Fig. 6

Mechanism of action of riboswitches. A (i, ii) Binding of ligand to a riboswitch triggers the formation of a hairpin loop that terminates transcription. A (iii, iv) Binding of ligand to a riboswitch generates the formation of a helix that sequesters the RBS to inhibit the translational process. B (i, ii, iii) Application of riboswitches as biosensors. Riboswitches can be linked to colorimetric reporters (for example GFP) to screen for high-producing strains depending on the concentration of the compound of interest. There is a high expression of the reporter gene when the concentration of a ligand is high (B ii) and vice versa