Radiation-resistant bacteria encompass eight species of bacteria in a genus known as Deinococcus. The prototype species is Deinococcus radiodurans. This and the other species are capable of not only survival but of growth in the presence of radiation that is lethal to all other known forms of life.

Radiation is measured in units called rads. An instantaneous dose of 500 to 1000 rads of gamma radiation is lethal to a human. However, Deinococcus radiodurans is unaffected by exposure to up to 3 million rads of gamma radiation. Indeed, the bacterium, whose name translates to "strange berry that withstands radiation," holds a place in The Guinness Book of World Records as "the world's toughest bacterium."

The bacterium was first isolated in the 1950s from tins of meat that had spoiled in spite of being irradiated with a dose that was thought to be sterilizing. The classification of the bacterium as...