FIG 6.

Mutational analysis defines regulatory element nucleotides required for PmrA-driven expression. (A) Regions upstream of pmrA-regulated cbu0021 and the CoxigA gene. Boldface nucleotides show mutational changes of the two TTAA regions within the predicted PmrA regulatory element (MUT1 and MUT2), while underlined nucleotides show mutational changes within the −10 promoter region (MUT3). (B) Luciferase activity of wild-type (WT) C. burnetii expressing transcriptional proteins of the lux operon fused to nonmutated promoter regions or regions containing the MUT1, MUT2, or MUT3 mutation. Luciferase activity was also assessed for the ΔpmrA mutant expressing lux fused to nonmutated promoters and wild-type C. burnetii and the ΔpmrA mutant expressing lux alone. Assays were conducted after 4 days of growth in axenic medium. Bioluminescent readings are expressed as relative light units (RLU). Results are expressed as the means of results from two biological replicates from three independent experiments. Error bars indicate the standard deviations from the means, and asterisks indicate a statistically significant difference (P < 0.0001) with respect to wild-type C. burnetii expressing a nonmutated promoter lux fusion.