Masters Thesis

Characterization of gor in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is an opportunistic pathogen that commonly causes serious nosocomial infections. P. aeruginosa’s virulence is derived from its large genome that allows adaptations to many environments and high antibiotic resistance. Gene sequences and pathways linked to bacterial survival or virulence need to be characterized before being chosen for therapeutic targeting to combat infections. One such set of genes are those leading to the production or activity of glutathione (GSH). GSH is a low molecular weight thiol that P. aeruginosa produces as a redox buffer that significantly contributes to its virulence. Previous studies have shown that P. aeruginosa transposon mutants defective in gshA (the first step of the glutathione pathway) have decreased virulence and increased susceptibility to thiol-reactive antibiotics. Genes encoding glutathione reductase (gor) are another possible target to stunt the P. aeruginosa oxidative stress response. The Gor enzyme maintains cellular redox homeostasis which resists oxidative stress. We obtained a transposon mutant disrupting gor (gor::tn) and generated a gor complement strain (MCgor) in the transposon background. When compared to P. aeruginosa wild type (MPAO1) and MCgor, gor::tn had similar growth and swarming motility capabilities, greater sensitivity to oxidative stressors, and decreased biofilm, pyocyanin, and persister cell production. Surprisingly, gor::tn outcompeted Staphylococcus aureus to a greater extent than MPAO1 did in mixed species competition assays. These comparisons are beneficial to the characterization of gor and add further support to develop antibiotics targeting the glutathione pathway.