Please Pass the Arsenic

from Science/AAAS

A new report in Livescience.com describes a bacteria which can utilize arsenic in place of phosphorus.  Until now science has considered phosphorus as one of the six key elements* serving as the building blocks of life on earth.

Other studies had shown that some microbes are able to chemically process arsenic, that is they can tolerate it without being poisoned.  The new study by NASA's Astrobiology Institute and the U.S. Geological Survey studied a proteobacteria found in the sediments of an alkaline lake that is naturally high in arsenic.
The new finding was the ability of the organism to use arsenic in place of phosphorus in its DNA, building on arsenic rather than just being able to tolerate it.  Scientists gradually reduced the phosphorus available to it, and generation after generation over a year survived without any additional phosphorus.  Studies showed that the microbe substituted arsenic in place of phosphorus in its DNA and got along just fine.

This finding expands the possibilities of life not only in new and unusual places on earth but even the potential existence of life cycles built on different elements elsewhere in the universe.  An expanded discussion is found at Space.com.

* carbon, oxygen, hydrogen, nitrogen and sulfur.