Infection of HeLa cells followed by indirect assessment of colibactin expression via quantification of phosphorylated histone γ-H2AX indicated that clbR overexpression in E. coli strain M1/5 led to a strong increase of γ-H2AX levels, whereas γ-H2AX levels were markedly decreased in the clbR deletion mutant relative to the wild-type strain (Fig. 8B). The gene discussed is H2AX; the disease is infection.