FIGURE 4.

dksA-deficient Salmonella exhibit a slow turnover of oxidized glutathione. A, redox potentials in wild-type (WT) and dksA mutant Salmonella were calculated according to the Nernst equation factoring NADPH/NADP⁺ intracellular concentrations of stationary phase bacterial cultures. Redox potentials of NADPH, glutathione (GSH), and thioredoxin (Trx) are shown for reference. B, concentrations of reduced GSH and oxidized GSH (GSSG) were quantified in bacterial cultures grown for 18–20 h in LB broth. C, GSH/GSSG ratio is represented. The data are the mean ± S.D. (error bars) of six independent observations from three separate experiments. D and E, recovery of GSH was studied after the bacteria had been exposed to 1 mm H₂O₂ in PBS. 200 units/ml catalase (arrows) were added after 5 min of exposure to H₂O₂. The data are shown as mean GSH/GSSG ratios (D) or total (GSH+GSSG) glutathione (E) from six independent observations collected in three separate experiments. Differences in GSH+GSSG reported in B and E likely reflect growth of the bacteria in LB medium or PBS. F, expression of genes involved in glutathione synthesis was measured as β-galactosidase activity of the indicated transcriptional fusions after the bacteria were grown for 20 h in LB broth. The data are the mean ± S.E. (error bars) of four independent observations from two separate experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001.