GFP fluorescence in different expression system setups. (A) without feedback system (B) WT IbpAB promoter and strong RBS for TetR expression (C) P
promoter mutant m3_2 and strong RBS and (D) P
promoter mutant m4_5 and weak RBS. Cultures were induced with 1 mM IPTG at 2 h. Insets in B-D show that GFP production triggers increased promoter activity for the WT and mutant promoters as indicated by increased RFP reporter expression (for the setup see Figure 2C). GFP expression has been normalized per OD600. Values represent averages +/- standard error of the mean.