FIG. 5.

Effects of a stringent rpoB allele on iraD transcription and RpoS levels. (A) iraD::luxCDABE expression from a −600 to −1 fusion construct in a “stringent” RNA polymerase mutant. Each data point is an average of three independent determinations. Wild-type and rpoB* represent iraD::luxCDABE expression in the MG1655 and the rpoB* strains, respectively. The variability is shown with error bars in both graphs. RLU, relative luminescence units (bioluminescence counts per minute, normalized to the OD₆₀₀). (B) Steady-state RpoS levels in MG1655 (Ctrl), rpoB*, and rpoB* iraD double-mutant strains at a growth phase corresponding to an OD₆₀₀ of 0.3. (C) RpoS stability in the same strains at the same growth stage, following chloramphenicol treatment to block new protein synthesis. Levels of RpoS are shown at times indicated after chloramphenicol treatment. (D and E) Luciferase expression from promoter fusions to P1 (−600 to −375) (D) or P2 (−262 to −1) of the iraD upstream region (E). The data represent averages of at least three determinations.