2023-04-19 18:20:26
Strange viruses populating the oceans in abundance, probable distant cousins of the herpes virus, were discovered thanks to data collected by an expedition from the scientific schooner Tara Oceans, according to a study published on Wednesday.
Baptized mirusvirus (“mirus” means “strange” in Latin), these DNA viruses are present on the surface of the seas and oceans of the globe, from the equator to the poles, where they infect plankton.
“These are chimeric viruses, halfway between the giant viruses, also abundant in the oceans where they only infect unicellular organisms, and the herpes virus, which only infects animals, whose humans”, describes biologist Tom Delmont, CNRS researcher, author of the study published in Nature.
The unexpected discovery was made at the Genoscope in Evry (in the Paris region), where the genomes collected by Tara Océans are sequenced.
“We were exploring the tsunami of data from the 2009-2013 expedition, with 300 billion DNA sequences, when we came across an unusual evolutionary signal,” the specialist told AFP. microbial ecology.
Herpes virus BSIP via AFP
This signal was that of a marker gene carried by giant viruses, but also by mirusviruses. “It was as if we had found a treasure on a huge sandy beach with a metal detector,” continues the researcher.
After several years of analysis, scientists from the Tara Oceans consortium and their collaborators were able to characterize this new group of very complex and diverse viruses.
The discovery will make it possible to better understand ocean biodiversity and the importance of viruses in these ecosystems. “We only see viruses as diseases, but their presence in the oceans is natural and beneficial – a bit like our gut microbiota”, according to Tom Delmont.
“By infecting the cells, they destroy them and that puts nutrients back into the ecosystem. This allows a renewal of plankton activity”, develops the biologist.
These viruses also have an amazing evolutionary history because the particular composition of their genome suggests that they are “distant cousins” of herpes.
Herpes viruses are widespread in animals and infect more than half of the world’s human population. But they are completely absent from single-celled marine organisms, and researchers wondered why.
“The enigma might be clarified as follows: thanks to mirusviruses, we imagine what the oceanic ancestor of herpes might have been. This ancestor would have infected unicellular organisms in the oceans millions of years ago, before specializing in the infection of animals,” says the researcher.
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