β-Galactosidase assays of the 5′-UTR–bgaB fusions. (A) The used inducible reporter plasmid with the candidate thermometer placed directly upstream of the thermal stable β-galactosidase gene (bgaB) along with a schematic of bgaB fusions. (B) The activity of the tetR thermometer is expressed in Miller units. The 5′-UTR–bgaB fusions were incubated at 25°C, 37°C, and 42°C in triplicates, and their absorbances were measured to determine the expression of bgaB at each temperature. The Miller units were calculated for all 5′-UTR–bgaB fusions using the absorbances, and can be seen in Supplemental Figure S2. (C) Heat induction profiles for 5′-UTR–bgaB fusions, with the expressions at 25°C, 37°C, and 42°C compared to a positive control, the blyA fourU thermometer, and a negative control, DNA gyrase (gyrA). (D) Heat induction profiles of the mutated RNA thermometers. The heat inductions of the UU2930CC tetR and the UU2122CC σ70 mutants were calculated, and compared to the blyA positive control and gyrA negative control.
