A team of researchers working out of the Centre National de la Recherche Scientifique in France has discovered a new giant virus living in an amoeba found in an eye patient's contact lens fluid. They also found a new kind of virophage inside the virus which itself was harboring a previously unknown class of genetic parasite they've named transpovirons.
The researchers named the giant virus Lentille and found that it belongs to a group of giant viruses known as Mimiviridae. They named the virophage – a virus that infects other viruses – living inside the Lentille virus, Sputnik 2, (Russian for "fellow traveler"). Inside of the virophage they found fragments of DNA that didn't belong to the amoeba, the giant virus or the virophage, indicating that it was class of unknown genetic parasite that they've named transpovirons.
Sputnik 2 is just the fourth known virophage and is unique in that it can insert its DNA into its host genome, which might explain why the genomes of different giant viruses are so similar. In looking closer at the virophage Sputnik 2, the team found fragments of DNA inside of it that didn't belong to any of the hosts; strands that outnumbered the giant viruses DNA by up to 14 times. Because there was no record of such fragments being observed before, the team gave them a name: transpovirons. As the name implies, the fragments were found able to jump in and out of host DNA in similar fashion to transposons.
The researchers believe transpovirons need giant viruses to replicate and are exceptionally good at reproducing and also appear to ride around in virophages. And because of the large variety of DNA found in them, the team believes they get their material from many different sources, similar in that respect to virophages, which other researchers have found contain the genomes of other giant viruses. Because only a small amount of work has been focused on giant viruses, the team believes it's likely that other virophages and transposons will soon be discovered as more resources are dedicated to their study.