A new chapter in the understanding of viruses in marine ecosystems opens with the discovery of 5,500 new species.
- An analysis of the genetic material contained in the oceans has revealed the presence of several thousand previously unknown RNA viruses
- These viruses have been identified in the World Ocean from water samples taken during the Tara Ocean mission
A veritable floating laboratory, the schooner Tara Oceanwho has been traveling the oceans for more than ten years to better understand marine biologybrought back tens of thousands of samples of water from all the world’s oceans.
It was by studying these samples that the researchers discovered the presence of several thousand previously unknown RNA viruses.
These RNA viruses – popularized by the Covid-19 pandemic, differ from classic DNA viruses because they evolve much faster. They cause illnesses ranging from the common cold to Covid-19 or Ebola, but they also infect our environment, plants or animals. The water samples collected by Tara Ocean constitute a veritable database plankton RNA sequences, which is a common host for RNA viruses.
Their presence remains relatively unstudied because RNA viruses lack the barcode genetics – unique short stretches of DNA – that distinguish one species from another.
Double the number of virus biological groups
This incredible discovery comes to double the number of biological groups of viruses thought to exist, specify the researchers of the ohio state university (United States) who identified them. The trick used by microbiologists: working on a protein shared by all RNA viruses. Or more exactly on the gene RdRp who encodes it. Because this gene has small differences that can help distinguish one type of virus from another. And then it doesn’t show up in other viruses or cells.
missing link
The researchers differentiated 5,504 new RNA viruses, increasing the number of known virus biological groups from five to ten. They even think they have found Taraviricota – a group present in all the oceans -, the missing link in the evolution of RNA viruses that scientists have long sought.
This work is not only important because RNA viruses can be deadly to humans, they are also important because they shed light on the evolution of life on Earth. The RdRp gene might be one of the oldest genes in the world. It existed even before life needed DNA.
Central role in ecosystems
RNA viruses also play a central role in ecosystems: by infecting all kinds of organisms, they influence environments and food webs at the chemical level – a food web is the set of feeding relationships between species within an ecosystem, through which energy and matter circulate.
They could thus have a role to play on the way the oceans adapt to global warming and of which they absorb and store about half of the carbon that our activities emit into the atmosphere.
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