The Role of Two-Component Systems in the Nitric Oxide Stress Response of Escherichia Coli

Abstract

The virulence of a number of bacterial pathogens is dependent on their ability to survive in the presence of and detoxify nitric oxide (NO•). A greater understanding of the NO• metabolism of pathogenic bacteria can lead to new therapeutic targets. This thesis explores the role two-component systems (TCS) have in the NO• metabolism of Escherichia coli. TCS were identified as being important to the NO• stress response of Helicobacter Pylori, and it was hypothesized that they might have a similar function in E. coli. The response to NO• stress was characterized for a select group of TCS in E. coli. It was found that in microaerobic conditions, oscillations in the concentrations of NO• and O\(_{2}\), which are present in wild-type E. coli, were eliminated in strains where the components of the ArcAB TCS were deleted. The mechanism underlying this phenotypic difference was further studied. The roles of the NO• dioxygenase Hmp, the NO• reductase NorV, and the cytochrome quinol oxidases were considered, and it was found that the deletion of one of the single cytochrome quinol oxidases, cydB, was phenotypically similar to the ΔarcA strain.