02619nas a2200205   4500008004100000245006000041210006000101260006000161300000800221490001000229520198900239653001302228653002702241653001302268653001702281653001002298100002402308700003302332856004802365       2024                        eng d00aMetagenomic analysis of Antarctic microbial communities0 aMetagenomic analysis of Antarctic microbial communities  aAlbuquerque, NM, USAbUniversity of New Mexicoc06/2024  a1360 vPh.D.3 a<p>The research presented in this dissertation focuses on microbial roles in biogeochemical cycling in Antarctic aquatic environments. The major objective of my research was to examine the impact of biotic and abiotic pressures on nutrient cycling in microbially dominated systems. I used three perennially ice covered lakes in the McMurdo Dry Valleys (MDVs) along with subglacial lakes Whillans and Mercer as natural case studies. The MDVs are located in Victoria Land, East Antarctica and have been studied since 1993 as part of the McMurdo Long Term Ecological Research Project. Viruses in the MDVs were shown to be seasonally abundant and have high infection rates. My work built upon this previous research by showing that viruses are also diverse and potentially re-direct host metabolism through auxiliary metabolic genes (AMGs). Subglacial lake Whillans and Mercer lie underneath 800 and 1100 meters of ice respectively beneath the West Antarctic Ice Sheet. Previous studies in subglacial lakes Whillans have shown an active prokaryotic community. Through viral-like particle counts, microscopy, and metagenomics, we established the presence and potential metabolic influence of viruses in both Whillans and Mercer. In MDV lakes have an extensive high-throughput DNA dataset studying microbial communities through the 16S rRNA gene. We used metagenomic sequencing within two MCM lakes at multiple depths to build upon these previous datasets by annotating metagenomically assembled genomes for functional characteristics. This project highlights the lakes&#39; vertical redox gradient, showing that dominant taxa, nutrient cycling genes, and metabolic potentials change down the water column. The MDVs serve as a biological indicator for climate change in continental Antarctica and functional changes serve as important indicators of climate change. Taken together, this dissertation shows the importance of multi-kingdom microbial function under oligotrophic conditions.</p>10abacteria10abiogeochemical cycling10afunction10ametagenomics10avirus1 aRobinson, David, M.1 aTakacs-Vesbach, Cristina, D.  uhttps://www.proquest.com/docview/311991058501901nas a2200169   4500008004100000245010500041210006900146260004900215490000900264520132500273653001301598653001201611653001301623100002401636700002601660856004501686       2018                        eng d00aMicrobial and CO2 responses to water stresses show decreased productivity and diversity through time0 aMicrobial and CO2 responses to water stresses show decreased pro  aProvo, UTbBrigham Young Universityc05/20180 vM.S.3 a<p>Some bacterial taxa when stimulated by water additions will break dormancy, grow, and become dominant members of the community and contribute significant pulses of&nbsp;CO<sub>2</sub> associated with the rewetting event. These pulses of activity are associated with high levels of bacterial productivity in soils. (Aanderud et al. 2011) We examined the bacterial taxa that resuscitate and become metabolically active following two forms of water stress (soil drying- rewetting and freeze-thaw cycles) and we captured and measured the CO<sub>2</sub> emanating from those soils. Specifically, We used target metagenomics, which uses a specific gene pool within bacteria that is associated with a function of an ecological process, in this case active (16S rRNA communities) bacteria and all bacteria (16S rRNA communities) during drying-rewetting and freeze-thaw cycles. We measured an array of community dynamics (i.e., evenness, richness, diversity, relative abundance of taxa, and network analyses between taxa) as dry soils are rewetted and as frozen soils thaw multiple times in three cold desert soils. Soils from all three locations exhibited some similar bacterial taxa and gene function but were large in part their own community derived from the evolutionary history of the continent in which they reside.</p>10adormancy10aPiCRUST10aturnover1 aRobinson, David, M.1 aAanderud, Zachary, T.  uhttps://scholarsarchive.byu.edu/etd/6830