A bacterium that can not only withstand but thrive on arsenic has been discovered by NASA scientists at the bottom of a Californian volcanic lake. That the bacteria can live on such a toxic substance gives scientists hope that they could discover life in seemingly hostile environments--even on other planets--in forms that they now can't even conceive of, The New York Times' Dennis Overbye reports.

Arsenic is poisonous because it mimics one of the six crucial chemicals we need to live--phosphorus. These bacteria, though, "gradually swapped out atoms of phosphorus in its little body for atoms of arsenic" as the scientists increased the concentration of the poison in the lab, Overbye writes. A scientist who studies the origins of life explains: "Nature only uses a restrictive set of molecules and chemical reactions out of many thousands available. This is our first glimmer that maybe there are other options." Another raved: "It's like if you or I morphed into fully functioning cyborgs after being thrown into a room of electronic scrap with nothing to eat." As Oberbye explains, "until now there has been no substitute for the basic six elements" which sustain life. Now, though, chemical replacements once the province of science fiction seem a little more possible.

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Elspeth Reeve