Theses and Dissertations at Montana State University (MSU)
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Item Evaluation of methanotrophic activity and growth in a methanotrophic-heterotrophic co-culture(Montana State University - Bozeman, College of Engineering, 2021) Kilic, Ayse Bengisu; Chairperson, Graduate Committee: Ellen G. Lauchnor; Erika J. Espinosa-Ortiz, Brent M. Peyton and Ellen Lauchnor were co-authors of the article, 'Methane-based bioreactor configurations in value-added product development: a review' submitted to the journal 'Journal of bioscience and bioengineering' which is contained within this thesis.; Erika J. Espinosa-Ortiz, Brent M. Peyton and Ellen Lauchnor were co-authors of the article, 'Evaluation of methanotrophic activity and growth in a methanotrophic-heterotrophic co-culture' submitted to the journal 'Engineering in life sciences' which is contained within this thesis.Methane is a potent greenhouse gas (GHG) and accounts for 20-30% of the GHG emissions globally. In nature, methane is utilized as a sole carbon and energy source by a group of bacteria referred to as methanotrophs. Methanotrophs have been reported to have the ability to form close associations with other microorganisms such as heterotrophic bacteria in the environment. Therefore, understanding methanotrophic activity and growth in a microbial consortium with heterotrophic bacteria is of interest from an environmental and biotechnology perspective. In this study, a methanotroph; Methylocystis sp. NLS7 and a heterotrophic bacterium, Pseudomonas chlororaphis, were co-cultivated in a methane-fed bioreactor with a dialysis membrane device used to separate the species physically. It was hypothesized that the co-culture would exhibit enhanced methanotrophic activity and microbial growth of NLS7 in NLS7- P. chlororaphis co-culture. The methane-oxidation rate and microbial growth rate of NLS7 were evaluated as a functional response variable to the presence of P. chlororaphis. In addition, the effects of NLS7 growth were evaluated on the growth of P. chlororaphis. Our findings indicated that the presence of P. chlororaphis does not have any beneficial effects on Methylocystis sp. NLS7 activity and growth. However, the growth of P. chlororaphis in the co-culture with solely methane as a carbon source indicated that P. chlororaphis is likely gaining carbon and energy from by-products of methane oxidation by Methylocystis sp. NLS7 since P. chlororaphis could not utilize methane as a carbon and energy source. The results of this study give us an important insight into the activity and the growth of methanotrophic consortia in methane-driven ecosystem.Item Chemosynthetic carbon metabolism in thermophiles(Montana State University - Bozeman, College of Letters & Science, 2015) Urschel, Matthew Robert; Chairperson, Graduate Committee: Eric Boyd; Michael D. Kubo, Tori M. Hoehler, John W. Peters and Eric S. Boyd were co-authors of the article, 'Carbon source preference in chemosynthetic hot spring communities' in the journal 'Applied and Environmental Microbiology' which is contained within this thesis.; Matthew R. Urschel, Trinity L. Hamilton, Eric E. Roden and Eric S. Boyd were co-authors of the article, 'Substrate preference and uptake kinetics in a facultatively autotrophic and hyperthermophilic crenarchaeote' submitted to the journal 'Applied and environmental microbiology' which is contained within this thesis.Microbial communities inhabiting high temperature (>73°C) environments are supported by chemical energy, providing a unique opportunity to investigate the processes that supported life prior to the advent of photosynthesis. Previous work has focused on the importance of autotrophy in supporting such communities, and recent reports of organic substrate utilization in several high temperature springs in Yellowstone National Park (YNP), Wyoming, USA suggest that chemosynthetic populations are facultatively autotrophic. Nevertheless, little is known about the factors influencing relative rates of autotrophy and heterotrophy in these systems, and few studies have addressed the potential role of facultative autotrophs in supporting these ecosystems. This work addressed these compelling questions using in situ microcosm assays to directly quantify organic and inorganic substrate transformation rates in 13 geochemically diverse YNP chemosynthetic communities. The results provide the first conclusive evidence that dominant autotrophs in these ecosystems are facultative, and can alter their metabolism over short time spans to preferentially exploit more thermodynamically favorable organic substrates at rates comparable to or exceeding those of inorganic substrate utilization. Multivariate statistical analysis of co-registered substrate transformation rates, geochemical measurements, and phylogenetic data collected from these communities suggests an important relationship between environmental variation, community composition, and the relative importance of autotrophic and heterotrophic metabolisms supporting these communities. Elevated formate utilization rates in crenarchaea-dominated chemosynthetic communities inhabiting acidic, sulfur-rich geothermal springs motivated the isolation of the first hyperthermophilic crenarchaeon (Thermoproteus sp CP80) capable of coupling formate oxidation to elemental sulfur reduction. Physiological characterization demonstrated that CP80 is a facultative autotroph that alters its metabolism to preferentially utilize formate over CO 2. Similar formate utilization characteristics by CP80 and its native population strongly suggests that this and other sulfur reducing crenarchaea may be responsible for high rates of formate utilization in high temperature, sulfur rich YNP systems. Overall, these results indicate an important, previously-underestimated role for organic substrates in supporting chemosynthetic communities inhabiting geochemically diverse YNP hot springs. Future work should focus on identifying additional organic carbon sources, measurement of carbon flux through chemosynthetic communities, and further characterization of the biochemical mechanisms underlying organic and inorganic substrate metabolismin Thermoproteus sp. CP80.Item Control of bacterioplankton activity in a eutrophic lake emphasizing relationships among bacteria, cyanobacteria and nutrients(Montana State University - Bozeman, College of Letters & Science, 1992) Wang, Lizhu