Was our oldest ancestor a proton-powered rock?

PETER MITCHELL ... won a Nobel prize in 1978. Even today, though, most biologists have yet to grasp the full implications of his revolutionary ideas - especially for the origin of life.

"Mitchell's ideas were about how cells are organised in space, and cellular energy generation is a feature of that," says geochemist Mike Russell of NASA's Jet Propulsion Laboratory in Pasadena, California. "The problem is that most ideas on the origin of life lack both spatial organisation and a supply of energy to drive replication or growth."

A few researchers, including Russell, have been rethinking the origin of life in the light of Mitchell's ideas. They think the most counter-intuitive trait of life is one of the best clues to its origin. As a result, they have come up with a radically different picture of what the earliest life was like and where it evolved. It's a picture for which there is growing evidence.

... proton gradients are often harnessed directly, rather than being used to make ATP. They drive the rotation of the bacterial flagellum, as well as the active transport of numerous substances in and out of cells. So proton power is central to energy generation, movement and maintaining the internal environment - some of the most basic features of life.

This suggests that proton power is no late innovation but evolved early in the history of life, an idea supported by the tree of life. The first branch in the tree is between the two great groups of simple cells, bacteria and archaea. Both of these groups have proton pumps and both generate ATP from proton currents, using a similar protein. The obvious explanation is that both inherited this machinery from a common ancestor - the progenitor of all life on Earth. ...

via Was our oldest ancestor a proton-powered rock? - life - 19 October 2009 - New Scientist.