Profiling Bacterial Diversity and Taxonomic Composition on Speleothem Surfaces in Kartchner Caverns, AZ
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ENVIRONMENTAL MICROBIOLOGY
Profiling Bacterial Diversity and Taxonomic Composition on Speleothem Surfaces in Kartchner Caverns, AZ Marianyoly Ortiz & Julia W. Neilson & William M. Nelson & Antje Legatzki & Andrea Byrne & Yeisoo Yu & Rod A. Wing & Carol A. Soderlund & Barry M. Pryor & Leland S. Pierson III & Raina M. Maier
Received: 17 July 2012 / Accepted: 22 November 2012 / Published online: 9 December 2012 # Springer Science+Business Media New York 2012
Abstract Caves are relatively accessible subterranean habitats ideal for the study of subsurface microbial dynamics and metabolisms under oligotrophic, non-photosynthetic conditions. A 454-pyrotag analysis of the V6 region of the 16S rRNA gene was used to systematically evaluate the bacterial diversity of ten cave surfaces within Kartchner Caverns, a limestone cave. Results showed an average of 1,994 operational taxonomic units (97 % cutoff) per speleothem and a broad taxonomic diversity that included 21 phyla and 12 candidate phyla. Comparative analysis of speleothems within a single room of the cave revealed three distinct bacterial taxonomic profiles dominated by either Actinobacteria, Proteobacteria, or Acidobacteria. A gradient in observed species richness along the sampling transect revealed that the communities with lower diversity corresponded to those dominated by Actinobacteria while the more diverse communities Electronic supplementary material The online version of this article (doi:10.1007/s00248-012-0143-6) contains supplementary material, which is available to authorized users. M. Ortiz : J. W. Neilson : A. Legatzki : A. Byrne : R. M. Maier (*) Department of Soil, Water and Environmental Science, University of Arizona, Shantz Bldg Room 429, 1177 E. 4th Street, Tucson, AZ 85721-0038, USA e-mail: [email protected] W. M. Nelson : C. A. Soderlund BIO5 Institute, University of Arizona, Tucson, AZ 85721, USA Y. Yu : R. A. Wing : B. M. Pryor Department of Plant Sciences, University of Arizona, Tucson, AZ 85721, USA L. S. Pierson III Department of Plant Pathology and Microbiology, Texas A&M University, College Station, TX, USA
were those dominated by Proteobacteria. A 16S rRNA gene clone library from one of the Actinobacteria-dominated speleothems identified clones with 99 % identity to chemoautotrophs and previously characterized oligotrophs, providing insights into potential energy dynamics supporting these communities. The robust analysis conducted for this study demonstrated a rich bacterial diversity on speleothem surfaces. Further, it was shown that seemingly comparable speleothems supported divergent phylogenetic profiles suggesting that these communities are very sensitive to subtle variations in nutritional inputs and environmental factors typifying speleothem surfaces in Kartchner Caverns.
Introduction Bacteria have been found in every known ecological niche on earth with the microbial diversity of each niche specifically, finely tuned to exploit the environmental conditions found in that particular ecosystem. Analysis of the microbial dive
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