Old bacteria relied on arsenic, not water

WASHINGTON, Aug. 19 (UPI) -- U.S. scientists say they have discovered ancient bacteria that relied on arsenic, rather than water, to grow during photosynthesis.

The discovery, which the scientists said likely dates to a few billion years ago, came in research funded by the National Aeronautics and Space Administration's Exobiology Program and the U.S. Geological Survey.

The finding is said to add an important dimension to the arsenic cycle "and highlights a previously unsuspected process that may have been essential for establishing the arsenic cycle on the ancient Earth," the USGS said. The arsenic cycle occurs when enzymes trigger microorganisms to convert inorganic arsenic to organic arsenicals.

The discovery came during a study of two small hot spring-fed ponds on the southeastern shore of Paoha Island in Mono Lake, Calif.

The research that included scientists from Duquesne University, the University of Georgia and Southern Illinois University appears in the journal Science.