Deinococcus radiodurans is listed in the Guinness Book of World Records as "the world's toughest bacterium." And for good reason: The microbe can survive drought conditions, lack of nutrients, and, most important, a thousand times more radiation than a person can. The bacterium, whose name means 'strange berry that withstands radiation,' is the most radiation-resistant organism known.
http://www.genomenewsnetwork.org/articles/07_02/deinococcus.shtml