleic acid as genetic material.
A typical example of an RNA virus is the coronavirus SARS-CoV-2, which causes covid-19. The study authors believe that these viruses are understudied compared to DNA viruses, which use deoxyribonucleic acid as their genetic material.
Scientists want to double the number of strains
The diversity of newly discovered viruses is so great that scientists suggest double the number of taxonomic groups necessary to classify them among the current five to ten strains. “We wanted to systematically study them on a very large scale and explore an environment that no one has yet addressed in depth.” said Matthew Sullivan, professor of microbiology at Ohio State University.
According to Sullivan, research on RNA viruses to date has mostly focused on those that cause disease. Well-known RNA viruses include, for example, the influenza virus, Ebola or the aforementioned coronavirus. However, this is only a “small part” of the RNA viruses present on our planet.
As part of the study, researchers analyzed 35,000 water samples taken from 121 locations in the world’s five oceans. They studied genetic sequences obtained from small aquatic organisms known as plankton, which are common hosts for RNA viruses.
Search for a specific gene
They focused on sequences belonging to RNA viruses, looking for one of the oldest genes called RdRp, which is found in all RNA viruses, while it is absent in other viruses and cells. In the end, they identified more than 44,000 sequences with this gene.
Because RdRp probably exists since the appearance of life on Earthits position in the sequence differed several times, meaning that traditional phylogenetic tree relationships could not be described by sequences alone.
Researcher in the field of microbiology and co-author of the article Ahmed Zayed says: “RdRp is perhaps one of the oldest genes – it existed before DNA was needed. So we are not only tracking the origin of viruses, but also the origin of life.” New data on RdRp gene divergence over time, he believes, will provide insight into how early life on our planet may have evolved.
5,500 new RNA viruses
To organize the huge amount of data collected scientists used artificial intelligence in combination with traditional evolutionary trees and 3D representations of sequential structures. In this way, they ultimately identified about 5,500 new RNA virus species belonging to the five existing strains and the five newly designed strains, which the researchers named Taraviricota, Pomiviricota, Paraxenoviricota, Wamoviricota and Arctiviricota.
The largest collection of newly identified species belongs to the proposed strain of Taraviricota, which the scientists named after the Tara Oceans Consortium, which provided water samples. “The Taraviricota strain has been found across the ocean, indicating that it is ecologically important.” said Matthew Sullivan.
Taken together, these findings led scientists not only to design five new strains, but also to at least eleven novel orthornaviral classes of RNA viruses. Experts are currently preparing a proposal asking the International Virus Classification Committee to formalize the classification of new strains and classes.
Why check for viruses?
“It was necessary to compare knowledge to study the unknown”, said Sullivan. “We’ve created a reproducible way to compare these sequences so we can be sure we’re comparing positions that accurately reflect evolution.”
While microbes play a vital role in life on the planet, the viruses that infect or interact with them have different effects on microbial functions. We assume that these Types of viruses have three main functions: they kill cells, alter their energy management and transfer genes from one host to another.
According to the authors of the study, knowledge of the diversity and abundance of viruses in the world’s oceans will explain the role of marine microbes in the adaptation of the oceans to climate change. The oceans absorb half of the carbon dioxide produced by human activity in the atmosphere, and previous research has suggested that marine viruses are part of the “biological pump” that influences how carbon is stored.