FIG. 3.

Promoter activities as a function of growth rate. β-Galactosidase activities were measured at different growth rates, obtained by growing cells in different media as described in Materials and Methods: M9 medium with 0.4% glycerol, M9 medium with 0.4% glucose, M9 medium with 0.4% glycerol plus 0.8% Casamino Acids plus tryptophan, M9 medium with 0.4% glucose plus 0.8% Casamino Acids plus tryptophan, and LB medium. Linear regressions were drawn by using SigmaPlot 5.0 (Jandel Scientific). The endpoints of the wild-type and mutant rrnB P2 promoter fragments used to construct the fusions are indicated in the panels. The lacUV5 promoter-lacZ fusion shown in panel E has been described previously (12). To enable visual comparison of the slopes, the activity of each promoter was normalized to a value of 1.0 at a growth rate of 0.9 doubling per hour (8). Strain designations and observed promoter activities (in Miller units) at a growth rate of 0.9 doubling per hour are as follows: A, RLG3851, 784 ± 34 U; B, RLG3863, 1,749 ± 72 U; C, RLG5014, 1,958 ± 236 U; D, RLG3914, 4,189 ± 252 U; E, RLG4993, 408 ± 66 U; F, RLG3915, 7,211 ± 300 U; G, RLG3898, 3,167 ± 281 U; H, RLG3897, 2,240 ± 104 U. Data from at least two independent experiments are shown for each construct.