Researchers have identified more than 5,500 new viruses in the ocean, including a missing link in viral evolution


RNA viruses can cause deadly diseases. But they also play a vital role in ecosystems because they can infect a wide range of organisms, including microbes that influence environments and food webs at the chemical level.

the Research paper is a brief overview of some interesting scholarly work.

The big idea

Diagram of the biological classification system, showing that the phylum is a large grouping. VectorMine/iStock via Getty Images Plus

An analysis of genetic material in the ocean has identified thousands of previously unknown RNA viruses and doubled the number of phyla, or biological groups, of viruses thought to exist, according to a new study. our team of researchers published in the journal Science.

RNA virus are best known for diseases they cause in humans, ranging from the common cold to COVID-19. They also infect plants and animals important to people.

These viruses carry their genetic information in RNA rather than DNA. RNA virus evolve at much faster rates than DNA viruses. While scientists have cataloged hundreds of thousands of DNA viruses in their natural ecosystems, RNA viruses have been relatively little studied.

Line drawing of marine RNA viruses
There are more RNA viruses in the oceans than researchers previously thought. Guillermo Dominguez Huerta, CC BY-ND

Unlike humans and other cellular organisms, however, viruses lack unique short stretches of DNA that could act as what researchers call a genetic barcode. Without this barcode, trying to distinguish between different virus species in the wild can be difficult.

To circumvent this limitation, we decided to identify the gene that codes for a particular protein that allows a virus to replicate its genetic material. It is the one protein that all RNA viruses share, as it plays a critical role in how they spread.

However, each RNA virus has small differences in the gene that codes for the protein that can help distinguish one type of virus from another.

We therefore examined a worldwide database of plankton RNA sequences collected over the four years Tara Oceans Expeditions global research project. Plankton are aquatic organisms that are small enough to swim against the current.

They are a vital part of ocean food webs and are common hosts for RNA viruses. Our screening ultimately identified more than 44,000 genes that code for the viral protein.

Our next challenge was therefore to determine the evolutionary connections between these genes. The more similar two genes were, the more likely the viruses with those genes were related. Because these sequences had evolved so long ago (maybe anterior to the first cell), genetic markers indicating where new viruses may have split from a common ancestor have been lost over time.

A form of artificial intelligence called machine learning, however, allowed us to systematically organize these sequences and detect differences more objectively than if the task were performed manually.

Swarm plot of the 5 RNA virus phyla
This diagram shows the five known RNA virus phyla automatically organized by our methods. Reprinted with permission from Zayed et al., Science Volume 376:156(2022).

We identified a total of 5,504 new marine RNA viruses and doubled the number of known RNA virus phyla from five to 10. Geographic mapping of these new sequences revealed that two of the new phyla were particularly abundant in large regions oceanic, with regional preferences in temperate regions. and tropical waters (the Taraviricotanamed after the Tara Oceans expeditions) or the Arctic Ocean (the arcticiviricota).

We believe that Taraviricota could be the missing link in the evolution of RNA viruses that researchers have long sought, connecting two different known branches of RNA viruses that have diverged in how they replicate.

World map showing the distribution and abundance of RNA virus phyla.
This map shows the distribution of RNA viruses in the ocean. The size of the wedge is proportional to the average abundance of viruses present in that area, and the color of the wedge indicates the phyla of the virus. Reprinted with permission from Zayed et al., Science Volume 376:156(2022).
why is it important

These new sequences help scientists better understand not only the evolutionary history of RNA viruses, but also the evolution of early life on Earth.

As the COVID-19 pandemic has shown, RNA viruses can cause deadly diseases. But RNA viruses also play a role vital role in ecosystems as they can infect a wide range of organisms, including germs that influence environments and food webs at the chemical level.

Mapping where these RNA viruses live around the world can help clarify how they affect the organisms behind many of the ecological processes that govern our planet. Our study also provides improved tools that can help researchers catalog new viruses as genetic databases expand.

Viruses do more than just cause disease.
What is not yet known

Despite the identification of so many new RNA viruses, it remains difficult to determine which organisms they infect. Researchers are also currently limited to most fragments incomplete RNA virus genomes, in part due to their genetic complexity and technological limitations.

Our next steps would be to determine what types of genes might be missing and how they have changed over time. Finding these genes could help scientists better understand how these viruses work.

[Get The Conversation’s most important coronavirus headlines, weekly in a science newsletter]The conversation

Guillermo Dominguez Huertascientific consultant in microbiology, The Ohio State University; Ahmad ZayedResearcher in Microbiology, The Ohio State University; James WainainaPostdoctoral Researcher in Microbiology, The Ohio State Universityand Matthew Sullivanprofessor of microbiology, The Ohio State University

This article is republished from The conversation under Creative Commons license. Read it original article.


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