THE world鈥檚 largest virus has also turned out to be the strangest ever discovered. It blurs the boundary between viruses and cellular organisms.
Mimivirus was discovered last year in amoebas in a cooling tower in the UK by a research team from France (快猫短视频, 5 April 2003, p 18). It has the characteristic coat of a virus but, at 400 nanometres across, the organism is larger than some bacteria. Now the same researchers have sequenced the virus鈥檚 genome and uncovered more surprises.
The conventional view is that viruses are parasites that are totally dependent on the cells they invade. According to most definitions of life, they are not even living. But the mimivirus might just be alive: its genome suggests it carries out functions never before seen in viruses, such as making its own RNA and proteins, repairing its DNA and producing various chemicals.
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What鈥檚 more, an analysis of its genome suggests the virus is more closely related to eukaryotes (organisms with complex cells such as plants and us) than to bacteria and other viruses.
鈥淭his guy is definitely some kind of living fossil,鈥� says team member Jean-Michel Claverie of the Institute of Structural Biology and Microbiology in Marseille. He believes that there could be many more mimivirus-like beasts out there. 鈥淚 would predict that our world record is not going to last very long.鈥�