Researchers have brought a giant virus dating back to the days of the mammoths and the last Neandertals back to life. Others had resurrected ancient viruses before by reconstructing their genomes from old DNA, but this may be the first time that the ancient virus itself has proved viable: The researchers simply dissolved 32,000-year-old frozen soil from Siberia and mixed in amoebas, known hosts for giant viruses. Researchers studying the microbiology of permafrost collected that soil by drilling into exposed layers of a cliff face. That a giant virus was still able to kill the amoebas after all this time suggests other pathogens can last thousands of years in frozen soil and, as the planet warms, may be let loose. Unlike most viruses, giant viruses are big enough to be seen with a light microscope. Indeed, the first one discovered was initially thought to be a bacterium, with comparable amounts of DNA. Since then, about 10 more have been found, including ones with more DNA than some bacteria, most infecting amoebas only. This new virus, called Pithovirus sibericum, has some characteristics of other giant viruses, but represents a third group of these unusual life forms. It’s the biggest to date, but has about half the DNA of others, researchers report online today in the Proceedings of the National Academy of Sciences. The soil studied was taken from 30 meters below the surface, and the researchers have samples dating back millions of years that they plan to test as well.

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