Enzymatic antioxidant systems are essential for the survival of aerobic organisms. In bacteria, these systems provide protection against reactive oxygen species (ROS) generated endogenously or from external environmental and host sources. In this project, we will characterize in vivo, in the facultative anaerobic bacterium and environmental pathogen Chromobacterium violaceum, an antioxidant system still little studied, described only in anaerobic purple bacteria. In these bacteria, this system is formed by the hybrid peroxidase (Prx/Grx) GarA and the glutathione amide reductase (GAR) GarB, which act using the low molecular weight thiol glutathione amide (GASH) and NADH to reduce peroxides in vitro. Preliminary data from our group indicate that the garAB genes are induced in the presence of cumene hydroperoxide in C. violaceum. To characterize this system in vivo in C. violaceum, mutant strains will be generated with deletion of the garAB genes, in addition to the respective complemented strains. Phenotypic assays in the presence of various oxidants and virulence assays in mice using these mutant strains, in addition to gene expression assays should reveal whether the GarAB system is important for C. violaceum defense against ROS from different sources. The data obtained in this project should contribute to reveal the importance of the GarAB system in aerobic bacteria and if this system acts on the pathogenesis of C. violaceum.
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