Analyzing the Effect of Growth Substrates on Escherichia coli’s Response to Nitric Oxide Stress

Abstract

The virulence of many pathogens is dependent on their ability to defend against NO• stresses. NO• is one of the most ubiquitous antimicrobial produced by the immune system to fight off pathogens. NO• is so effective that pathogens developed ways to defend against it, and these defenses are a great target for new antivirulence therapies. Gaining a thorough understanding of how NO• interacts with pathogens and how pathogens are able to circumvent NO• stresses will allow for the development of novel therapies that attack a pathogen’s NO• defense system in order to make it more susceptible to NO• damage. This thesis looks to examine how different growth substrates, and their resultant metabolism, contribute to E. coli’s ability to neutralize NO• attack. Understanding how different growth mediums contribute to a cell’s defense network against NO• can potentially elucidate the effect of the intracellular environment on NO• defense. The results of this study show how a growth substrate can directly impact a cell’s NO• defense system. Every assay was run using E. coli WT MG 1655, but the NO• clearance times ranged from 10 minutes to over 4 hours. Pyruvate proved to be the most intriguing growth substrate examined throughout this project, because it was by far the slowest growing cell-culture, but ultimately cleared NO• faster than every other substrate, except the sugars.