FIG 2.

Deletion of the spermidine synthase SpeE impacts full genotoxicity of colibactin-producing E. coli. The production of colibactin by E. coli strain DH10B pks⁺ and derivatives was determined by quantification of H2AX phosphorylation, which correlates with DNA damage resulting from the genotoxic effect of colibactin. E. coli strain DH10B pks⁺, the ΔclbA mutant (negative control), and the ΔspeE mutant and its complemented derivative were cocultivated with HeLa cells in an In-Cell Western assay as previously described (35). The multiplicity of infection (MOI [i.e., the number of bacteria per cell) ranged from 100 to 400. Data shown in the graph are representative of three independent experiments. All bar graphs show mean values ± SEM.