<i>Bacillus</i> spp. Antibacterial Activity Induced by Triphenyl Tetrazolium Chloride against <i>Ralstonia solanacearum</i>: Oxidative Stress Response and Metabolome Changes

High salt concentrations affect the electron transport chain of bacterial cells, leading to an oxidative stress response that encompasses the formation of reactive oxygen species (ROS). The salt 2,3,5-triphenyltetrazolium chloride (TTC) triggers antibacterial activity against the phytopathogen <i>Ralstonia solanacearum</i> in <i>Bacillus</i> species; however, the underlying mechanisms remain unknown. Here, we tested the hypothesis that TTC-inducible activity is related to the formation of ROS and its metabolites. We found that l-ascorbic acid, superoxide dismutase, and catalase counteracted TTC-inducible activity in various <i>Bacillus</i> species. Furthermore, <i>R. solanacearum</i> exhibited a higher susceptibility to H₂O₂ than <i>Bacillus</i> spp. Genomic analysis showed differences in stress-related genes, with <i>Bacillus</i> strains containing the ROS scavengers bacillithiol and bacillibactin, while glutathione in<i>R. solanacearum</i>. Multivariate analysis indicated that the <i>Bacillus</i> species and TTC influence <i>Bacillus</i> metabolome, resulting in higher levels of quinazoline alkaloids, with potential antibacterial activity against <i>R. solanacearum</i>. Results suggest that TTC induces the production of O₂^•- and H₂O₂ and metabolites that arrest <i>R. solanacearum</i> growth.