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. 2010 Nov 9;39(3):e12. doi: 10.1093/nar/gkq1070

Figure 3.

Figure 3.

Plasmid-born model circuits function as AHL/GFPUV inverters. Logic diagram (A), plasmid constructs (B), and the actual behaviors (C) of the AHL/GFPUV inverter circuits. Plasmid-A constitutively expresses LuxR, which activates the CI repressor in the presence of AHL. CI represses GFPUV on pCI-gfpUV, which is under the control of the PL promoter. Overall, the level of GFPUV output is the inverse of the input signal, AHL. Plasmid-B also produces an AHL/GFPUV inverter, but it has a partial truncation of the CI repressor, requiring a higher concentration of AHL to fully switch off the output (GFPUV fluorescence). Plasmid-C lacks translational signals for CI, resulting in an always ON phenotype. Plasmid-D lacks the transcriptional terminator downstream of the LuxR, which results in the constitutive repression of GFPUV (always OFF). The semicircles and the hairpins indicate the ribosome-binding sites and transcription terminators, respectively. (C) The cell pellets of Strains containing Plasmid-B, -C, or -D together with pCI-gfpUV after 12 h of incubation in the presence of various concentrations of AHL.