Fig. 3

A model for H₂O₂-dependent and OxyR-mediated transcription regulation of ahpCF and katA2 genes in response to different concentrations of H₂O₂ stress in S. maltophilia. (a) Low-micromolar H₂O₂ is generated by bacterial aerobic metabolism and OxyR is oxidized at a specific “sensing” cysteine residue by H₂O₂. The activated OxyR represses the expression of ahpCF operon and increases the expression of katA2 gene, either directly or indirectly. (b) When bacteria encounter exogenous H₂O₂ stress and the intracellular H₂O₂ concentration increases to millimolar levels, activated OxyR activates the expression of ahpCF operon and katA2 gene, either directly or indirectly