Microscopic representation of an RNA-type virus

Over 5,000 RNA viruses found in the oceans

The unknown has always been a source of undying curiosity for humans. But what is going on above our heads, and below our feet? In this sense, the seabed is an endless well of theories, wonder and mythology about the unexplored areas.

After researching the waters of the world's oceans and more specifically the plankton collected by the Tara Oceans, les chercheurs ont ramené avec eux, non pas de l’or, mais… 5 500 virus inconnus.

5,500 viruses: a puzzling discovery?

Scientists have returned from an expedition with a large quantity of water from the world's oceans. Among this water, they found water and plankton, plankton and viruses, but above all a significant number of viruses: more than 5 500. They published their research in the journal Science, in the article Cryptic and abundant marine viruses at the evolutionary origins of Earth's RNA virome.

The research was based on the observation that "while DNA viruses are known to be abundant, diverse and generally key players in the ecosystem, RNA viruses are insufficiently studied outside of disease findings. The primary objective of the research was therefore to study these RNA viruses in greater depth, by sampling the waters of the world's oceans, outside of studies via diseases.

The research was successful, as the catalogue of RNA viruses and their classification has been extendedThis was achieved by analysing the genetic material in the water samples. More than 5 000 viruses were discovered, mainly RNA viruses that were previously unknown. Precisely, 5,504 new RNA viruses which were revealed through the analysis of the samples, and artificial intelligence to enable 3D modelling of the sequence structures of the genetic material and thus its analysis. This colossal discovery was also made possible by the sheer scale of the research, with over 30,000 samples from more than 100 different regions.

Avydyu | DNA and RNA viruses: what is the difference?

What is an RNA virus?

Research has reached its goal: RNA viruses. But what is an RNA virus?

These viruses are different from DNA viruseswhich can be distinguished by their genetic 'barcode'. This barcode is not present in RNA viruses, which makes them very little studied overall, except for the diseases they cause, from the common cold to Ebola. Without a barcode, RNA viruses use RNA, a nucleic acid, as genetic material.

In short, the genome, i.e. the genetic information of an organism present in all its cells, is different in its material support which is DNA for DNA viruses and RNA for RNA viruses. From this, DNA viruses replicate in the nucleus, but RNA viruses replicate in the cytoplasm. In addition, RNA viruses are, for the most part, more mutagenic than DNA viruses.

5,500 viruses: an interesting discovery? 

At first glance, the fact that more than 5,000 viruses have been discovered may be a cause for concern. But if you look at it scientifically, it is a very interesting discovery.

On the one hand, it is interesting in terms of the research objective: to better understand RNA viruses. As the article states, "these efforts provide fundamental knowledge and essential for the integration of RNA viruses into ecological and epidemiological models. In addition to their understanding in diseases, this research has thus broadened both the catalogue of known RNA viruses, but also their understanding in aspects that were unknown, namely their roles in ecosystems, in living things today and across time.

On the other hand, it has opened up enormous opportunities in line with these new understandings. In particular, it is a discovery around a gap that the scientific world has long wanted to fill in the quest to understand the evolution of RNA viruses throughout history. With this research, they believe they have finally found this missing link in RNA virus evolution, as well as "new phyla that dominate the oceans and could infect mitochondria," where all of this "helps to reshape the contours of RNA virus evolutionary history." In addition, it is also about linking each of its new viruses with the organisms they infect and the diseases they causeThis is unknown today.

A discovery that is therefore both disconcerting and hopeful.