June 23, 2005— Dim light released by deep sea vents may act like underwater sunlight to energize photosynthetic, or light-loving, organisms, according to scientists who just discovered a bacteria basking in the geothermal radiation of a vent plume.

The bacteria, found one and a half miles below the surface of the Pacific Ocean, suggest that all photosynthesizing organisms, such as plants and trees, might be descended from plume dwellers that lived approximately 3 billion years ago.

The find, outlined in this week's Proceedings of the National Academy of Sciences, also indicates life could exist on planets with little or no sunlight, including planets in galaxies beyond Earth's solar system.

"(Our findings) raise the possibility that life on other, 'dark' worlds may be more diverse than previously thought," said J. Thomas Beatty, who led the study.

Beatty, a professor of microbiology and immunology at the University of British Columbia, and colleagues obtained a water sample from a plume of an East Pacific Rise black smoker.

Smokers and other vents, which look like underwater chimneys, form from cracks in new oceanic crust made from molten rock bubbling out of Earth's interior.

The sample yielded green sulfur bacteria that the researchers cloned and analyzed. They found chlorosomes, certain pigments and compounds that all are used by other bacteria to harness sunlight energy, even though this microbe was nowhere near any sunlight.

Green sulfur bacteria require sulfur, carbon dioxide and light to exist. With light in the form of geothermal radiation, the plume region is the only spot that has these three things for more than 1,300 miles.

Beatty believes it is unlikely sunlight-using bacteria somehow drifted down to the Pacific's bottom.

Instead, the plume organism probably is a new species of green sulfur bacteria that might have evolved from ancient vent dwellers. Beatty thinks other photosynthetic bacteria may live at the vents, but doubts many other light lovers could survive under such dim conditions.

"Sunlight has a huge wavelength range, whereas geothermal radiation lacks the short wavelength region of sunlight," Beatty explained to Discovery News.

"At the temperatures of typical deep sea vents, the radiation in the wavelength range that is detected by the human eye (around 400 to 750 nanometers) is too weak to be seen."

John Allen, professor of biochemistry at the University of London, said the new discovery is "intriguing" and "exciting." He said it fuels the theory that Earth's plants once all began life deep underwater.

"There was a suggestion about 10 years ago from (scientist) Euan Nisbet and co-workers that photosynthesis evolved from an infrared photoreceptor system used by chemotrophic (chemically nourished) bacteria in order to 'tune in' to the energy supply of hydrothermal vents," Allen told Discovery News. "Dr. Beatty's discovery could be taken to support that."

Allen said other researchers have proposed that life is a consequence of geochemistry and will arise on any wet, rocky and lit planet.

Since geothermal radiation from vents and alkaline springs now appears to fulfill the light requirement, that opens the possibility of life on other planets, such as Mars, with possible underground water sources.

Allen is unsure what other alien or Earthly organisms could exist on vent light.

"It seems quite unlikely that there could be eukaroytic or multicellular phototrophs — plants and algae — in such an environment, but who really knows," he said. "There are always surprises."