Fig. 2: QUAS spacing upstream of the T7 promoter.

a Schematic depicting QUAS (orange square with lines) spaced 5 base pairs upstream of the T7 promoter (QUAS-5-T7) driving the expression of GFP (green) (top) and the effect of QF (orange) on GFP expression (bottom). In the absence of QF, the transcription of GFP is not initiated. When QF is present, (QUAS-5-T7 + QF) it binds to QUAS and activates the transcription of GFP. Flow cytometry quantifying GFP fluorescence over a 10-h period after the initial induction of 0.5 mM IPTG (added at time zero) to initiate the transcription of T7RNAP without QUAS (purple), with QUAS 5 base pairs upstream of the T7 promoter in the absence (blue), and presence (green) of QF. A two-tailed t-test was performed to determine statistical significance (P < 0.02) between the T7 control and components of the Q system with QUAS placed 5 base pairs upstream of the T7 promoter. An aster (*) represents statistical significance. b Schematic depicting QUAS (orange square with lines) spaced 10 base pairs upstream of the T7 promoter (QUAS-10-T7) driving the expression of GFP (green) (top) and the effect of QF (orange) on GFP expression (bottom). In the absence of QF the transcription of GFP is not initiated, however, in the presence of QF (QUAS-10-TF + QF) it binds to QUAS and activates the transcription of GFP. Flow cytometry quantifying GFP fluorescence over a 10-h period after the initial induction of 0.5 mM IPTG (added at time zero) to initiate the transcription of T7RNAP without QUAS (purple), with QUAS 10 base pairs upstream of the T7 promoter in the absence (blue) and presence (green) of QF. A two-tailed t-test was performed to determine statistical significance (P < 0.002) between the T7 control and components of the Q system with QUAS placed 10 base pairs upstream of the T7 promoter. An aster (*) represents statistical significance. c Schematic depicting QUAS (orange square with lines) spaced 15 base pairs upstream of the T7 promoter (QUAS-15-T7) driving the expression of GFP (green) (top) and the effect of QF (orange) on GFP expression (bottom). In the absence of QF the transcription of GFP is not initiated. When QF is present, (QUAS-15-T7 + QF) it binds to QUAS and activates the transcription of GFP. Flow cytometry quantifying GFP fluorescence over a 10-h period after the initial induction of 0.5 mM IPTG (added at time zero) to initiate the transcription of T7RNAP without QUAS (purple), with QUAS 15 base pairs upstream of the T7 promoter in the absence (blue), and presence (green) of QF. A two-tailed t-test was performed to determine statistical significance (P < 0.007) between the T7 control and components of the Q system with QUAS placed 15 base pairs upstream of the T7 promoter. An aster (*) represents statistical significance. Each experiment consisted of generating data from at least three separate bacterial colonies grown in overnight cultures, where circles represent individual data points in the plots. These experiments were repeated independently at least three times with similar results. The geometric mean of each sample was calculated via FlowJo, and error bars indicate standard deviation. Fluorescence values were normalized to the T7 control (purple) expression at 1 h. The error bars indicate 95% confidence intervals of the mean of fluorescence, and data are presented as mean ± standard deviation. Source data are available as a Source data file.