FIG 4.
Comparison of riboswitch regulation, IPTG induction, and a hybrid regulatory system in S. elongatus PCC 7942. Reporter strains containing Ptrc driving expression of YFP were cloned with and without the lacIq repressor gene and with and without riboswitch F. Strains were induced with 1 mM IPTG (A), 2 mM theophylline (theo) (B), or 1 mM IPTG and 2 mM theophylline (C) (closed circles), and uninduced control cultures were treated with 1% DMSO (open circles). After induction for 1 day, cultures were normalized by OD750 and YFP expression was quantified with a fluorescence plate reader (scale on the right). The values shown are averages of three biological replicates ± the standard deviations. Gray columns depict induction ratios calculated by dividing induced values by uninduced values (scale on the left). n/a, not applicable.