Giant viruses aren’t the result of nineteen-fifties Atomic Mutation (now playing in our air-conditioned theater!) but a real infectious agent so unexpected they were only discovered recently. A giant virus was like a tiny elephant – something someone would not only not expect, but actively miss every time they looked because their initial assumptions would screen them out. Now another massive virus has been discovered.
The Marseillevirus (go on, guess where the discovering institute is located) is the fifth largest virus ever found and does things to genetics that make The Fly look like a faithful photocopy. It evolved inside amoebae, which – as well as oozing around the place doing their unicellular thing – act as hosts for an entire ecosystem of infectious agents. Viruses evolve particularly rapidly, stealing genes from whatever host (or even other viruses) they can get their proteins on, experimenting with millions of variations to find which ones work.
Some viruses become so large that other viruses can infect them, tiny super-specialized parasites piggy-backing their genetic code on their huge cousins. Others simply fail, their patchwork genomes not up to the challenges of the environment. The Marseillevirus has stolen ten percent of its chromosomes from bacteria it once infected, and anther five percent from the amoebic host of the party. It’s even infiltrated other giant viruses, taking parts of the mimivirus for its own purposes.
Don’t worry about any mass-media scare stories: this thing is no threat to us and there isn’t a shred of evidence to suggest otherwise. Not that the latter necessarily affects the former.
Scientists in France have isolated a new giant virus that lurks inside amoeba and whose gene pool includes genetic material from other species.
// The virus “is a completely new viral form,” said Didier Raoult, head of infectious and emerging tropical disease research at Aix-Marseille 2 University in France.
The genome of the so-called Marseillevirus encompasses a complex repertoire of genes that are “very different from the DNA of other virus forms,” and shows that there is genetic exchange between other micro-organisms such a giant viruses and bacteria found in amoeba, he told AFP in an interview.
Amoeba, single-cell life forms that can be parasites on either human or animals, are acting as “a sort of cradle of creation for new viruses and bacteria,” Raoult said, whose research was also published this week by the Proceedings of National Academy of Sciences.
Only a small number of so-called giant viruses have been discovered, the first in 1993 by accident. Unlike classic viruses, they can been viewed through a conventional light microscope. …
With a genome of 368,000 basic pairs, Marseillevirus is the fifth biggest virus ever sequenced and has a diametre of 250 nanometres (around 250 millionth of a millimetre, according the a report by Raoult’s for the French National Centre for Scientific Research (CNRS).
The DNA of the giant virus contains material from different sources including plant and animal matter, bacteria and other giant viruses such as the Mimivirus, the report said. …