Fig 4. Box plot analysis depicting cell-to-cell variations in gene expression for different optimally induced E. coli expression systems.
Cell-to-cell fluorescence distributions of optimally induced expression systems are depicted with the total mean (dotted red line) and the spread interval (25% of mean, grey box) for ten individual microcolonies evaluated at the end of each experiment (end point criteria: cultivation chambers fully filled with cells or μmax ~ 0). Exact inducer concentrations for optimal induction were 0.1 mM IPTG (for each system), 1 mM galactose, 1 mM arabinose, 0.1 mM m-toluic acid and 1.5 mM salicylic acid. For each individual colony, medians (bold red line) indicate values above which 50% of cells are located, blue boxes indicate interval into which 50% of fluorescence values fall. Top or bottom of the box show areas, where 25% of cells are located above or below, respectively. Antenna indicate the 1.5-fold interquartile distance (IQR, 1 IQR = box height) or the last data point detected inside the 1.5-fold IQR. Outliers outside of the 1.5-fold IQR were marked as crosses.