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New Giant Viruses

Two giant, amoeba-killing viruses have been discovered that "hints at unknown parts of the tree of life," according to Nature.

Investigators from Aix-Marseille University of France found one of the viruses, which are about 1 micrometer long and about half that wide, off the coast of Chile, and later snagged another in a sample taken from a pond in Australia.

Only by comparing the two did the team realize these were viruses, which are larger than many bacteria, and they have now named them Pandoraviruses, Science's Ed Yong writes.

They also think that these viruses may represent "unknown parts of the tree of life," as only 7 percent of their genes match those found in existing databases.

“What the hell is going on with the other genes?” asks Aix-Marseille investigator Jean-Michel Claverie, adding that the find "opens a Pandora’s box."

Whichever parts of the tree of life they will be etched into, the Pandoraviruses are widespread, as another was found inside an amoeba living in the contact lens of a woman in Germany who had keratitis, Yong writes.

“Reading this stunning article, I recognized that both P. salinus and P. dulcis are almost identical to what we described a few years ago,” says Rolf Michel, a parasitologist from the Central Institute of the Bundeswehr Medical Service, who found the German specimen in 2008. “We had no idea that those giant organisms could be viruses at all!"

The investigators found that the Pandoraviruses have a viral life cycle, contain core genes that are common to giant viruses, and observed them emptying proteins into the cells of amoeba and splitting those host cells open.

Now, the researchers plan to characterize the unknown genes and proteins the pandoraviruses encode and find out more about their evolutionary history, particularly to find out if they evolved from cells and how they may factor into the broader evolutionary picture.