FIGURE 3.

DksA-mediated control of central metabolism boosts cellular reductive power and resistance to H₂O₂. A, expression of key dehydrogenases associated with generation of reduced pyridine nucleotides in the pentose phosphate pathway (yellow), glycolysis (blue), or the tricarboxylic acid cycle (green) was evaluated by following lacZY transcriptional activity of the indicated genes. Transcriptional activity was measured in wild-type (WT) Salmonella or dksA mutant bacteria grown for 20 h in LB broth. The data represent the ratio of β-galactosidase activity supported by the mutant bacteria over WT. Genes expressed 2-fold or lower in the absence of dksA are shown in bold. The data are the mean of four to nine independent observations from at least two separate experiments. B and C, NAD(P)⁺ and NAD(P)H pyridine nucleotides were measured in strains bearing mutations in genes shown to be differentially regulated by DksA. The data are presented as the mean ratio ± S.D. (error bars) of reduced to oxidized nucleotide levels from at least 2 separate experiments. D, survival of the indicated mutants 2 h after H₂O₂ challenge is shown. E, survival of WT and dksA-deficient Salmonella 2 h after challenge with 100 μm H₂O₂ is shown. Where indicated, PBS was supplemented with 0.4% glucose or 0.1% casamino acids. The data are the mean ± S.E. (error bars) from 4–12 independent observations from at least two independent experiments. *, p < 0.05; **, p < 0.01; ***, p < 0.001 compared with WT bacteria.