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Vol. 72, No. 2, 2006; Pages: 1708–1715

Diversity of Microorganisms within Rock Varnish in the Whipple Mountains, California†

K. R. Kuhlman,1* W. G. Fusco,2 M. T. La Duc,1 L. B. Allenbach,2 C. L. Ball,2 G. M. Kuhlman,1 R. C. Anderson,1 I. K. Erickson,3 T. Stuecker,1 J. Benardini,2 J. L. Strap,2 and R. L. Crawford2

Planetary Science Institute, 1700 East Fort Lowell Rd., Suite 106, Tucson, AZ 85719.


Rock varnish from Arizona’s Whipple Mountains harbors a microbial community containing about 108 microorganisms g-1 of varnish. Analyses of varnish phospholipid fatty acids and rRNA gene libraries reveal a community comprised of mostly Proteobacteria but also including Actinobacteria, eukaryota, and a few members of the Archaea. Rock varnish represents a significant niche for microbial colonizationRock varnish (also known as desert varnish) is a dark, thin (usually 5 to 500 m thick), layered veneer composed of clay minerals cemented together by oxides and hydroxides of manganese and iron (11, 20, 56, 63, 64). Nineteenth century references to rock varnish include those of Humboldt (42) and Darwin (14). Modern observations of varnish were initiated with the studies of Laudermilk (49) and Engel and Sharp (25); however, despite decades of study, the nucleation and growth mechanisms of rock varnish remain a mystery (11, 18, 37, 44, 57, 58).

Keywords:microbial community;microorganisms g-1;phospholipid fatty acids;eukaryota;rRNA gene;Proteobacteria;Actinobacteria;Archaea;taxonomy.

Corresponding author: Tel (520) 622-6300; Fax (520) 622-8060

E-mail: kim@psi.edu


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