Previous studies showed that several representative bacterial thiol-based redox-sensing proteins (VirA, OxyR, DksA, SpxA1, QsrA, OhrR/2-Cys, Spx, YodB, CrtJ, and CprK) regulate gene expression and play important roles during infection (Antelmann and Helmann, 2011; Wong et al., 2015). Here, SPX is linked to infection.