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Radiation-Resistant Microbe Found in Chilean Desert

By Kate Ruder


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Extremophiles

Shuttle view of the Atacama Desert.

A new species of Deinococcus bacteria has been discovered in the Atacama Desert in Chile. Some areas of the desert receive virtually no measurable rainfall and are among the driest places on Earth, while other parts are moist enough to support plants and microbes in the soil.

The newly found microbe is resistant to high doses of radiation as its cousin Deinococcus radiodurans is, says Fred A. Rainey of Louisiana State University in Baton Rouge, a member of the research team.

D. radiodurans has been nicknamed toughest microbe on earth for its ability to repair its DNA after radiation and drought. Many scientists study this organism to learn about DNA repair in humans, and to study ways to engineer radiation-resistant microbes that could clean up toxic waste sites.

Rainey and his colleagues collected soil samples from various places in the desert, which extends 700 miles along the coast of Northern Chile, from the Pacific Ocean to the Andes Mountains. The researchers take double-traction trucks into the Atacama Desert to collect samples, and must carry in their water.

The driest area of the desert where virtually no bacteria were found.

In a separate finding and in a different area than where the new microbe was discovered, the researchers analyzed soil in the driest part of the desert for evidence of DNA. Even the famously barren Sonora and Mohave Deserts support large populations of bacteria but in this part of the Atacama Desert, scientists found virtually no signs of life.

The dry and barren soils in the Atacama are remarkably similar to soil found on Mars during the Viking expeditions to the red planet in the 1970s. Scientists have disagreed about the results from experiments on the Martian soil.

Experiments the scientists carried out on the Atacama soil were similar to those performed on Martian soil. The absence in the Atacama soil of detectable life as we know it confirms that the Viking expeditions likely found no life on Mars.

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However, it is still possible that life exists on Mars, says Rafael Navarro-González of the Universidad Nacional Autónoma de México, who led the study.

The technology to detect new forms of life is improving. The conditions of the Atacama Desert could help researchers design better experiments for probing Martian soil for life.

Details of the newly discovered bacterium are expected in early 2004.

Navarro-González, R. et al. Mars-Like Soils in the Atacama Desert, Chile, and the Dry Limit of Microbial Life. Science 302, 1018-1021 (November 7, 2003).

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