Figure 4.

(a) Formation of the pyomelanin pigment was observed for E. coli HPD. Adding one of the prototypical β-triketone inhibitors decreased pyomelanin formation in a dose-dependent manner with increasing inhibitor concentrations (shown for sulcotrione 0–5 µM). The EV obtained an OD₄₀₅ (OD_405-EV) of 0.38 ± 0.04 and was used as a negative control. (b) The percentage of inhibition was calculated following Eq. 1 and Eq. 2. The calibration curves for the β-triketone inhibitors were fitted by the sigmoidal logistic four-parameter equations. (c) The IC₅₀ values calculated for each of the HPD inhibitors were 0.396 ± 0.048 µM (mesotrione), 0.244 ± 0.071 µM (nitisinone), 0.187 ± 0.037 µM (sulcotrione) and 0.610 ± 0.015 µM (tembotrione).