FIG. 3.

Effect of iron levels on expression of bfr, bfrα, and bfrβ. DLR strains SCH115 (fes-fepA-fluc; bfrα::rluc), SCH119 (fes-fepA-fluc; bfr::rluc), and SCH121 (fes-fepA-fluc; bfrβ::rluc) were cultured in iron-replete (15 μM of iron) and iron-depleted medium (200 μM of 2,2′-dipyridyl) for 48 h and then analyzed by the dual luciferase assay. Values are expressed as the level of luciferase activity measured under treatments with low levels of iron divided by that from cells cultured in the presence of high levels of iron. The solid and open bars represent firefly and Renilla luciferase activity, respectively. Values are means of data from triplicate cultures (with standard deviation).