Figure 1.

The biosensor transfer function and design. (a) The transfer function of a biosensor enables the quantitative characterisation of biosensors showing the correlation between input effector concentration and the biosensor output. Transfer functions thereby provide information on product sensitivity, the operational range of detection and the dynamic output range as defined by the difference between minimum (OFF) and maximum (ON) biosensor outputs. (b) Expression of the allosterically regulated transcriptional repressor TrpR_Rep controls the expression of a gene of interest (GOI) by tryptophan-dependent binding to the promoter harbouring four TrpR binding sites (4xtrpO). To the right a schematic transfer function of TrpR output in relation to tryptophan concentration is illustrated. (c) Expression of the allosterically regulated transcriptional activator BenM_Act controls the expression of a GOI by cis,cis-muconic acid-dependent binding to the promoter harbouring three BenM binding sites (3xbenO). To the right a schematic transfer function of BenM output in relation to cis,cis-muconic concentration is illustrated. AU; arbitrary units.