FIG 7.

Spermidine is involved in colibactin biosynthesis. The colibactin prodrug motif N-myristoyl-d-asparagine, produced by the wild-type (WT) E. coli strain DH10B pks⁺, the ΔclbA and ΔspeE mutants, and the complemented derivative, was quantified by liquid chromatography-mass spectrometry (LC-MS). Bacteria were cultivated at 37°C for 18h in DMEM-HEPES, supplemented when indicated with 20 μg/ml of spermidine, and the levels of bacterial growth were similar under all conditions. The data presented in the graph were obtained from four biological replicates. ***, P < 0.001, and **, P < 0.01, by 1-way ANOVA. All bar graphs show mean values ± SEM.