Level of stress proteins after production of α-glucosidase at different temperatures. Cultures were grown to an OD600 of 0.5 at 37°C, induced with 1 mM IPTG and transferred to the indicated temperatures for two hours. After two-dimensional gel electrophoresis of the proteomes, spot volumes quantified by densitometry of Coomassie-stained gels were normalised with the summed volumes of three reference spots marked in Fig. 2 by circles. Concentrations c in the wildtype strain with ibpAB overexpression (black bar), without overexpression (grey bar), and in the ibpAB deletion mutant (white bar) are given relative to the maximum concentration cmax determined for the respective protein to facilitate comparison. The 95% confidence interval from four experiments at 42°C are shown. Protein designation are given above the panels: chaperones DnaK and ClpB, the thermo-unstable elongation factor (EF-Tu), enolase (Eno), polynucleotide phosphorylase (PNP), and glyceraldehyde 3-phosphate dehydrogenase (GAPDH). Production temperatures are given below the bars.