FIG. 5.
fxbA expression in wild-type and ideR mutant strains. The upstream regulatory region of the C. diphtheriae tox gene and different segments of the fxbA promoter region were cloned into the integrative lacZ reporter vector pSM128. These constructs and the vector were transformed into the wild-type M. smegmatis strain mc2155 and its isogenic ideR mutant derivative SM3. Individual colonies were purified and then grown in LB broth (HI [high iron]) that has repressing levels of iron (30 μM) and also in LB that had been treated with the iron chelator DP to remove Fe (LI [low iron]). Cells were harvested, and β-galactosidase specific activities were determined as described in Materials and Methods. (A) Plasmids containing the promoter −lacZ constructs and schema of their structure. IdeR binding sites are indicated by boxes. Coordinates of the DNA fragments used for the constructions are given in Materials and Methods. Arrows indicate the approximate site of the TSP and direction of transcription. The proximal IdeR box is truncated in pSM354, as indicated in the diagram. (B) Averages of experiments done in triplicate. The β-galactosidase activities of strains containing the promoterless vector pSM 128, less than 3 U in all conditions, were subtracted to give the values presented.