Iron availability modulates the transcription of clbA. Growth curves (OD600) and the RLU/OD600 of Nissle 1917 clbA-lux (A), clbB-lux (B), clbQ-lux (C), and clbR-lux (D) fusion strains grown at 37°C in DMEM-HEPES, DMEM-HEPES supplemented with 40 μM 8-HQ, or DMEM-HEPES supplemented with 100 μM FeCl3. (E) AUC, determined with GraphPad Prism (version 6.0) software, of the RLU/OD600 of clbA under the three different conditions. The given values are the mean number of RLU and SEMs from five independent experiments. Statistical analysis was performed using two-way ANOVA and the Bonferroni posttest. ***, P < 0.001 compared to the mean values obtained in DMEM-HEPES.