ASGSB 2003 Annual Meeting Abstracts


NITRATE-REDUCING BACTERIA FROM CHILE'S ATACAMA DESERT (A POTENTIAL MARTIAN ANALOG).  C. J. Spurlock1, Shawn M. Zimmerman1, Christopher P. McKay2, and David J. Thomas11Science Division, Lyon College, Batesville, AR; 2Space Science Division, NASA Ames Research Center, Moffett Field, CA.

   The Chile's Atacama Desert contains vast nitrate deposits.  Nitrates usually do not persist in the environment because of their solubility and consumption by microorganisms.  Many bacteria utilize nitrate both as a nitrogen source and as an electron acceptor for respiration.  Earlier studies indicated that native nitrogen-cycling bacteria are absent from the Atacama soil.  Presently, the Atacama Desert receives less than 2 mm of precipitation per year.  However, evidence of long-past (~20,000 years ago) monsoons exists, and the desert may have once supported a more active biosphere.  Therefore, we suspect that nitrogen-cycling microbes are present in the sub-surface soil of the Atacama Desert but are currently dormant due to the lack of water in the area.  We received Atacama soil samples from NASA Ames Research Center.  Subsamples were inoculated into denitrification-fluorescence broth, and resultant bacteria were streaked onto D-F agar for isolation.  Isolated bacteria were characterized with standard staining and physiological procedures.  As of mid-July, we have isolated two strains of nitrate-reducing bacteria.  The bacteria are Gram-positive rods that reduce nitrate to nitrite, but do not completely denitrify to dinitrogen.  Most likely, they are the same species.  Ongoing characterization of the bacteria will be presented.  The soil sample from which these bacteria were isolated was taken from the near-surface horizon; thus at this time, we cannot ascertain whether these bacteria are native to the Atacama, wind-blown "migrant" bacteria, or human contaminants.  Because of the Atacama Desert's aridity and nitrate-rich soil, it may be a credible analog of possible evaporitic formations on Mars. 

(Supported by Lyon College and NASA Ames Research Center.)


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