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Bacteria use poison to make food

Newly discovered bacteria hint at how early life may have survived in a no-oxygen atmosphere

1:09pm, August 14, 2008
Some bacteria from MonoLake in California do photosynthesis the old-fashioned way — really old-fashioned: They use arsenic instead of oxygen.

Arsenic photosynthesis may be an ancient form of metabolism, dating from the earliest days of life on Earth before oxygen filled the atmosphere, says Ronald Oremland, a microbiologist and geochemist with the United States Geological Survey in Menlo Park, Calif. Oremland and his colleagues describe the two types of newly discovered bacteria in the Aug. 15 Science.

One of the first steps most organisms perform in photosynthesis is to split water molecules, creating oxygen. Oxygen donates energy in the form of electrons to other molecules, setting off a chain reaction that eventually results in the building of sugars for the organism’s own food. For the red and green bacteria found in MonoLake, arsenic plays the role of oxygen.

Both of the newly discovered bacteria

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