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Appl. Environ. Microbiol. doi:10.1128/AEM.01710-08
Copyright (c) 2008, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

A comparative characterization of the microbial diversity in an artificial microbialite model and a natural stromatolite

Department of Microbiology and Cell Science, University of Florida, Space Life Sciences Laboratory, Kennedy Space Center, FL 32899

^* To whom correspondence should be addressed. Email: jfoster{at}ufl.edu.

	Abstract

Microbialites are organosedimentary structures that result from the trapping, binding, and lithification of sediments by microbial mat communities. In this study we developed a model artificial microbialite system derived from natural stromatolites, a type of microbialite, collected from the Exuma Sound, Bahamas. We demonstrated that the morphology of the artificial microbialite is consistent with the natural system, in that there is a multi-layered community containing a pronounced biofilm on the surface, a concentrated layer of filamentous cyanobacteria in the top 5 mm, and a lithified layer of fused oolitic sand grains in the subsurface. The fused grain layer was predominantly comprised of the calcium carbonate polymorph aragonite, which corresponded to the Bahamian stromatolites. The microbial diversity of the artificial microbialites and natural stromatolites was also compared using automated ribosomal intergenic spacer analysis (ARISA) and 16S rRNA gene sequencing. The ARISA profiling indicated that the Shannon indices of the two communities were comparable, and that overall diversity did not significantly decrease in the artificial microbialite model. Bacterial clone libraries generated from each of the three artificial microbialite layers and natural stromatolites indicated that the cyanobacterial and crust layers most closely resemble the ecotypes detected in the natural stromatolites, and are dominated by Proteobacteria and Cyanobacteria. We propose that such model artificial microbialites can serve as experimental analogues for natural stromatolites.