Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)


Biological Sciences

Committee Member

Dr. Harry D. Kurtz, Jr., Committee Chair

Committee Member

Dr. Barbara J. Campbell

Committee Member

Dr. J. Michael Henson

Committee Member

Dr. David L. Freedman


Sandstone outcrops in the Grand Staircase Escalante National Monument, Utah are host to cryptoendolithic communities dominated by cyanobacteria. These communities produce extracellular polymeric substances that not only aid their survival, but also support other heterotrophic bacteria. Developing a better understanding of the role of these cryptoendolithic communities requires a deeper knowledge of the microbial diversity present. We analyzed the cryptoendolithic bacterial communities in the Jurassic Navajo Sandstone samples collected from several microgeological features associated with a large sandstone dome. These communities clustered into distinctive groups that correlated with topography, suggesting that moisture availability plays an important role in shaping the community structure in this microhabitat. Comparisons of diversity between these distinctive groups showed that a core bacterial community exists in this habitat. The overall bacterial community structure was dominated by Cyanobacteria, Proteobacteria, Bacteroidetes and Actinobacteria. Cyanobacteria were chiefly represented by Leptolyngbya in this habitat while the genus Acidiphilium was particularly abundant in the class Alphaproteobacteria. In contrast, the major inhabitants of the cryptoendolithic communities in the Entrada Sandstones are Cyanobacteria followed by Proteobacteria, Actinobacteria, Bacteroidetes and Deinococcus-Thermus. Cyanobacteria were chiefly represented by Chroococcidiopsis in this habitat while the genus Truepera belonging to the phyla Deinococcus-Thermus had a notable presence. The differences in the bacterial composition of the Navajo and Entrada cryptoendolithic habitats are attributed to the varying sand grain size and distribution patterns which affects porosity and moisture availability in the underlying substrate. The number of unclassified OTUs found in both the cryptoendolithic habitats suggests that abundant, unexplored microbial diversity exists in this microecosystem, identifying a conservation value for these communities. EPS produced by both the natural and laboratory grown cryptoendolithic communities are capable of binding divalent metal cations (Fe, Mn, Mg, Cu, Zn), all essential cofactors for oxygenic photosynthesis. Based upon these data, we conclude that the EPSs produced by these cryptoendolithic communities act as a biofilter to bind and concentrate essential metal ions, to provide a source of key nutrients for cellular metabolism. This study sets the premise for elaborating on the ecological functions of cryptoendolithic communities in sandstones.

Included in

Microbiology Commons



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