Figure 1.

Effects of streptomycin on total carbonyl content (□) and GroEL production (●) in E. coli MG1655. Cells were treated with streptomycin concentrations ranging from 0.01 to 1 μg/ml, which have no effect on growth rate (data not shown), and crude extracts were used for carbonyl content quantification (7). In the same samples, GroEL levels were determined by Western blot analysis using monoclonal mouse anti-GroEL antibodies. Quantification of carbonyl and GroEL levels were obtained using the ImageQuant software (Molecular Dynamics). The carbonyl and GroEL levels in the nontreated controls were assigned a value of 1.0. The relative rates of SodA (black bars), KatE (open bars), Dps (gray bars), and GorA (hatched bars) production in nontreated and streptomycin-treated cells were determined as described (7). Sod and Kat activity was determined and expressed as described in Materials and Methods and the extent of disulfide bond formation (ΔAP activity) was as described in refs. 7 and 22. The analysis was repeated three times to confirm reproducibility. Representative results are presented and the SD was always <20% between experiments.