FIG. 9.

Analysis of bfr gene expression in E. chrysanthemi. (A) bfr messenger accumulation in the wild-type (WT) strain and the ΔryhB mutant. Cells were grown in L broth until an OD₆₀₀ of 0.9 was reached, and 20 μM FeSO₄ was added. Samples were collected every 20 min, and Northern experiments were carried out as described in Materials and Methods. (B) Expression of a transcriptional bfr::uidA fusion during bacterial growth. Cells were grown in L medium. FeSO₄ (20 μM) was added at an OD₆₀₀ of 0.4. Samples were collected after the addition of iron as indicated. β-Glucuronidase activity was determined as described in Materials and Methods. White bars, with iron; black bars, no iron. Experiments were performed in triplicate, and standard deviations are shown.