Disease experts discover giant virus in amoeba

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 "very different from the DNA of other virus forms", and shows there is genetic exchange between other micro-organisms such a giant viruses and bacteria found in amoeba, he said.

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", Dr Raoult said. The research was 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.

In 2008 a team led by Dr Raoult even found viruses that infect other viruses to replicate themselves, he said.

With a genome of 368,000 basic pairs, Marseillevirus is the fifth biggest virus ever sequenced and has a diameter of 250 nanometers (around 250 millionth of a millimetre, according the a to the report.

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," Dr Raoult said.

He said the mechanisms were 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."

- INDEPENDENT