Theses and Dissertations at Montana State University (MSU)
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Item Microbial adaptation to cultivation stress using storage compounds(Montana State University - Bozeman, College of Agriculture, 2022) Arnold, Adrienne Dale; Chairperson, Graduate Committee: Ross Carlson; This is a manuscript style paper that includes co-authored chapters.Methanotrophs and green algae are microorganisms that grow on single carbon substrates. Methanotrophs are bacteria that use methane as their carbon source, and green algae are eukaryotic phototrophs that grow on CO 2. They are of interest both as primary producers in the environment and as biological catalysts for the conversion of greenhouse gases into value-added compounds. Understanding how methanotrophs and green algae adapt to cultivation stresses is key to understanding carbon cycling in the environment and in industrial settings. This work uses stoichiometric metabolic modeling to investigate the role of carbon storage compounds in the metabolism of C1-utilizing organisms. Storage compounds are accumulated as intracellular reserves of polysaccharides or lipids, which can be catabolized under stress conditions to provide carbon and energy to the cell. Catabolism of carbon storage compounds often results in the excretion of multi-carbon organic compounds that can be utilized as carbon substrates by other members of the microbial community. In silico metabolic models were developed for methanotroph and algal systems and used to examine the breakdown of storage compounds in response to common cultivation stresses. For the aerobic methanotrophs, predictions focused on the use of polyhydroxybutyrate and glycogen in adaptation to O 2 limitation. For the green algae, starch and triacylglycerol reserves are analyzed as sources for compatible solutes, which are produced by cells in response to high salinity conditions. Metabolic modeling of storage compound utilization by methanotrophs and algae helps elucidate the role of these organisms as primary producers and presents an opportunity for industrial production of multi-carbon compounds from single carbon substrates.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.