New giant virus discovered

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.

Cradle of creation

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.

Even now little is known about them but in 2008, a team led by Raoult even found viruses that infect other viruses so as to replicate themselves, he said.

250 millionth of a millimeter

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.

"There is a mechanism of permanent creation going on in amoeba producing a new repertoire of viruses and predisposing giant viruses to become pathogens once they specialise", Raoult said.

He said the mechanism was not foreseen by Charles Darwin's theory that life comes from a common ancestor.

"The idea of a common ancestor makes no sense in the light of viruses," he said. "That was Darwin's idea, but he was clearly wrong." - (Sapa/AFP, December 2009)