Like it or not at some point in your life you have been host to a virus. These tiny inert particles become living only when they enter our bodies, often causing the flu or just a common cold. These cunning creatures dock onto host cells and inject their genome inside, making it a miniature virus factory. The cell eventually bursts, releasing many more viruses in the process. So far we have discovered thousands of different types. French scientists have now reported a new family of viruses, which have a genome twice as large as we thought possible, and show extremely little resemblance to any microorganism we know 1.
This proposed new family have been named ‘Pandoraviruses’ as they may have surprises in store! They are not infections to humans, but parasitise amoeba. They describe two family members; the first was found lurking 10 meters under the Tunquen River in Chile and the other in a pond in Melbourne. What is most striking about these viruses is not only that they are physically the largest virus discovered to date, but also that their genomes are twice as large as any other known virus.
To expose the secrets of this mysterious family, scientists sequenced the genomes of the new family members. This revealed that these viruses may contain genes we have not yet encountered. In fact, more than 93% of Pandoravirus genes resemble nothing known. We can’t track them to any of the cellular families we know, suggesting they may belong to a new domain of life. This discovery may require us to rethink the tree of life in order to accommodate them.
