Theses and Dissertations at Montana State University (MSU)
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Item The biofilm matrix in sulfate-reducing bacterial biofilms: potential roles for electron mediators and large proteins(Montana State University - Bozeman, College of Letters & Science, 2019) Krantz, Gregory Peter; Chairperson, Graduate Committee: Matthew Fields; Kilean Lucas, Erica L.-Wunderlich, Linh T. Hoang, Recep Avci, Gary Siuzdak and Matthew W. Fields were co-authors of the article, 'Bulk phase resource ratio alters carbon steel corrosion rates and endogenously produced extracellular electron transfer mediators in a sulfate-reducing biofilm' in the journal 'Biofouling' which is contained within this dissertation.; Peter J. Walian, Marty Boyl-Davis, Kara De Leon, Judy D. Wall and Matthew W. Fields were co-authors of the article, 'Large extracellular proteins sense hydrodynamic force and drive biofilm formation in Desulfovibrio vulgaris' which is contained within this dissertation.; Marty Boyl-Davis, Kara De Leon, Judy D. Wall and Matthew W. Fields were co-authors of the article, 'Characterization of extracellular biofilm mutants cultivated on 1018 carbon steel in Desulfovibrio vulgaris Hildenborough' which is contained within this dissertation.Sulfate-reducing bacteria grow and form biofilms in soil and benthic environments across much of the Earth's surface. Formation of these prevalent biofilms requires the secretion of an extracellular polymeric substance (EPS) to allow the cells to stick together, as well as adhere to a surface. The specific interactions that occur between EPS components of an SRB biofilm are poorly understood. The data presented in this dissertation suggest the presence of two extracellular mechanisms utilized in these communities. The first mechanism was observed in a study altering the lactate (electron donor) and sulfate (electron acceptor) ratios to create limiting nutrient conditions in Desulfovibrio alaskensis G20 (G20) biofilms. G20 was grown under two conditions: electron donor limited (EDL) and electron acceptor limited (EAL) conditions. When grown on a 1018 carbon steel substrate, the G20 consumes all of the available lactate, and once limited, it turns to the high energy electrons in the Fe 0 for growth. Corrosion rates in the steel increased two fold compared to the EAL condition. Global metabolomic analysis revealed increased lumichrome levels under the EDL condition, which suggested higher flux through the riboflavin/FAD biosynthetic pathway. Previous research showed that synthetically adding riboflavin and FAD increases the corrosion rate of a SRB biofilm on 1018 carbon steel, and paired with these results, suggest G20 produces a flavin-based extracellular electron transfer molecule endogenously, and uses it to harvest high energy electrons from Fe 0 when limited for electron donor. The second mechanism was observed in Desulfovibrio vulgaris Hildenborough (DvH) biofilms grown on glass. Two proteins, DVU1012 and DVU1545 were found to be the most abundant extracellular peptides in a DvH biofilm. Single deletion strains for these proteins grew biofilm similar to the wild type strain, but a double deletion strain had decreased ability to form biofilm, demonstrating that at least one of the peptides must be present in order to form a biofilm. Exposure to increased shear force caused an large increase in wild-type biofilm biomass, yet eliminated the double mutant biofilm. These proteins are required for a DvH biofilm to respond to shear force.Item Ecophysiology of Methanococcus maripaludis and Desulfovibrio vulgaris : the role of structure in relation to function(Montana State University - Bozeman, College of Letters & Science, 2013) Brileya, Kristen Annis; Chairperson, Graduate Committee: Matthew Fields; Laura B. Camilleri and Matthew W. Fields were co-authors of the article, 'Biofilm growth mode optimizes carrying capacity of interacting populations' submitted to the journal 'The ISME journal' which is contained within this thesis.; James M. Connolly, Carey Downey, Robin Gerlach and Matthew W. Fields were co-authors of the article, 'Taxis toward hydrogen gas by Methanococcus maripaludis' submitted to the journal 'Science' which is contained within this thesis.Sulfate-reducing bacteria (SRB) and methanogenic archaea are known to interact in anaerobic environments under a range of conditions, and the nature of the interaction is dependent on the concentration of available carbon and energy sources, electron acceptors and the metabolic potential of the specific genera present. In the absence of sulfate, SRB can participate in a mutualism by product inhibition with hydrogenotrophic methanogens. SRB reduce protons to form hydrogen gas as a methanogenic substrate, and methanogens prevent inhibition of hydrogenase activity in the SRB by consuming the evolved hydrogen, making the interaction beneficial to both parties. This type of interaction can occur in nature when organisms are free-swimming or attached to a surface as biofilm. The impact of structured biofilm on ecosystem function at various scales is becoming increasingly clear, as this growth mode concentrates biomass which can increase the capacity for compound immobilization, affect hydrodynamic flow paths, and leave cells in altered physiological states. In spite of this, few studies have systematically characterized mutualistic interactions within the biofilm state using model organisms. Syntrophic continuous culture of Desulfovibrio vulgaris Hildenborough and Methanococcus maripaludis was monitored from inoculation through steady state for biofilm and planktonic community structure and function in terms of biomass production, lactate oxidation, and methane production. This biofilm was structurally distinct from monoculture biofilms grown under the same conditions and yield of biomass per lactate mass flux or methane produced was much higher when biofilm was present under lactate limitation. The results suggested that biofilm helped optimize carrying capacity of the syntrophic culture. Observations in coculture biofilm of attraction by M. maripaludis to a surface in the presence of a hydrogen-producing biofilm indicated a tactic response in the archaeum. Movement toward favorable conditions, or chemotaxis is a strategy employed across all three domains of life, yet chemotaxis in archaea is still poorly described, and no previous work has demonstrated taxis toward a hydrogen source, like a syntrophic partner, in spite of its role in electron flow in anaerobic communities. Here we present the first direct observation of taxis toward hydrogen, or "hydrogenotaxis" in the archaeum M. maripaludis.