FIG. 1.

Fur-dependent regulation of bhuR::phoA in B. avium Pho20. A fur knockout in Pho20 was engineered by integration of ptr5-1 (29) into the fur gene of Pho20. Pho20 and Pho20(fur) were cultured in Fe-replete and Fe-stressed BHI broth. Expression of the bhuR::phoA reporter in each strain was determined by measuring alkaline phosphatase activity using a colorimetric assay (35). Activity is reported as micromoles of NPP hydrolyzed per minute per OD₆₀₀ unit. The mean ± 1 standard deviation from the mean (indicated by the error bar) is shown for each value. Asterisks indicate that the Pho20(fur) values are significantly different (P < 0.05) from the values for Pho20 cultured under identical conditions, as determined by the Student t test.