Strange herpes virus found to be thriving in the world's oceans

Upon investigation, it was found that mirusviruses are members of a virus family known as Duplodnaviria. This category includes herpesviruses, which are known to infect both animals and humans.

They did, however, notice that these viruses share a large number of genes with another group known as Varidnaviria. This suggests that mirusviruses are a hybrid of the two previously aforementioned virus groups. 

"They seem to be an extremely unusual group of viruses. This is why we consider them as being chimeric, because they are a mix of two different groups of viruses — on one side the herpesviruses, based on the particle genes, and on the other side the giant viruses, based on many more genes,” Tom Delmont, a researcher at the CNRS, told Live Science.

The viruses were discovered to be double-stranded DNA viruses during the lab examination. These unusual viruses are thought to infect plankton, which are tiny microbes that swim across oceans based on currents.

It is possible that the newly discovered virus can spread throughout the world's oceans by infecting plankton.

By infecting the cells of plankton, they may help regulate the activity of microorganisms, causing carbon and nutrients to flow through the ocean.

This study is based on a wealth of data obtained from the Tara Ocean expedition, one of the largest projects to investigate plankton biodiversity. 

Between 2009 and 2013, this project collected up to 35,000 ocean water samples containing viruses, algae, and plankton. In the lab, these samples were thoroughly examined to look for evolutionary clues of viruses or to discover new ones.

This study holds the potential to decode the origins of herpes viruses. The team will also isolate this newfound virus in order to better understand its origins and other characteristics. Scientists believe that there are more unusual microbes waiting to be discovered in the vast and unexplored territories of the world's oceans. 

The full study was published in Nature on April, 19 and can be found here.

Study abstract:

DNA viruses have a major influence on the ecology and evolution of cellular organisms, but their overall diversity and evolutionary trajectories remain elusive. Here we carried out a phylogeny-guided genome-resolved metagenomic survey of the sunlit oceans and discovered plankton-infecting relatives of herpesviruses that form a putative new phylum dubbed Mirusviricota. The virion morphogenesis module of this large monophyletic clade is typical of viruses from the realm Duplodnaviria, with multiple components strongly indicating a common ancestry with animal-infecting Herpesvirales. Yet, a substantial fraction of mirusvirus genes, including hallmark transcription machinery genes missing in herpesviruses, are closely related homologues of giant eukaryotic DNA viruses from another viral realm, Varidnaviria. These remarkable chimaeric attributes connecting Mirusviricota to herpesviruses and giant eukaryotic viruses are supported by more than 100 environmental mirusvirus genomes, including a near-complete contiguous genome of 432 kilobases. Moreover, mirusviruses are among the most abundant and active eukaryotic viruses characterized in the sunlit oceans, encoding a diverse array of functions used during the infection of microbial eukaryotes from pole to pole. The prevalence, functional activity, diversification and atypical chimaeric attributes of mirusviruses point to a lasting role of Mirusviricota in the ecology of marine ecosystems and in the evolution of eukaryotic DNA viruses.