FIG 2.

Effect of norvaline on the production of ppGpp. Wild-type (WT) R. eutropha alone (B and C) or both the WT and the ΔspoT2 mutant (A, D, and E) were grown on MSM-fructose medium (A and B) or on NB-gluconate medium (C to E) with (arrows) or without (w/o) norvaline. Norvaline (0.1%, wt/vol) was added when the OD₆₀₀ had reached 0.7 (≈20 h after inoculation) (A) or at 0 h (D) or 12 h (E). ppGpp concentrations were determined in samples taken at the times indicated. Inoculations were carried out with NB-grown (stationary) seed cultures. All experiments were performed as biological triplicates. Bars represent mean values; error bars, standard deviations. Statistical significance was determined using the Holm-Sidak method (*, P < 0.05; **, P < 0.01).