Dissertation Defense - Wenyu Gu

Start Date: 
Friday, April 7, 2017 - 9:00am to 10:30am

GG Brown 2029

Presenter: 
Wenyu Gu

Title: "Metals and Methanotrophs"

Methanotrophs are a group of bacteria that use methane as their sole carbon and energy source. These microbes have various applications including methane removal, biodegradation of halogenated hydrocarbons, and valorization of methane to various products including biofuels, bioplastics, and single cell protein. Current obstacles for the application of aerobic methanotrophs include our incomplete understanding of their metabolism and genetics. This work studies the methanotrophic response to metals, i.e., copper and rare earth elements (REEs), with the goal of achieving better control of methanotrophic activity.

Methanotrophs produce a novel copper-binding compound called methanobactin. This compound plays a key role in controlling methanotrophic activity, and has also been shown to be effective in the treatment of Wilson disease, an autosomal recessive disorder where the human body cannot correctly assimilate copper. First, the uptake mechanism of mb was investigated. mbnT, encoding for TonB-dependent transporter, was knocked-out in Methylosinus trichosporium OB3b. The mbnT::Gmr mutant was able to synthesize and secrete mb but not take it up as evidenced by significant decrease in copper uptake when grown at presence of exogenous mb. Second, the biosynthesitic pathway of mb was investigated. Specifically, mbnN, encoding for an aminotransferase, was disrupted in M. trichosporium OB3b. mb produced by this mutant has only one of the two oxazolone rings and the C-terminal methionine was missing. This study lays the foundation for achieving fine-tuning mb structure and for enhancing its production for potential applications.

REEs were also shown to control key parts of methanotrophic metabolism, i.e., the expression of alternative forms of methanol dehydrogenases. This effect, however, were only observed in the absence of copper, indicating cross-regulation by copper and REEs. The whole transcriptomic response to copper and/or cerium in M. trichosporium OB3b was studied using transcriptomic and RT-qPCR assays. Interestingly, the largest difference in gene expression was observed when both copper and cerium were present. Many genes were upregulated, most notably multiple steps of the central methane oxidation pathway, the serine cycle, and the ethylmalonyl-CoA pathway, indicating more efficient carbon assimilation.

Chair: Jeremy Semrau

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