FIG. 6.

RhuR is required by B. avium for efficient utilization of hemoglobin as source of nutrient Fe. Fe-stressed cultures of 4169rif, 4169rifbhuR::kan, and 4169rifΔrhuR were used to inoculate 2 ml of BHI broth which was supplemented with 400 μM EDDHA and 300 μM FeSO₄ (High Fe) or with turkey hemoglobin at the indicated concentrations. After 24 h of incubation at 37°C, the OD₆₀₀ of the cultures was measured. Results represent the average cell densities of three cultures. The heme acquisition mutant 4169rifbhuR::kan was used as a negative control (28). Error bars indicate ±1 standard deviation. Asterisks indicate a statistically significant difference from 4169rif (Student's t test).