Figure 4. The absence of a functional speG gene in Shigella increases survival to the oxidative stress.

Effect of hydrogen peroxide on S. flexneri wild type strain M90T (top left), on its speE-defective derivative M90TEd (top right) and on M90T complemented with the entire ynfB-speG operon (plasmid pULS37, bottom right) or only the speG gene (plasmid pULS55, bottom left). A clear difference can be appreciated in the halo of inhibition around the paper disk soaked with 5 µl of H₂O₂ 30 w.t. % sol. in water (Sigma-Aldrich); sectors of four agar plates are shown at the same enlargement.