Life without Sun

MARINE BIOLOGY

Newly discovered photosynthetic bacteria may get all the light they need for metabolism from the dim radiation emitted by deep-sea hydrothermal vents. If the finding is confirmed, the organisms would be the first known to use a light source other than the sun, suggesting the possibility of life in other sunless environments, such as Jupiter's moon Europa.

A group that includes microbiology and immunology professor J. Thomas Beatty at the University of British Columbia, Vancouver; marine biology professor Cindy L. Van Dover at the College of William & Mary, Williamsburg, Va.; and chemistry professor Robert E. Blankenship at Arizona State University, Tempe, isolated the photosynthetic green sulfur bacteria from a single hydrothermal vent in ocean depths not reached by sunlight and cultured them in the lab (Proc. Natl. Acad. Sci. USA 2005, 102, 9306).

Their announcement comes with some strong caveats, however. The authors can't say for sure whether the bacteria are actually indigenous to the vents. There's a chance, they note, that the organisms could have drifted into the collection area from elsewhere, where sunlight could have supported them.

Other marine biologists concur. Colleen M. Cavanaugh, a biology professor at Harvard University, cautions that the bacteria need to be linked to their environment before the discovery can be validated. "But this would certainly be cool, if real," she says.

Linda Jahnke, a microbiologist at NASA's Ames Research Center in Moffett Field, Calif., notes that the violent, unstable conditions surrounding a deep-sea vent don't seem amenable to the bacteria's survival.

Beatty hopes their work will stimulate other groups to look for similar bacteria at other vents. "If we kept finding these organisms repeatedly, then there would be guilt by association," he says.