Theses and Dissertations at Montana State University (MSU)
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Item Reductive dissolution of pyrite by methanogens and its physiological and ecological consequences(Montana State University - Bozeman, College of Agriculture, 2022) Payne, Devon; Chairperson, Graduate Committee: Eric Boyd; This is a manuscript style paper that includes co-authored chapters.All life requires iron and sulfur, in particular, for use in metallocofactors of enzymes that catalyze chemistry that is essential for metabolism. In anaerobic environments, iron and sulfur are typically found in their reduced forms (ferrous iron and sulfide, respectively) that will react and form insoluble iron-sulfide minerals, such as pyrite. A consequence of this is that either iron or sulfur are typically limiting in solution, raising the question as to how anaerobes acquire these essential elements under such conditions. Here, it is demonstrated that anaerobic methanogens can reduce pyrite to release iron and sulfur that are assimilated by the cells to meet biosynthetic demands. Through a combination of growth experiments, -omics analyses, and microscopy, a model for the reductive dissolution of pyrite was established. In this model, direct contact between cells and pyrite is required for mineral reduction. When in direct contact, pyrite is reduced and sulfide is released, leaving a pyrrhotite secondary mineral on the surface. Iron solubilized from pyrrhotite reacts with sulfide in the growth medium to yield aqueous iron sulfur clusters that are assimilated by cells. Cells grown on pyrite exhibit phenotypic differences in comparison to traditionally grown cells provided with ferrous iron and sulfide. At a morphological level, pyrite-grown cells were 33% smaller than traditionally grown cells and hyperaccumulated iron as an intracellular mineral. When grown under nitrogen-fixing conditions, cells grown on pyrite had higher cell densities, growth yields, and growth rates in comparison to traditionally grown cells. Molybdate transporters were down expressed in pyrite-grown, nitrogen-fixing cells relative to traditionally-grown cells, consistent with sulfide limiting molybdate availability in the latter condition. Moreover, pyrite-grown cells could fix nitrogen at ~100-fold lower molybdenum concentration than traditionally grown cells, indicating differences in molybdenum requirements based on the iron and sulfur source provided. Together, these data highlight that in contemporary anoxic environments, iron-sulfide minerals are an important and even preferred source of iron and sulfur for methanogens. These findings provide insight into how ancient methanogens could have acquired iron and sulfur on an anoxic early Earth when one or both of these elements were likely only available as metal sulfides.Item Geomicrobiology of hydrogen in Yellowstone Hot Springs(Montana State University - Bozeman, College of Letters & Science, 2019) Lindsay, Melody Rose; Chairperson, Graduate Committee: Eric Boyd; Daniel R. Colman, Maximiliano J. Amenabar, Kirsten E. Fristad, Kristopher M. Fecteau, Randall V. Debes, John R. Spear, Everett L. Shock, Tori M. Hoehler and Eric S. Boyd were co-authors of the article, 'Geological source and biological fate of hydrogen in Yellowstone hot springs' which is contained within this dissertation.; Maximiliano J. Amenabar, Kristopher M. Fecteau, R. Vincent Debes II, Maria Clara Fernandes, Kirsten E. Fristad, Huifang Xu, Tori M. Hoehler, Everett L. Shock and Eric S. Boyd were co-authors of the article, 'Subsurface processes influence oxidant availability and chemoautotrophic hydrogen metabolism in Yellowstone hot springs' in the journal 'Geobiology' which is contained within this dissertation.Hydrogen (H 2) connects the geosphere and biosphere in rock-hosted ecosystems and has likely done so since early in Earth's history. High temperature hydrothermal environments, such as hot springs, can be enriched in H 2 and were likely widespread on early Earth. As such, linking the geological processes that supply H 2 to contemporary hot springs and the distribution of extant thermophilic organisms that can utilize H 2 as a component of their energy metabolism can provide insights into the environment types that supported early H 2 dependent life. Using a series of geochemical proxies, I developed a model to describe variable H 2 concentrations in Yellowstone National Park (YNP) hot springs. The model invokes interaction between water and crustal minerals that generates H 2 that can partition into the vapor phase during decompressional boiling of ascending hydrothermal waters. Fractures and faults in bedrock, combined with topographic features such as high elevation, allow for vapor to migrate and concentrate in certain areas of YNP leading to elevated concentrations of H 2. Metagenomes from chemosynthetic communities in YNP springs sourced with vapor-phase gas are enriched in genes coding for enzymes predicted to be involved in H 2-oxidation. A spring in an area of YNP (Smokejumper, SJ3) sourced with vapor-phase gas, that has the highest concentration of H 2 measured in YNP, and that is enriched in hydrogenase encoding genes was chosen to further examine the biological fate of H 2. SJ3 harbors a hyperdiverse community that is supported by mixing of oxidized meteoric fluids and volcanic gases. Transcripts coding for genes involved in H 2 uptake and CO 2 fixation were detected. The processes that control the availability of oxidants and their effect on the activity and abundance of H 2 dependent organisms was also investigated in two paired hot springs. H 2-oxidizing chemoautotrophs utilized different oxidants in the two springs and this underpinned differences in H2 oxidation activity and their identity. Together, these observations indicate that the subsurface geological processes of decompressional boiling and phase separation influence the distribution, identity, and activity of hydrogenotrophs through their combined effects on the availability of H 2 and oxidants.Item Mineralogical and geochemical characterization of two Sulfolobales harboring hot spring systems : Rabbit Creek and Ragged Hills, Yellowstone National Park, WY, USA(Montana State University - Bozeman, College of Letters & Science, 2003) Hanna, Braden ThomasItem Regional context, internal structure, and microbiological investigation of the Lone Peak Rock Glacier, Big Sky, Montana(Montana State University - Bozeman, College of Letters & Science, 2011) Florentine, Caitlyn Elizabeth; Chairperson, Graduate Committee: Mark L. Skidmore; Mark Skidmore, Marvin Speece, Curtis Link, William Locke, Christina Carr, and Colin Shaw were co-authors of the article, 'The role of geology in rock-glacier distribution and internal structure: a case study from SW Montana' in the journal 'Journal of geophysical research earth surface' which is contained within this thesis.; Mark Skidmore and Scott Montross were co-authors of the article, 'Rock-glacier ice as a microbial habitat' in the journal 'Journal of glaciology' which is contained within this thesis.This thesis is the first to the author's knowledge to conduct a holistic investigation of the physical, chemical and microbial properties of a rock glacier. The Lone Peak Rock Glacier (LPRG) is located in the Madison Range of southwest Montana on Big Sky Resort property. This thesis focuses on three scales of investigation: regional, landform, and micro. Regional-scale analysis assessed the role of geology and topography as factors in determining rock-glacier distribution in SW Montana above 2000m. Rock glaciers across alpine landscapes in southwest Montana are preferentially distributed according to rock type, with more rock glaciers occurring in intrusive, foliated intrusive and metamorphic catchments relative to the areal proportion of these rock types than in extrusive and sedimentary catchments. This preferential distribution according to catchment geology is likely due to the affect that geology has on topography and provision of talus. Landform-scale analysis focuses on internal structure, flow dynamics and surface topography of the LPRG. The relationship between surface topography and subsurface structure is explained by passive roof duplex faulting. This finding has implications for rock-glacier flow dynamics and the development of transverse ridges, a common surface feature of rock glaciers studied worldwide. Micro-scale analysis characterizes microbiological and geochemical properties of rock-glacier ice and evaluates it as a microbial habitat, exploring potential associations between debris content and microbial activity. Amber ice (containing 0.1% debris by weight) appears to be a more suitable microbial environment than debris-poor ice (containing < 0.01% debris). This finding highlights the importance of debris as a potential nutrient and energy source to enhance microbial viability in rock-glacier ice.