Published on nature news, by Virginia Gewin, March 28, 2011.
First of the parasitic parasites to be discovered in a natural environment points to hidden diversity.
A genomic survey of the microbial life in an Antarctic lake has revealed a new virophage — a virus that attacks viruses. The discovery suggests that these life forms are more common, and have a larger role in the environment, than was once thought.
An Australian research team found the virophage while surveying the extremely salty Organic Lake in eastern Antarctica. While sequencing the collective genome of microbes living in the surface waters, they discovered the virus, which they dubbed the Organic Lake Virophage (OLV) … //
Another virophage described this month has similar ecological effects. The marine Mavirus attacks the giant Cafeteria roenbergensis virus, which preys on Cafeteria roenbergensis, one of the world’s most widespread species of zooplankton2.
“The Mavirus is able to rescue the infected zooplankton — which, in a way, confers immunity from infection,” says Curtis Suttle, a marine microbiologist at the University of British Columbia in Vancouver, Canada, and leader of the team that discovered the Mavirus.
“We unknowingly had Mavirus in culture with our Cafeteria system since the early 1990s,” says Suttle. But the virophage was not identified until the Cafeteria genome was sequenced.
The Mavirus genome is similar to DNA sequences called eukaryotic transposons, which insert themselves within the genomes of multicellular organisms such as plants and animals. These ‘jumping genes’ may be descended from a virophage, says Suttle. “One can imagine evolutionary pressure for hosts to somehow cultivate virophages to protect themselves from infection by giant viruses,” he says.
French Sputnik: … (full text).