In the textbook description of photosynthesis, sunlight fuels the production of sugars that are in turn converted into fuel for the photosynthetic organism. But a recent discovery from the deep blue sea may force a revision of that account. Scientists have found a photosynthetic bacterium that doesn't live off the light of the sun. Instead, it uses the dim light given off by hydrothermal vents some 2,400 meters below the ocean's surface.

J. Thomas Beatty of the University of British Columbia and his colleagues first encountered the bacterium, GSB1, in samples collected from a vent field called 9 North, which is located off the coast of Mexico. The bacteria thrive in the scalding water shooting from the vent, which reaches temperatures near 300 degrees Celsius. DNA analysis identified the organism as a member of the green sulfur bacteria family that relies solely on photosynthesis to survive. "This is startling in the sense that you do not expect to find photosynthesis in a region of the world that is so completely dark," remarks study co-author Robert Blankenship of Arizona State University.

The bacteria have a sophisticated antenna system that allows them to collect the low light emanating from hydrothermal vents, the researchers explain in a report published online this week by the Proceedings of the National Academy of Sciences. This light energy is then transferred to the organism's reaction center, where photosynthesis takes place. "This shows that photosynthesis is something that is not limited only to the very surface of our planet," Blankenship says. "It lets you consider other places where you might find photosynthesis on Earth as well as on other planets."

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