FIG. 2.

Iron-dependent repression of a Fur-regulated promoter by the Fur_Ec and Fur_Dn proteins. The β-galactosidase activity of the fiu-lacZ fusion in E. coli is shown after growth under iron-replete (100 μM FeCl₃; dark gray) and iron-limiting (50 μM Desferal; light gray) conditions. Shown are the fur⁺ (H1698) and fur mutant (H1780) reporter strains, H1780 containing the E. coli (pJIR2281), and D. nodosus (pJIR2300) fur genes on pBluescript SK⁺ and a vector control. Each assay was performed at least four times in four independent experiments. Mean values are displayed with standard deviations as error bars. Asterisks indicate samples that were statistically different (P < 0.05) when grown under iron-replete and iron-limiting conditions.