Microbial communities play critical roles in biogeochemical cycles of aquatic and terrestrial ecosystems, but studies of soil microbial communities have been limited by the diversity and complexity found in most ecosystems. Here we report on work investigating the functional diversity of microbial mat and underlying soil communities in the McMurdo Dry Valleys of Antarctica across a gradient of phosphorus availability on glacial tills of distinct age and mineral composition in Taylor Valley, Antarctica. Microbial mat and soil DNA were extracted and sequenced on an Illumina NextSeq500 in a 150 bp paired end format. Raw sequences were uploaded to the MG-RAST server for processing and annotation. Community taxonomic and functional annotation were determined using the RefSeq and SEED Subsystem databases, respectively. The results revealed significant variation in microbial mat community taxonomic composition between the two tills, strongly associated with visual assessment of mat morphology, e.g., "black" and "orange" mats, and soil N:P ratios. The underlying soil microbial communities did not exhibit significant differences in diversity between the two tills, but community composition varied significantly across gradients of soil chemistry, particularly extractable-phosphate content even within tills. The relative abundance of biogeochemistry-relevant pathways determined from the SEED database varied amongst soil microbial communities between the two tills. For example, microbial mat communities exhibited significant variation in the relative abundance of key nitrogen and phosphorus metabolism associated genes strongly associated with the underlying soil N:P. These results suggest that spatial variation in geochemistry influences the distribution and activity of microbial mats, but that the microbial mats themselves also exert a significant homogenizing effect on the underlying soil communities and some of the key biogeochemical processes they facilitate. / Master of Science / Microbial communities play critical roles in the processes of aquatic and terrestrial ecosystems. Still, studies of soil microbial communities have been limited by the complex nature of the ecosystems we study. This study examined the diversity of microbial communities in the McMurdo Dry Valleys of Antarctica, specifically looking at how different levels of phosphorus availability in the soil affected microbial function. We used DNA sequencing and databases to determine the taxonomic and functional makeup of these communities. We found that while the microbial mat communities varied significantly based on soil chemistry and appearance, the underlying soil microbial communities did not. We also found evidence suggesting that the microbial mats played a role in regulating some of the key ecosystem processes in the soil. Overall, this study sheds light on how microbial communities are impacted by their environment and how they, in turn, impact their surroundings.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/115384 |
| Date | 08 June 2023 |
| Creators | Risteca, Paul Joseph |
| Contributors | Biological Sciences, Barrett, John E., Aylward, Frank O., Brown, Bryan L., Gray, Austin D., Haak, David C. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf, application/pdf |
| Rights | Creative Commons Attribution 4.0 International, http://creativecommons.org/licenses/by/4.0/ |
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