Fig. 1: Evaluating temperature-sensitive transcriptional repressors in E. coli Nissle 1917.

a Illustration of the genetic circuit used to characterize the behavior of temperature-sensitive repressors in E. coli Nissle 1917. b Optical density (OD₆₀₀)-normalized fluorescence as a function of induction temperature for a fixed duration of 1 h, measured 24 h after induction. Error bars represent ±SEM. To confirm that the resulting data is not driven by temperature driven changes to OD, wildtype EcN were similarly analyzed and displayed no temperature dependent fold change. Additionally, total cell count by flow cytometry was also used as a proxy for cell number and generated similar results to the ones collected by normalizing through OD as a proxy for cell count (Supplementary Fig. 1). c OD-normalized fluorescence 24 h after a 1-hour induction at 37 °C or 42 °C for the constructs shown in (b). Measurements with values below the bottom of the y-axis appear below the axis. Bars indicate the mean. Vertical lines indicate the difference between the 42 °C and 37 °C conditions. Numbers indicate fold-change. d OD-normalized fluorescence as a function of induction duration. Cells were stimulated at 42 °C and fluorescence measured 24 h later. e Illustration of the pulsatile heating scheme used to optimize thermal induction and cell viability. f OD-normalized fluorescence as a function of pulse duration for the TcI₄₂ circuit. All samples were stimulated for a total of 1 h at 42 °C and 1 h at 37 °C and evaluated 24 h later. Viable cell counts at various pulse durations plotted to reflect cell viability. Where not seen, error bars (±SEM) are smaller than the symbol. n = [5, 5, 6, 4] biologically independent replicates for panels [b, c, d, f]. All source data are provided as a Source Data file.