FIGURE 3.
A double fluoride riboswitch construct with PS7 is strongly repressed and inducible. Total luciferase activity in cultures was calculated over an incubation period of a few hours, ∼ 7 h for E. coli DH5α and 5 h for B. thailandensis, these time points were selected because they were above background, as expression remained low even when induced (Supplementary Figure S6). Both were transformed with the B. thailandensis E264 fluoride riboswitch construct which has an additional fluoride riboswitch from Nitrosomonas europea upstream (pVK-2f2-lux). The plasmid is replicative in E. coli strains and integrative in B. thailandensis E264. Both pre-culture media (LB) and expression media (0.5X M9-MM) were supplemented with appropriate antibiotics depending on the species (see Methods). Fluoride induction concentrations are as indicated. Concentrations were chosen according to the maximum induction effect. The values for each sample represent the means and standard deviations of triplicates on the same microplate.