Arsenic, microbe raise possibilities for life

FRIDAY, DEC. 3, 2010

LOS ANGELES – A team of scientists revealed Thursday that they had found a remarkable quality in a bacterium growing quietly in California’s Mono Lake – it is the only known life form able to subsist on the deadly element arsenic. The organism even uses arsenic to build the backbone of its DNA.

To researchers searching for life elsewhere in the universe, the discovery qualified as a heaven-sent event.

“I find this result delightful,” said Pamela Conrad, an astrobiologist at NASA’s Goddard Space Flight Center in Greenbelt, Md., who wasn’t involved in the research.

The organism’s existence suggests life on Earth has an unappreciated flexibility, experts said, and could have evolved from a wider array of building blocks than previously thought – not only here, but elsewhere in the universe.

Perhaps no one was more surprised than Felisa Wolfe-Simon, the biochemist who identified the creature.

“The mere fact that an organism can grow with this much arsenic, that’s outrageous,” said Wolfe-Simon, a NASA research fellow based at the U.S. Geological Survey in Menlo Park, Calif.

All life on Earth relies on six principal elements – carbon, hydrogen, nitrogen, oxygen, sulfur and phosphorus.

Wolfe-Simon had theorized arsenic might be able to stand in for phosphorus because it is located directly below phosphorus on the periodic table of elements and behaves similarly.

Researchers said the finding, published online Thursday in the journal Science, has forced them to reconsider what they ought to be looking for as they hunt for signs of life beyond Earth.


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