Figure 4

Fluorescence images capturing the effect of the hyper-osmotic stress on the expression of GFP through the lacZ operon. (a) GFP expression in cells grown on glycerol in the absence of salt. (b) GFP expression in cells grown on glycerol in the absence of salt and later exposed to 1.5 mol l⁻¹ salt concentration. No significant decrease in the intensity was observed compared to Figure 1a reflecting that GFP activity is not degraded. (c) GFP expression in cells grown on glycerol with 1.5 mol l⁻¹salt concentration. GFP expression seems to decrease indicating strong inhibitory effect of salt on lac operon induction. (d) GFP expression in cells grown on glycerol in the absence of IPTG and salt (control experiment). GFP is not expressed at all in the absence of inducer (IPTG). Note that Figure 1a, b and c were obtained by providing saturating amount of IPTG (200 μmol l⁻¹) in the medium. The corresponding bright field image is shown on right side of each condition showing similar number of cells for each case.