A completely new type of virus has been found that lives on the sunny surface of the seas and oceans. Named mirusviruses, inspired by the Latin word “mirus” meaning wonderful or strange, these new entities seem to be related to both giant viruses and herpes viruses. The discovery may therefore help illuminate the evolutionary history of herpes viruses.
Scientists have detailed the discovery of mirusviruses in a new study and stated that they belong to a group of viruses called Duplodnaviria. This is known as a large type of double-stranded DNA virus, which includes herpes viruses such as the herpes simplex virus.
Mirusviruses are not interested in humans and seem to tend to infect only single-celled plankton. But this suggests that the ancestors of herpes viruses once infected single-celled organisms in the sea. Considering that the plane has managed to affect half of humanity since then, it can be said that they have made a very impressive journey.
Although their evolutionary inheritance is linked to herpes viruses, many of the mirusvirus genes are similar to those of giant viruses (really large viruses, literally). The researchers say this never-before-seen group of viruses is quite unique.
The study authors conclude, “Mirusviruses diverge substantially from all other previously characterized DNA virus groups,” and add: “The discovery of Mirusviricota has yet to reveal the full ecological and evolutionary complexity of even the most abundant double-stranded DNA viruses in important ecosystems such as the surface of our oceans and seas. It reminds us that we don’t fully understand it.”
The new viruses were found by scanning data collected by the Tara Ocean expedition. This project collected more than 35,000 samples of viruses, algae and plankton from more than 200 different locations around the world.
By sequencing the genetic material of myrusviruses, scientists have had plenty of data to explore in detail and many opportunities to discover new species.
“In 2019, our research team observed an unusual evolutionary signal in the enormous amount of sequencing data provided by the Tara Oceans project,” said Tom Delmont, a microbial ecologist at the French National Center for Scientific Research and study author. By tracking this signal, we discovered and characterized a large group of DNA viruses: mirusviruses. “The publication of this discovery in Nature marks the beginning of a new adventure and a gateway for the scientific community to detect and study myrusviruses in any number of ecosystems.”
“Tara Oceans has changed our understanding of plankton ecology,” said Morgan Gaïa, first author of the study. Our work proves that this incredible expedition also provides answers to fundamental evolutionary questions. There is much to discover and understand about mirusviruses. “They have to be planted yet, there are no images of their viral particles and we haven’t been able to study them anywhere else but the oceans yet,” he added.
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