Figure 3
Schematic of tetracycline sensor coupled to the positive-feedback amplifier. The one-component tetracycline sensor consists of a plasmid where LuxRΔ2-162 has been cloned behind the TetR-regulated P LtetO-1 promoter. In the absence of the inducer anhydrotetracycline (aTc), dimeric TetR binds to the O2 operator sites within the P LtetO-1 promoter and represses transcription. However, when bound with aTc, TetR is no longer able to bind to the O2 operator sites within the promoter, thus enabling dose-dependent control of LuxRΔ2-162. This sensor was coupled with the positive feedback amplifier, encoded on a separate plasmid, by transforming cells (GN100) constitutively expressing a chromosomal copy of the tetR gene with the two plasmids respectively harboring the sensor and amplifier.