GidA modulates the expression of catalases at the posttranscriptional level and plays a role in virulence.

, which encodes a putative tRNA-modifying enzyme, is associated with a variety of virulence phenotypes. Here, we demonstrated that is responsible for the modifications of uridine in tRNAs . Loss of was found to have no impact on the mRNA levels of and , but it decreased KatA and KatB protein levels, resulting in decreased total catalase activity and a hydrogen peroxide-sensitive phenotype. Furthermore, was found to affect flagella-mediated motility and biofilm formation; and it was required for the full virulence of in both and macrophage models. Together, these observations reveal the posttranscriptional impact of on the oxidative stress response, highlight the complexity of catalase gene expression regulation, and further support the involvement of in the virulence of .