Figure 5.

The Escherichia coli-based ex vivo reporter assay system using luciferase. (A) RpoD and FliA expression levels. RpoD and FliA protein levels in E. coli cells were analyzed by SDS-PAGE with or without IPTG treatment. Protein extracted from equivalent cell numbers were loaded onto each lane representing each experimental time point (0–1.5 h). Below each lane, the “-fold” numbers represent protein band density from each IPTG+ lane subtracted by the density calculated from the respective IPTG- lane, and then normalized to the density value at 0 h. (B) Luciferase activity measurements of σ factors regulating different promoters. Relative light unit (RLU) values indicate the magnitude of luciferase activity. RLU readings were normalized according to cell density (OD₆₀₀). Closed and open symbols (circle and triangle) indicate treatment with or without IPTG, respectively. Error bars indicate SE. * and **Statistically significant differences at P < 0.05 and P < 0.01, respectively (Student's t-test).