Fig. 2.
Effect of chaperone overexpression on σ32-dependent transcription in the chromosomal σ32 mutants. WT and σ32 mutants carrying the PhtpG-lacZ reporter and either Para-groESL (Left) or PA1/lacO-1-dnaKJ (Right) on the chromosome were grown at 30°C in LB medium containing, respectively, 0.2% arabinose or 5 μM IPTG to maintain normal chaperone levels. (A–C) GroEL/S was overexpressed from pGro11 by addition of 25 ng/ml anhydrotetracycline. (D–F) DnaK/J was overexpressed by addition of 1 mM IPTG. ●, control cultures; ▲, chaperone overexpression cultures. Arrows, time of induction. Western blots taken at the last time point indicated an ≈5- to 8-fold increase in GroEL and ≈4- to 5-fold increase in DnaK.