Grant: Doctoral Research Award: Canada Graduate Scholarships

The threat of antibiotic resistance is one that is growing constantly and new approaches to treat infections are becoming more important. It has been shown previously that bactericidal antibiotics, ones that kill cells instead of inhibiting growth, cause an increase in reactive oxygen species (ROS) as a secondary effect. I have exposed a randomly barcoded mutant library to several ROS inducers/stressors: MS-40, MS-40S, H2O2, As2O3, paraquat, and diamide. My BarSeq analysis has found several processes and genes that are candidates for affecting the levels of ROS inside the bacterial cell, such as purine metabolism, ROS scavenging genes, pyruvate metabolism, and one key pathway is glutathione biosynthesis, which I believe could be a signal for antimicrobial susceptibility. I hypothesize that disrupting the glutathione system with other ROS scavenging pathways, such as purine metabolism or the glyoxylate shunt will lead to an increase in ROS to enhance the activity of bactericidal antibiotics. The induction of antioxidant pathways may be used as markers for antibiotic action. I made a CRISPR interference mutant library, a tool for gene silencing, containing over 85 mutants and will be used to measure ROS levels and furthered characterized to find novel targets for antibiotic adjuvants. In addition, I will use metabolomics to determine the role of antioxidant pathways, especially, glutathione levels, in antibiotic action to be used as a signal. I hope this work will aid in the identification of novel targets to increase antibiotic efficacy and to highlight the important of reactive oxygen species on antibiotic killing.