| Description |
Extraintestinal Pathogenic Escherichia coli (ExPEC) is a common member of the human gastrointestinal (GI) microbiota. While ExPEC causes no overt pathologies within the GI tract, it can disseminate and cause diseases such as urinary tract infections, sepsis, and neonatal meningitis. Widespread antibiotic resistance within ExPEC is leading to limited treatment options available for patients. My dissertation work has aimed to understand how ExPEC survives the variety of stresses it encounters in the GI tract and during infection. These stresses include nutrient deprivation, oxygen and nitrogen radicals, extremes in pH, changes in osmotic pressure, and host immune effector cells and the antimicrobial compounds they secrete. ExPEC can modify its stress responses through posttranscriptional regulation, where gene expression is controlled at the level of RNA. In the first part of my dissertation, I explore the role of small non-coding RNAs (sRNA) in the oxidative stress response of ExPEC. sRNAs base-pair to their target mRNA to inhibit or promote translation. I show that the individual deletion of two sRNAs, MicC and Spot 42, led to a significant decrease in growth of ExPEC during exposure to superoxide. I also go on to show that micC knockout strain is defective in its ability to colonize the urinary tract, bloodstream, and gut. My work indicates that sRNA can have vast effects on the stress resistance and virulence of ExPEC. In the second part of my dissertation, I explore the impact of the tRNA modifying iv enzyme, MiaA, to the stress response of ExPEC. MiaA is a tRNA prenyltransferase which adds a prenyl group to tRNAs that decode UNN-codons. The deletion of MiaA has widespread effects on the stress response of ExPEC. Within this work, I delve more deeply into ExPEC response to high salt, showing that during high salt exposure, ExPEC down-regulates MiaA leading to lower levels of modified tRNAs. As changing levels of the ms2i6A modifaction affect the fidelity of translation as well as the proteome, we hypothesize that ExPEC may vary MiaA levels to alter translation and the spectrum of proteins expressed in order to better respond to stress. |
