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, scientists announced today. (Get a genetics overview.)
Dubbed the GFAJ-1 strain, the bacteria can substitute arsenic for phosphorus, one of the six main "building blocks" for most known life. The other key ingredients for life are carbon, hydrogen, oxygen, nitrogen, and calcium.
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.