According to the scientists, it is an organism never seen before, but it shares genes with herpesviruses and could be a hybrid. Despite this, it could be that its function is necessary.
A team of scientists led by Tom Delmont from the French National Center for Scientific Research (CNRS) has discovered a never-before-identified virus. It is an organism that is thriving on a large scale in all oceans and infecting mainly plankton. Due to their unknown, almost bizarre characteristics, they have been named mirusvirus, since mirus means strange in Latin.
The authors of the study published in Nature point out that mirusviruses belong to a large group of viruses called Duplodnaviria, which includes the herpesviruses. They infect animals and humans, based on shared genes that encode the coat or “particle” that encloses their DNA. But the ones Delmont’s team has discovered also share a staggering number of genes with a group of giant viruses, called Varidnaviria. This suggests that myrusviruses are a rare hybrid between two distant viral lineages.
A chimera in the oceans
“That is why we consider them chimeric – explains Delmont – because they are a mixture of two different groups of viruses: on the one hand, the herpesviruses, based on the genes of the particles, and on the other hand, the giant viruses, based on many more genes.
To find the viruses, the team pored over data from the expedition. Tara Ocean, which collected nearly 35,000 ocean water samples containing viruses, algae and plankton between 2009 and 2013. The researchers then searched for evolutionary clues in millions of genes from microbes. It was by reviewing the data that they detected the new member of the virus family, one that can be found in the surface waters of the polar, temperate, and tropical oceans.
These abundant viruses infect plankton and by invading their cells, it is likely that they help them regulate the activity of microorganisms and thus the flow of carbon and nutrients through the ocean.
“Viruses are a very natural component of plankton on the ocean surface,” Delmont adds. They are going to destroy many, many cells every day and this is going to release nutrients that are going to be used by other cells to be active and healthy. Our finding highlights how little we know about viruses that live in Earth’s oceans.”
The interesting thing about these viruses is that they could not only be related to the nutrients in the sea, they could also be the key to solving the enigmatic origin of the herpes viruses, the scientists say in the study. The genes that code for the protective coat that surrounds the viral DNA are strikingly similar in both groups, suggesting that they are related.
“This means that there is a shared evolutionary history between herpes, which infects only animals, and the myrusviruses that are ubiquitous in the ocean, where they infect single-celled organisms. All this points to a planktonic origin of herpes. These unusual viruses represent a new front for the investigation of microbial life in our oceans, and many more discoveries are awaiting. Working with this data is like scanning a large area of sand with a metal detector, looking for treasure. We found an evolutionary treasure trove,” concludes Delmont.
The objective of the scientists, from now on, is to try to isolate the myrusviruses in order to study them in greater depth and to be able to discover their origin and their possible relationship with other viruses. Thanks to this, it will be possible to “sharpen the aim” when designing drugs and developing therapies to treat herpes… among others.
