Investigating Hydrogen Peroxide Metabolism in the Absence of the Major Detoxification Systems

Abstract

Hydrogen peroxide, H\(_{2}\)O\(_{2}\), is a key source of oxidative stress in living cells and can cause extensive damage to cells, especially DNA damage. If left unchecked, this oxidative stress can ultimately prove fatal. Because most cells naturally produce hydrogen peroxide and other reactive oxygen species (ROS) as byproducts of aerobic metabolism, they have developed natural defenses in the form of H\(_{2}\)O\(_{2}\)-scavenging enzymes and biomolecules. In Escherichia coli, two catalases and alkyl hydroperoxide reductase are responsible for the majority of H\(_{2}\)O\(_{2}\) detoxification. The Hpx- strain, however, lacks the genes that codes for these enzymes and therefore is incapable of detoxifying endogenous H\(_{2}\)O\(_{2}\). In this project, we explored alternative methods by which Hpx- could detoxify endogenous H\(_{2}\)O\(_{2}\) and restore normal growth. Our attempts at transposon mutagenesis did not produce such a mutant. Natural adaptation produced two promising populations with improvements in growth rate, implying a corresponding improvement in detoxification ability, but the exact nature of their growth improvement is still to be determined. Further work is necessary to determine the nature of the developed growth advantage and to characterize the responses of these two adapted populations to oxidative stress.