Description
The aerobic oxidation of methane through a bacterial platform provides new possibilities and solutions in the fields of waste management and compound synthesis. While much is known on a broad metabolic level, the initial steps of methane oxidation are still a subject of discussion. This thesis presents an examination of three predicted possible methane oxidation modes (Direct, Uphill and Redox) within the haloalkaliphilic methanotroph Methylotuvimicrobium alcaliphilum 20ZR. Growth and non-growth ATP maintenances were measured, and experimental data were used with an in silico analyses to identify which modes were most likely. Growth and gas consumption metrics were measured in reduced media lacking substrates for alternative electron acceptors. It was determined that the elimination of alternative electron acceptors, such as nitrate and sulfate, had no significant effect on the O2: CH4 consumption ratio. The experimental data showed, that O2:CH4 consumption rations are below 1.5, ruling out Redox as a potential model. Proteomic data from batch cultures and continuous growth cultures across reduced media, media with and media without copper that the alternative methanol dehydrogenase XoxF could be a key component in the initial stages of methane oxidation. An analysis of important electron transport cytochromes across phyla of methanotrophs revealed conserved components cytochrome cL, cytochrome c oxidase, and cytochrome b as the most prevalent. Phylogenetic analysis of these cytochromes indicated no horizontal gene transfers. The results of this works should be important in developing new models for the initial steps of methane oxidation.
