Scientists have discovered the first organism able to substitute one of the six chemical elements crucial to life.
The bacterium, found in a lake in California, replaces phosphorus with the usually poisonous element arsenic and builds it into its DNA.
The discovery gives weight to the idea that life on other planets may have a chemical make-up very different from on Earth. It may also mean that life arose more than once on Earth, each time with a different set of essential chemical ingredients.
