Fig. 1
sasA exhibits cell-to-cell variability in expression. a PsasA-yfp expression in log phase culture. Left: YFP image. Color scale indicates the fold change relative to the population average. Right: Phase contrast. Scale bar indicates 10 µm. b Schematic of the dual-color transcriptional reporter strain used to characterize the noise in sasA expression. Two copies of the sasA promoter driving different reporters (PsasA-yfp, PsasA-mcherry) are inserted at separate ectopic loci. c Evidence for extrinsic noise in sasA expression. Images of single cells from the dual reporter strain with significant fluorescence shown in mCherry (Left), YFP (Center), and phase contrast (Right) channels. Scale bar indicates 5 µm. d Quantification of cellular fluorescence intensities for single cells in the experiment described in b, c. Values were normalized relative to the population mean value for each channel. Data shown was measured on ~580 cells with detectable fluorescence in both channels. The fluorescence of the two reporters have a Pearson’s correlation coefficient of r ~ 0.90 ± 0.08 (mean ± SEM, 4 experiments). For each reporter, the CV ~ 4.95 ± 0.42 (mean ± SEM, 4 experiments)
