Theses and Dissertations at Montana State University (MSU)
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Item Influence of lithogenic energy on subglacial microbial community composition(Montana State University - Bozeman, College of Agriculture, 2021) Dunham, Eric Corwin; Chairperson, Graduate Committee: Eric Boyd; John E. Dore, Mark L. Skidmore, Eric E. Roden and Eric S. Boyd were co-authors of the article, 'Lithogenic hydrogen supports microbial primary production in subglacial and proglacial environments' in the journal 'Proceedings of the National Academy of Sciences of the United States of America' which is contained within this dissertation.; K. Rebecca Mitchell, Mark L. Skidmore and Eric S. Boyd were co-authors of the article, 'Influence of ferric iron on community composition in a basaltic glacial catchment' which is contained within this dissertation.Chemosynthesis, the generation of biomass using chemical energy, supported life on early Earth and continues to sustain contemporary light-independent ecosystems. The mechanisms of nutrient release from the geosphere are critical to understanding the present and historical distribution and diversity of life. Glaciers release such nutrients through comminution of bedrock, continuously resurfacing reactive minerals that can be colonized and exploited by chemosynthetic microorganisms. Bedrock mineralogy influences the nutrients available in these environments, but little is known about which nutrients are most important or how they affect microbial community composition, particularly in catchments overlying igneous bedrock like basalt. Iron and silicate minerals, common in basalt, readily generate both reductants such as H 2 and oxidants such as Fe(III) through interactions with water. Abundant H 2 in meltwaters of the basalt-based Icelandic glacier Kotlujokull (KJ) were found to support sediment microbial communities better adapted to use H 2 in chemosynthetic metabolism than those found beneath the carbonate-based Robertson Glacier (RG), Canada. KJ communities exhibited shorter lag-times and faster rates of net H 2 oxidation and dark carbon dioxide (CO 2) fixation than those from RG. A KJ sediment enrichment culture provided with H 2, CO 2, and Fe(III) produced a chemolithoautotrophic population related to Rhodoferax ferrireducens, which was also detected using molecular techniques in sediments from Kaldalonsjokull (Kal), another basalt-based Icelandic glacier. The abundance and composition of microbial communities that colonized defined minerals incubated for 12 months in Kal meltwater streams were examined by extracting DNA and sequencing PCR-amplifiable 16S rRNA genes. DNA quantities and the composition of 16S rRNA genes recovered from Kal sediments were most similar to those recovered from incubated Fe(III)-bearing minerals hematite and magnetite, with putative Fe(III) reducers dominating all three communities. These findings point to the importance of bedrock mineral composition in influencing the supplies of nutrients like H 2 and Fe(III) that, in turn, influence the diversity, abundance, and activity of microbial communities in subglacial environments. They further indicate the potential for subglacial habitats to serve as refugia for microbial communities in the absence of sunlight, such as during Snowball Earth episodes, or on icy planets without photosynthetic life.Item Arsenite oxidation by a Hydrogenobaculum sp. isolated from Yellowstone National Park(Montana State University - Bozeman, College of Agriculture, 2002) Donahoe-Christiansen, JessicaItem Geochemical characterization of sulfide mineral weathering for remediation of acid producing mine wastes(Montana State University - Bozeman, College of Agriculture, 1993) Jennings, Stuart Russell; Chairperson, Graduate Committee: Douglas J. DollhopfThe generation of acid mine drainage as a consequence of sulfide mineral oxidation is a widespread source of resource degradation. The objective of this investigation was to evaluate the influence of sulfide mineral weatherability on acid generation processes. In addition to acid generation by pyrite, the weathering characteristics of common sulfide minerals was investigated and correlated to detection by acid-base account (ABA) methodologies. The influence of particle morphology, and not particle size, was found to exert the dominant control on mineral weathering processes. Massive morphology particles generated acid at a significantly greater rate than euhedral morphology samples. Acid generation was a consequence of mineral dissolution which occurred nonuniformly across the surface of minerals during oxidation. Mineral surface weathering occurred at sites of excess energy including grain edges, steps, defects, microcracks and inclusions, resulting in the formation of etch pits. Massive morphology particles exhibited the greatest density of crystalline defect, and had the greatest rate of oxidation. Sulfide minerals found to be acid generating, in addition to pyrite, include marcasite, pyrrhotite, arsenopyrite, chalcopyrite and sphalerite. Minerals containing sulfur in the atomic structure which were not acid producing include barite, anhydrite, gypsum, anglesite, jarosite, chalcocite and galena. Delineation of acid producing and nonacid producing sulfur forms by ABA extraction methods, a standard operating procedure used in the United States, was determined to be ineffective. Effective mineral classification, particle morphology identification and observation of mineral weathering processes were accomplished by scanning electron microscopy. Accurate assessment of sulfur form distribution and sulfide mineral weathering characteristics are required for effective remediation of sites impacted by mining.Item Influence of ruminal minerals on fiber utilization and supplementation on intake and nutrient balance of ewes(Montana State University - Bozeman, College of Agriculture, 1987) Harris, Katherine BarnesItem Effects of organic acids and heavy metals on the biomining bacterium : Acidithiobacillus caldus strain BC13(Montana State University - Bozeman, College of Engineering, 2010) Aston, John Earl; Chairperson, Graduate Committee: Brent M. Peyton; William Apel (co-chair)Acidithiobacillus caldus is an important microorganism to biomining and acid-mine formation. However, its degree of characterization is not commensurate to its significance in such systems. Specifically, studies enumerating effects of organic acids and metals on this microorganism are limited. The work presented in this dissertation improves understanding of At. caldus with respect to interactions with these compounds. All experiments discussed in this dissertation used At. caldus strain BC13. The organic acids; pyruvate, acetate, 2-ketoglutarate, succinate, fumarate, malate, and oxaloacetate were each toxic to At. caldus strain BC13. Depending on the organic acid tested, concentrations between 250 and 5,000 uM completely inhibited the growth of At. caldus strain BC13 (chapter two). Subsequent experiments, reported in chapter three, showed that At. caldus strain BC13 used pyruvate as a sole carbon source. Chapter four discusses the toxicities of the heavy metals; lead, zinc, and copper to At. caldus strain BC13. Lead was by far the most toxic metal tested, with an observed minimum inhibitory concentration of 7.5 mM. Conversely, zinc and copper had minimum inhibitory concentrations of 75 and 250 mM, respectively. The sorption of lead, zinc, and copper was also studied, and is discussed in chapter 5. Between pH 5.5 and 7.0, zinc and copper sorbed to At. caldus strain BC13 with similar capacity and affinity as that observed to other acidithiobacilli, however at pH 2.0, significant sorption of zinc and copper to viable cells was observed, whereas previous work did not report sorption of zinc or copper to viable acidithiobacilli cells below pH 3.0. Chapter six reports efforts to qualify changes in protein expression of At. caldus strain BC13 when exposed to organic acids or heavy metals. Matrix assisted laser desorption ionization mass spectrometry and one-dimensional gel electrophoresis qualified the up-regulation of an integral membrane protein with a molecular weight of approximately 25 kDa. Efforts to identify up-regulated proteins were not successful, but any proteins that are regulated in response to organic acids or heavy metals in biomining microorganisms would likely be of commercial application.Item Microbial and geochemical processes controlling the oxidation and reduction of arsenic in soils(Montana State University - Bozeman, College of Agriculture, 2007) Masur, Deanne Christine; Chairperson, Graduate Committee: William P. Inskeep.Arsenic (As) is a common contaminant in soil-water systems, where it exists predominately as arsenate (AsV) or arsenite (AsIII), the latter of which is considered to be the more mobile and toxic form. The amount of arsenite or arsenate in natural water systems is influenced by geochemical conditions and the presence of As transforming microorganisms. Consequently, the goals of this study were to evaluate the effects of: (i) arsenic concentration on microbial populations responsible for As oxidation-reduction in a previously uncontaminated soil, and (ii) phosphate:arsenic ratio on the oxidation or reduction of arsenic. Laboratory column experiments were conducted to evaluate the influence of soil arsenic concentration on microbial community composition and to identify microorganisms and mechanisms responsible for As transformations occurring under aerobic conditions. Indigenous microorganisms within a previously uncontaminated agricultural soil were exposed to arsenite or arsenate at three concentrations (2, 20 and 200 mg As L-1) for approximately 30 days.Item Microbial interactions with arsenite, hydrogen and sulfide in an acid-sulfate-chloride geothermal spring(Montana State University - Bozeman, College of Agriculture, 2008) D'Imperio, Seth; Chairperson, Graduate Committee: Timothy R. McDermott.The work presented in this thesis investigated the importance of hydrogen, sulfide and arsenite in microbial community structure and function within a model Acid-Sulfate- Chloride (ASC) spring in Yellowstone National Park. Previous studies in this spring found that microbial arsenite [As(III)] oxidation is absent in regions of the spring outflow channel where H 2S exceeds ~5 microM. Ex situ assays with microbial mat samples demonstrated immediate As(III) oxidation activity when H 2S was absent or in low concentrations, suggesting the presence of functional As(III) oxidase enzymes in regions of the spring where arsenite oxidation had not been previously observed. Cultivation efforts resulted in the isolation of an As(III)-oxidizing chemolithotroph phylogenetically related to the alpha-proteobacterium Acidicaldus. H 2S concentration appeared to be the most important constraint on spatial distribution of this organism. This was verified with pure culture modeling and kinetic experiments. Additionally, a study is presented that addresses the relative importance of dissolved hydrogen and sulfide for primary production in the same spring. Throughout the outflow channel where these gases could be detected, biological H 2S consumption rates exceeded those of H2 by at least three orders of magnitude. Molecular analysis showed that Hydrogenobaculum-like organisms dominate the microbial community in this region of the spring. Culturing efforts resulted in 30 Hydrogenobaculum isolates belonging to three distinct 16S rRNA gene phylotypes. The isolates varied with respect to electron donor (H 2S, H 2) and oxygen tolerance and requirement. These metabolic physiologies are consistent with in situ geochemical conditions. An isolate representative of the dominant 16S phylotype was used as a model organism for controlled studies to determine whether an organism capable of utilizing either of these substrates demonstrated preference for H 2S or H 2, or whether either electron donor exerted regulatory effects on the other. The organism studied utilized both H 2S and H 2 simultaneously and at rates roughly comparable to those measured in the ex situ field assays. Major conclusions drawn from this study are that phylogeny cannot be relied upon to predict physiology, and that, in ASC springs, H 2S clearly dominates H 2 as an energy source, both in terms of availability and apparent consumption rates.