FIG 7.

Siderophore production is negatively regulated by Fur. The production of siderophores was detected using colorimetric CAS agar plates (32). For each strain, inoculum was taken from a single colony grown on nutrient agar and streaked down the middle of the CAS plates, followed by incubation for 10 days at 28°C. The halo radius was measured at its widest point from the edge of the colony growth. The graph represents the mean halo radius from 15 plates. Bars with different letters indicate significance based on a Student t test using P ≤ 0.05. Error bars indicate the standard errors of the mean.