FIG. 5.

In vivo expression from wild-type or mutant fnr′-lacZ (−155 to +25) promoter fusions from anaerobically (A) or aerobically (B) grown cells measured using β-galactosidase assays. FNR⁺ and FNR⁻ strains are represented by the white and gray bars, respectively. “−” indicates that base substitutions (Fig. 1) were made within the predicted upstream FNR binding site, the predicted downstream FNR binding site, or both sites. “+” indicates that the wild-type sequence is present. β-Galactosidase activity from the fnr′-lacZ promoter fusions was normalized by correcting for the difference in cell numbers ml⁻¹ of culture for aerobically and anaerobically grown cells as explained in Materials and Methods. Error bars represent the standard errors for three independent experiments.