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.

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.

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.

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 extremeophiles but no one knows how life formed," says Malcolm Fridlund, astrophysicist with the European Space Agencey in Moordwijk, Holland. "We don’t know if life formed under tough conditions or under benign conidtions 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 consider necessary for life: carbon, hydrogen, nitrogen, oxygen, sulfur, and phosphorus. If we can add arsenic to that list anything is possible.

Read more at Discovery News