Viruses: thousands of new species discovered in the oceans

Thanks to a new study of water samples from oceans around the world, researchers have discovered more than 5,000 new species of RNA viruses. The samples were then analyzed for these organisms, a type of virus much less studied than DNA ones.

The number of new species identified by scientists is so high that the researchers proposed doubling the number of taxonomic groups needed to classify RNA viruses, from the five existing phyla to ben 10 phyla.

Until now, few studies and little research have focused on RNA viruses, except for those that cause infectious diseases in humans. But according to Matthew Sullivan, lead author of the study and a professor of microbiology at Ohio State University, the one being studied is just a “small slice” of the many organisms of this type present on Earth.

Searching for RNA viruses in ocean waters around the world

This is why Sullivan and his team focused on studying this type of virus and decided to look for them in an environment that has not been explored from this point of view, such as the oceans. For their research therefore, the scientists analyzed 35,000 water samples taken in 121 different locations scattered throughout all five oceans of the world.

In the water samples, the researchers examined the genetic sequences extracted from plankton, common hosts of RNA viruses, focusing on the sequences belonging to RNA viruses and in particular on an ancient gene called RdRpcommon to all RNA viruses but absent in the others.

In the samples the team identified over 44,000 sequences with this gene. But, because the RdRp gene is billions of years old and has evolved many times over such a large amount of time, it would have been difficult for the researchers to determine the evolutionary relationship between the sequences. That’s why they took advantage of the use of machine learning to organize them and understand the relationships between them.

With their analyzes, the researchers therefore identified a total of 5,500 new species of RNA viruses that fell within the five existing phyla, but which also requested that it be proposed the creation of five new phyla: Taraviricota, Pomiviricota, Paraxenoviricota, Wamoviricota and Arctiviricota.

The importance of this research is not just about our knowledge of this type of virus but, as Ahmed Zayed, co-first author of the study and researcher in microbiology at Ohio State says, “RdRp should be one of the oldest genes: it existed before DNA was needed. So we are not only tracing the origins of viruses, but we are also tracing the origins of life“.

Image by athree23 from Pixabay