Project Summary Listeria monocytogenes (LM) is the causative agent of listeriosis, a fatal foodborne infection in humans and animals. Invasive form of listeriosis has a mortality rate that ranges from approximately 20%-30% or higher despite antibiotic treatment. Penicillin or ampicillin are reportedly bacteriostatic for LM infections and require effective host defense mechanisms for bacterial clearance. New effective strategies for successful treatment of LM invasive infections are urgently needed. The ability of LM to counteract oxidative stress and reactive oxygen species (ROS) is essential for survival in phagocytic cells and established infection. However, less is known regarding how LM manages or detoxifies ROS encountered during systemic infection. The goal of this proposal is to understand how LM adapts its metabolism and metabolic pathways to alleviate deleterious effects of oxidative stress and adapt to the host environment. The working hypothesis of this application is that FruR alters LM metabolism by shifting metabolic flux from glycolysis to PPP, this metabolic switch is critical for LM’s ability to counteract oxidative stress. This hypothesis will be tested with the following three specific aims: (Aim 1) Explore whether FruR regulates an LM shift from glycolysis to the PPP to combat oxidative stress. In this aim, we will use metabolomics analysis to identify glycolysis and PPP metabolites impacted by FruR upon exposure to oxidative stress. We will also determine the role of FruR in rerouting flux from glycolysis to PPP using 13C-perturbation. (Aim 2) Determine the role of FruR in generating NADPH and protecting against host oxidative burst. In this aim, we will verify if the ΔfruR strain could be complemented by expression of NADPH enzymes. We will investigate the contribution of FruR to LM resistance against ROS produced by the host respiratory burst. (Aim 3) Decipher the role of the oxidative branch of PPP in resistance of LM to oxidative stress via regulation of redox status. In this aim, we will determine the role of two NADPH- producing enzymes in maintaining intracellular redox balance using redox-sensitive green fluorescent protein (GFP) reporter, roGFP2. This study is innovative because it will test a novel mechanism by which LM responds to oxidative stress and host respiratory burst. This mechanism involves upregulation of PPP, focusing on metabolic regulation as a mechanism of LM pathogenesis is a highly innovative approach and could be widespread among other human pathogens. The proposed project is significant because it will (a) delineate the role of FruR on protecting LM from oxidative stress and innate host defenses, (b) provide an opportunity to investigate a new connection between metabolism and virulence, (c) provide a set of metabolic proteins that could be targeted to develop novel therapeutic agents, and (b) enhance understanding of survival mechanisms and oxidative stress response of other intracellular pathogens.

Project Narrative Listeria monocytogenes is the causative agent of listeriosis, a potentially fatal foodborne infection that can affect humans and animals. To survive in host cells and establish infection, L. monocytogenes must be able to withstand oxidative damage caused by reactive oxygen species generated by host oxidative burst. This proposal investigates how L. monocytogenes adapts its metabolic pathways to combat oxidative stress to enable future development of better treatment options.