December 10, 2009

‘Giant’ Virus Discovered, Shares Genes With Other Species

French scientists have identified a giant new virus dwelling inside an amoeba, and that it contains genetic material from other species.

The so-called Marseillevirus is "a completely new viral form," said Didier Raoult, head of infectious and emerging tropical disease research at Aix-Marseille 2 University in France, during an interview with the AFP news agency.

The genome of the 250 nanometer-diameter Marseillevirus includes a sophisticated set of genes that are "very different from the DNA of other virus forms," Raoult said.

This complex repertoire of genes shows that there is genetic exchange between other micro-organisms, such as large viruses and bacteria found in amoeba, he told AFP.

Amoebas are single-cell life forms that can be parasites on either human or animals.  In the current discovery, the amoebas are acting as "a sort of cradle of creation for new viruses and bacteria," Raoult said.

Only a few of these giant viruses, which can be seen through a conventional light microscope, have ever been discovered.  The first one was found by accident in 1993.
However, little is known about them, even today.  In 2008, Raoult led a team that identified viruses that infect other viruses in order to replicate themselves, he said.

The DNA of the giant virus consists of 368,000 basic pairs, the fifth largest ever sequenced, and contains material from plant and animal matter, bacteria and other giant viruses such as the Mimivirus, Raoult 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 specialize", Raoult said, adding that the mechanism was not predicted by Charles Darwin's theory that life originates 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."

Raoult's research was published this week by the Proceedings of National Academy of Sciences.


On the Net: