FIG 2 .

Rifampin resistance mutations in rpoB reduce transcriptional efficiency. (A) The graph shows an example of how luciferase (lux) reporter activity was determined in an rpoB mutant strain (H531R) relative to the reporter activity in the ancestral strain. The IPTG-induced luminescence emissions (RLU) per optical density (OD₆₀₀) were monitored continuously, and the maximal gradients on the RLU/OD₆₀₀ curves during early exponential phase were calculated (dotted lines). The absolute lux reporter activity in each of the rpoB mutants was normalized to that of the ancestral strain control within each assay to obtain relative lux reporter activity, which is used as a proxy for relative transcriptional efficiency measurements. (B) lux reporter activities in rpoB mutants relative to that in the rifampin-sensitive ancestral strain (mean ± SE; n = 3), which are used as estimates for relative transcriptional efficiency. All mutations except S536F resulted in significant reductions in the relative transcriptional efficiencies of rpoB mutants, as determined by Dunnett’s test (*, P < 0.05).