Over 5,000 new virus species have been discovered in ocean water samples collected from all over the world, a new study found.
Researchers from Ohio State University in the US analyzed water samples using a combination of machine-learning analyses with traditional evolutionary trees to identify the RNA viruses.
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RNA viruses have ribonucleic acid (RNA) as its genetic material and are often single or double stranded. Such viruses are the most common cause of emerging diseases in humans due to their high mutation rate, according to Science Direct.
Some well-known RNA viruses include Ebola, the coronavirus and influenza.
“There’s so much new diversity here – and an entire phylum, the Taraviricota, were found all over the oceans, which suggests they’re ecologically important,” said lead author Matthew Sullivan, professor of microbiology at Ohio State University.
“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, and we got lucky because virtually every species was new, and many were really new,” he added.
The study entitled ‘Cryptic and abundant marine viruses at the evolutionary origins of Earth’s RNA virome’ and published in the journal Science on Thursday, involved the analysis of 35,000 water samples taken from 121 locations in all five of the world’s oceans: the Pacific, Atlantic, India, Southern, and Arctic Oceans.
The researchers – who are also part of the Tara Oceans Consortium, a global project to analyze the impact of climate change on the world’s oceans – examined genetic sequences extracted from small aquatic organisms known as plankton.
Plankton are common hosts for RNA viruses, the researchers said.
They also examined sequences belonging to RNA viruses by looking for an ancient gene RdRp, a gene found in all RNA viruses. The scientists identified over 44,000 sequences with this gene.
“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 co-first author Ahmed Zayed, a research scientist in microbiology at the university and a research lead in the EMERGE Institute.
Zayed said the extent of new data on the RdRp gene’s divergence over time leads to a better understanding about how early life may have evolved on the planet.
“RdRp is supposed to be one of the most ancient genes – it existed before there was a need for DNA,” he added. “So we’re not just tracing the origins of viruses, but also tracing the origins of life.”
Overall, they identified around 5,500 new RNA virus species falling into the five existing phyla and five new proposed phyla which they named Taraviricota, Pomiviricota, Paraxenoviricota, Wamoviricota and Arctiviricota.
Phyla are a group of related living animals or plants that rank above the class and below the kingdom and above class, according to the Merriam Webster Dictionary.
“We had to benchmark the known to study the unknown,” said Sullivan, also a professor of civil, environmental and geodetic engineering, founding director of Ohio State’s Center of Microbiome Science and a leadership team member in the EMERGE Biology Integration Institute.
“We’ve created a computationally reproducible way to align those sequences to where we can be more confident that we are aligning positions that accurately reflect evolution.”
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