FIGURE 5.

Inducer-dependent orthogonality of the diacetyl-inducible sensors. The response of L. lactis sensor strains Pdar-gfp and Pusp45-gfp to diacetyl, acetoin and 2,3-butanediol (A), diacetyl degradation pathway in L. lactis. The enzymes involved in diacetyl degradation include acetoin (diacetyl) reductase (dar), acetoin reductase (butA) and 2,3-butanediol dehydrogenase (butB) (B,C), Dose response curves of the sensor strains, illustrating the correlation between inducer concentration and fluorescence output. Population-level normalized GFP expression (RFU/OD₆₀₀) of bacterial cultures, Pdar-gfp (B), and Pusp45-gfp (C) strains, in CDM with increasing concentration of diacetyl (1.2 to 4.6 mM; plots at the top), acetoin (0.1 to 0.45 M; plots in the middle), and 2,3 -butanediol (0.2 to 0.9 mM; plots at the bottom). The compounds were added at time zero. Dots represent the average values of independent experiments (n = 3). Error bars represent standard deviation (SD) of the mean values of the three independent experiments.