Fig. 1

Exogenous addition of HSL induces the expression of temporally regulated cascade circuits. a Pattern diagram of the cascade circuits of exogenously induced expression. The hybrid promoter P_tra* was created by replacing the lux-box in the commonly used P_luxI promoter with the tra-box, which improves the inducibility of the Tra system [29]. b Normalized characterization curves for 3OC8HSL-induced Las, Tra system circuits. c Normalized characterization curves for 3OC12HSL-induced Las, Tra system circuits. d Normalized characterization curves for 3OC6HSL-induced Lux, Tra system circuits. e Normalized characterization curves for 3OC8HSL-induced Lux, Tra system circuits. f Normalized characterization curves for 3OC12HSL-induced Lux, Tra system circuits. To study the time interval between GFP fluorescent protein and RFP fluorescent protein expression in the regulatory circuit more intuitively and clearly, the fluorescence intensity of GFP and RFP after characterization was normalized, that is, the maximum value of each characterization curve was normalized. When the vertical coordinate of the characterization curve is 0.5, the value corresponding to the curve on the x-axis is the response time of the fluorescent protein [32, 33]