Earth's Extreme Life Knows No Bounds

While Arsenic was not their first choice for a meal, the bactiera that Dr. Felisa Wolfe-Simon collected from the mud in Mono Lake not only managed to survive when cultured only on the toxic ingredient, they used the chemical as a cellular building block. In their natural environment these bacteria normally chow down on phosphorus salts.

SEE ALSO: New Life Form Lives on Arsenic

For most organisms the similarity between phosphorus and arsenic leads to cellular death: the body mistakenly accepts arsenic, but then the chemical doesn't live up to the phosphorus standards and the biochemical cycle shuts down.

Tune into the Science Channel Saturday at 8pm ET/PT to watch "How Did We Get Here?" in the "Through the Wormhole" series.

In the last decade, astrobiologists working at Mono Lake and other arsenic-laden environments have identified a growing list of bugs that can use arsenic as an energy source, but until now none had demonstrated the ability to live off the stuff. In the microbial world, this discovery is akin to finding a fish that can live happily in a bottle of Diet Coke.

SEE ALSO: Arsenic Fueling Calif. Lake Bacteria

The test pushes the boundaries for what life is capable of on Earth and how to define it. But it is perhaps not unexpected. Astrobiologists know there is much about life we don't know or understand, and that's what makes each new way of thinking about life so exciting.

The surprise discovery of ecosystems at hydrothermal vents in 1977, led to the search for extreme life across the planet. And the conclusion is life on Earth, anyway, is everywhere.

Biologists have "found life in hot black smokers at bottom of the sea, life in geysers, blind fish in caves, bacteria that live in the cooling ponds of nuclear reactors that have self-repairing DNA; you have all of these extremophiles but no one knows how life formed," says Malcolm Fridlund, astrophysicist with the European Space Agency in Moordwijk, Holland. "We don’t know if life formed under tough conditions or under benign conditions and then evolved to fill-in every niche."

These bacteria demonstrate that life is adaptable, and does not need to rely solely on the six elements that are traditionally considered necessary for life: carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. If we can add arsenic to that list anything is possible.

"We know that extremophiles can survive extreme heat, cold, vacuum and radiation. Now we know of an organism that metabolizes arsenic to live, the same toxin that damages life as we know it on a genetic level. The horizons for extraterrestrial-hunting missions have widened once again," says our in-house expert Ian O'Neill.

Image: (Top) Dr. Felisa Wolfe-Simon of the NASA Astrobiology Institute and U.S. Geological Survey pulls up a core of mud from the bottom of Mono Lake in California. (bottom) Dr. Felisa Wolfe-Simon uses samples as starters for microbial cultures that she will grow in high arsenic conditions when they would normally live off phosphorus. © 2010 Henry Bortman