Arsenic metabolizing bacterium

A new species of bacteria found in California's Mono Lake is the first known life-form that uses arsenic to make its DNA and proteins.

Arsenic is toxic to most known organisms, in part because it can mimic the chemical properties of phosphorus, allowing the poison to disrupt cellular activity.

The newfound bacteria not only tolerates high concentrations of arsenic, it actually incorporates the toxic elementl into its cells, to substitute phosphorous.

Researchers took samples of bacteria from California's Mono Lake, a briny, arsenic-rich lake in a volcanic valley southeast of Yosemite National Park. They cultured Mono Lake bacteria in Petri dishes, gradually increasing the amount of arsenic while reducing phosphorus. Chemical analyses with radioactive tracers showed that the GFAJ-1 strain bacteria was in fact using arsenic in its metabolism.

The GFAJ-1 strain might be called the most unusual of the extremophiles, bacteria that thrive under exceptionally harsh conditions, such as high heat, high salt, and low oxygen.