Figure 5

NAD(P)+/NAD(P)H and NAD+/NADH ratios in the wildtype and tadD mutant. A. NAD(P)⁺/NAD(P)H ratios decrease during early nitrogen limitation. Wildtype R. opacus PD630 and the tadD mutant were grown in minimal medium supplemented with either 1% (w/v) or 0.15% (w/v) ammonium sulfate, the resulting cell lysates were assayed for NAD(P)⁺ and NAD(P)H concentrations. Consistent with our data concerning ND-G3PDH activity we observed a decrease in the ratio of NAD(P)⁺/NAD(P)H under nitrogen limitation as compared to nitrogen replete conditions. Additionally, we see no change in the ratio of NAD(P)⁺/NAD(P)H in the tadD mutant. B. The ratio of NAD⁺/NADH increases under nitrogen limiting conditions. Cell lysates from above were also assayed for NAD⁺ and NADH concentrations. We observed a marked increase in the ratio or NAD⁺ to NADH under nitrogen limiting conditions as compared to nitrogen replete conditions, while no difference was observed in the tadD mutant. It is worth noting that the NAD⁺/NADH ratio in the tadD mutant is significantly lower than that observed for the wildtype.