Oxidative Stress in Shiga Toxin Production by Enterohemorrhagic Escherichia coli

Figure 4

A model for OxyR-mediated modulation of lambdoid prophage maintenance under normal growth conditions and oxidative stress. Under normal growth conditions (a), the OxyR protein is inactive. The cI protein binds to and operators, repressing and stimulating . At high concentrations, cI binds also to which caused repression of . Under oxidative stress conditions (b), OxyR is activated and binds to the region. This stimulates binding of cI to and , enhancing repression and stimulation, and when cI concentration increases, repression is prevented by competitive binding to by OxyR. This results in higher activity of than that under normal growth conditions, increased levels of cI, and more efficient maintenance of the prophage.

(a) Normal growth conditions

(b) Oxidative stress conditions