A recent study reveals that water in our oceans is full of strange RNA viruses that hold various secrets related to the evolution of early life on Earth. 

The coronaviruses that have been wreaking havoc on the world for the last two years are also RNA viruses, but before you get too spooked, that does not mean all RNA viruses are harmful. These microorganisms play an essential role in managing biogeochemical cycles, food cycles, microbial evolution, and overall ecological balance on our planet — and there’s a good chance they can’t infect humans at all.  

A team of international researchers from EMERGE Biology Integration Institute has identified 5,504 new RNA viruses from 35,000 ocean water samples collected during a four-year research expedition project. These new findings have led to the formation of five new virus phyla (taxonomic category below kingdom) and the detection of a gene named RdRp. Interestingly, researchers claim that the RdRp gene has been around since the time life first originated on Earth.

However, this is not the only exciting news about this epic virus discovery.

What’s so intriguing about these new RNA viruses?  

Scientists have studied and categorized thousands of DNA viruses but on the other side, due to their remarkable adaptability, high levels of genetic instability, and ever-changing behavior, the majority of RNA viruses remain unexplored. The researchers at EMERGE believe that their analysis not only reveals more information on virus diversity but also allows us to understand how microbes respond to environmental issues such as climate change. 

“RNA viruses are clearly important in our world, but we usually only study a tiny slice of them – the few hundred that harm humans, plants, and animals. We wanted to systematically study them on a very big scale and explore an environment no one had looked at deeply. Knowing more about virus diversity and abundance in the world’s oceans will help explain marine microbes’ role in ocean adaptation to climate change,” explainedMathew Sullivan, lead author, and professor of microbiology at the Ohio State University.

To study the water samples collected during the Tara Oceans expedition project, researchers employed machine learning along with traditional analysis methods. They analyzed RNA sequences containing the RdRp (RNA-dependent RNA polymerase) gene and eventually found about 44,000 new genes that can lead to the formation of virus protein.

Many of these new genes and viruses didn’t fit in the existing RNA virus classification — in other words, they’re new to science. Therefore, researchers have classified them in not one, but five new phyla: Taraviricota, Pomiviricota, Paraxenoviricota, Wamoviricota, and Arctiviricota. For comparison, animals have 31 phyla, and plants have 14 phyla in total.

“We benchmarked our clusters against established, recognized phylogeny-based taxa, and that is how we found we have more clusters than those that existed,” said Ahmed Zayed, co-first author and scientist at Ohio State and the EMERGE Institute.

The researchers also claim that phyla like Taraviricorta could be “the missing link in the evolution of RNA viruses.” These phyla might reveal connections between some of the existing RNA virus categories that differ in how they multiply.  

The significance of the RdRp gene for RNA viruses

During their analysis, the researchers focused on a gene only found in RNA viruses. This special gene is called RdRp, and it has been evolving and mutating for billion of years. Previously, research published in PeerJ highlighted that mutations in the RdRp gene had been linked to the rise of new coronavirus strains. 

When asked about the importance of RdRp in studying the newly discovered viruses, Zayed commented:

“RdRp is supposed to be one of the most ancient genes – it existed before there was a need for DNA. So we’re not just tracing the origins of viruses, but also tracing the origins of life.”

Writing in The Conversation, the researchers pointed out that their study is still far from finished. They still have to complete the new RNA virus genomes by finding the missing genes from their analysis. Also, there is not enough information available at the moment to know which organisms the new viruses see as their hosts.