Giants amongst viruses


Last month, evolutionary biologists Jean-Michel Claverie and Chantal Abergel of Aix-Marseille University, France, revealed the largest viruses ever found: the Pandoraviruses.

The dimensions of the viruses are, at around 1 micrometre long, closer to that of bacteria than they are their fellow viruses. At this size they are visible under a light microscope as a small black dot, something that cannot be said for most viruses. It has since emerged that these viruses had been found before, but no one had considered they could be viruses, simply due to their size.

Their genomes are equally huge, reaching up to 2.5 million bases. But most interestingly of all, only 7% of this genome has been seen before. To put that into perspective, we humans are said to share 99% of our genes with chimpanzees, 82% with a platypus and 40% with a banana; clearly then, these viruses are like nothing that has been found before. In fact, they share so little with those already known to us that they were initially dubbed NLFs, meaning ‘New Life Form’.

This huge number of previously unknown genes is said by some to point to a new division in the tree of life, a so-called ‘fourth domain’ to sit alongside the existing domains of Eukaryotes (animals, plants etc), Bacteria and Archaea. The potential discoveries that may be made when scientists start poking around in the genome of these Pandoraviruses are what gives them their name: some liken it to opening Pandora’s Box. According to Dr Abergel, “the genes of these new viruses might point to alternative metabolic pathways that might revolutionise the biotech and pharmaceutical industry.”

“We still have more crazy things in store that we expect to be able to publish next year”.