Theses and Dissertations at Montana State University (MSU)

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    Bacterial and archaeal community diversity in relation to organic carbon consumption and sulfate gradients in the Powder River Basin
    (Montana State University - Bozeman, College of Letters & Science, 2019) Schweitzer, Hannah Doris; Chairperson, Graduate Committee: Matthew Fields and Sara Branco (co-chair); Elliott Barnhart, Al Cunningham and Matthew Fields were co-authors of the article, 'Comparison of attached and planktonic microbial assemblages across geochemically distinct coal seam habitats' submitted to the journal 'International journal of coal geology' which is contained within this dissertation.; Daniel Ritter, Jennifer McIntosh, Elliott Barnhart, Al B. Cunningham, David Vinson, William Orem and Matthew Fields were co-authors of the article, 'Changes in microbial communities and associated water and geochemistry across a sulfate gradient in coal beds: Powder River Basin, USA' submitted to the journal 'Geochimica et cosmochimica acta' which is contained within this dissertation.; Heidi J. Smith was an author and Elliott P. Barnhart, William Orem, Robin Gerlach and Matthew W. Fields were co-authors of the article, 'Linking organic matter degradation and microbial assemblage composition to subsurface methane production in the Powder River Basin' submitted to the journal 'Applied and environmental microbiology' which is contained within this dissertation.; Heidi J. Smith, Elliott P. Barnhart, Boris Wawrik, Amy Callaghan, Luke McKay, Robin Gerlach and Matthew W. Fields were co-authors of the article, 'Metagenomic analysis of recalcitrant rich coal seams from coal seams with varying sulfate concentrations' submitted to the journal 'Applied and environmental microbiology' which is contained within this dissertation.
    The rate limiting step in biogenic coal bed methane production has been attributed to the predominantly recalcitrant composition of coal, making it difficult for bacteria to anaerobically break down into methanogenic substrates. The significance of different carbon (C) cycling pathways involved in the turnover of recalcitrant, terrestrial C under various redox conditions is still a topic of debate, and in fact, unknown C cycling metabolic pathways are still being discovered in sub-oxic and anoxic environments. Redox transitions exist along gradients of increasingly recalcitrant C in many environments, and subsurface environments represent a large reservoir of C. The Powder River Basin in southeastern Montana is a model environment for studying in situ redox gradients for terrestrial subsurface C and were selected to investigate i) the temporal and spatial variation in the microbial assemblage from four different coal seams with varying depth profiles, ii) the physicochemical controls that impact the turnover of recalcitrant coal to methane, and iii) the functional potential for hydrocarbon degradation under different sulfate concentrations. Similar to the methane-sulfate critical zone in marine habitats, the presented work highlights the crucial role sulfate has on microbial assemblages, methane production, and C consumption in shallow coal seams. Given the accepted differences between groundwater and surface-associated communities of subsurface porous media, diffusive microbial samplers packed with native coal material were used to enhance the establishment of microbial communities that better re-capitulated in situ communities. The microbial community inhabiting low sulfate coal seams consisted of sequences indicative of syntrophic bacteria such as Syntrophomonas and Hydrogenophaga which have previously demonstrated degradation of polycyclic aromatic hydrocarbons (PAH) and coupled growth with hydrogenotrophic methanogens. The assemblages inhabiting high sulfate coal seams were comprised of methylotrophic methanogens and sulfate reducing bacteria. Methylotrophic methanogens are observed in methane producing coal seams that have intermediate levels of sulfate, suggesting an important transition role in early stage methanogenesis. Low sulfate microcosms experienced an increase in humic-like material and consumed more C compared to high sulfate conditions that demonstrated changes in more labile C, including amino acid-like molecules. Moreover, we used a highly curated anaerobic and aerobic hydrocarbon degradation (AnHyDeg and AromaDeg) and redox (nitrogen, sulfur, methane cycle) gene database and pipeline to analyze metagenomic samples that were obtained from three different coal beds that had increasing sulfate levels. While the functional potential for methanogenesis (mcrA) was detected in all metagenomes, the diversity and relative quantity of these genes was greater in the coal beds that contained methane. Of interest was a significantly greater percentage of aerobic hydrocarbon degradation genes (dioxygenases) from one of the methane-containing coal bed samples. These metabolic markers were identified in co-assembled metagenomes. These results provide an enhanced understanding of recalcitrant carbon turnover in the terrestrial subsurface under different redox conditions and the presumptive metabolic capacities involved in subsurface C turnover in relationship to biogenic CH4.
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    Biology of acid-sulfate-chloride springs in Yellowstone National Park, Wyoming, United States of America
    (Montana State University - Bozeman, College of Letters & Science, 2007) Boyd, Eric Stephen; Chairperson, Graduate Committee: Gill G. Geesey; Timothy McDermott (co-chair)
    This dissertation investigated the role of biology in several biogeochemical cycles in acid sulfate chloride (ASC) geothermal springs in Yellowstone National Park (YNP). Elemental sulfur (S°) is associated with many geothermal springs, yet little is known about the organisms involved in its cycling. The aqueous and solid phase geochemistry near the source of Dragon Spring, an ASC spring in the Norris Geyser Basin (NGB) of YNP, was used to guide the enrichment and isolation of two novel S°-reducing Crenarchaeota affiliated with the order Desulfurococcales. Both isolates are chemoorganotrophs, dependent on complex peptide-containing carbon sources, S°, and anaerobic conditions for respiration-dependent growth. Physiological characterization suggests the isolates are adapted to the physicochemical conditions of Dragon Spring which is supported by quantitative PCR analysis which indicates that the isolates represent a significant fraction of the microbial community associated with S° precipitates in several ASC geothermal springs in the NGB in YNP.
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