Scientists may argue whether or not a virus is really alive, but no one denies that they’re cellular parasites – hijacking a cell’s reproductive machinery in order to make new viruses. But a study in this week’s issue of Nature adds a new twist: a virus that’s a virus of a virus.
In this little bit of natural history, the virus playing host is the largest one known: mimivirus is about the same size as some bacteria. Still small, to be sure, but viruses are typically even smaller. The infecting virus, called Sputnik, is more typically sized, about 50 nanometers long. Both viruses can be found in association with the amoeba Acanthamoeba polyphaga, but Sputnik doesn’t replicate itself without mimivirus. When mimivirus builds a viral factory inside inside A. polyphaga, Sputnik jumps in and uses it to build more of itself. Sputnik makes new viruses faster than mimivirus can, and when mimivirus is infected with Sputnik it tends to build abnormal protein coats for its own descendants. But what’s bad for mimivirus seems to be good for the amoeba – typically, mimivirus makes its host cell explode to let the new viruses escape, but when Sputnik is present it reduces amoeba lysis threefold.
Source (and Image): La Schola, B. et al. 2008. The virophage as a unique parasite of the giant mimivirus. Nature 455: 100-104.
wow i am just taking acurse in virology and ican't stop be amazed by them...
Posted by: yonatan | December 30, 2008 at 12:22 PM