TABLE 4.

Transcriptional analysis of promoter-lacZ fusions in C. diphtheriae strains under high- and low-iron conditions

Promoter fusionbβ-Galactosidase activity unitsa
C7(−) (dtxR+)1737 (dtxR+)C7(β)hm723 (dtxR)
+Fec−FeRatio (−/+)+Fe−FeRatio (−/+)+Fe−FeRatio (−/+)
pciuEP-lacZ1.721.612.70.716.623.710.230.53.0
pciuAP-lacZ27.4100.03.65.9179.330.4106.0165.21.6
ptox-lacZ0.7139.4199.10.580.1160.238.1153.54.0
  • a β-Galactosidase units were determined as described previously (34). Values are the means of three experiments, and results from each assay varied by less than 25% from the mean.

  • b DNA fragments containing the 1737 ciuE and ciuA upstream regions were assessed for promoter activity in pCM502.

  • c +Fe, PGTH medium with 5 μM FeSO4; −Fe, unsupplemented PGTH medium.