Desalinization, the microbial way.

Respiration -- the final step in the process by which cells break down their food sources -- releases high-energy electrons. In most cells, it also initiates the pumping of protons across a cell membrane. But Dale A. Webster, a microbiologist at the Illinois Institute of Technology, noticed that an unusual bacterium instead pumps sodium ions across its outer cell membrane during respiration. And that gave him the idea of embedding the agent responsible for the pumping in a synthetic membrane separating who tanks of seawater. An electrical current passing into the membrane should drive most of the sodium ions from one tank into the other -- desalinating the water in the first tank.

Webster recently identified the bacterium's sodium pump as a protein pigment known as cytochrone-o. He says it appears that the electrons released during respiration energize the pigment, catalyzing its sodium pumping activity. Because a commercial system would probably require the development of a simpler, functionally equivalent variation of cytochrome-0, Webster is trying to tease out precisely how the original functions. His calculations indicate that "if you can get about one electron to transfer one sodium from one side [of the membrane] to the other, that's cheaper than any other desalination process" -- perhaps by a factor of 10 to 100, he says.