Fig. 5.

Steady-state pool concentration obtained by the filtration and wash strategy. Cells were grown in NH₄⁺-glycerol, NH₄⁺-glucose, or proline-glycerol medium. Samples were collected at 3 to 5 different cell densities for each culture during its exponential phase of growth. Wash medium was identical to the starting medium with 20 mM either NH₄⁺ or proline. The results were from two sets of independent experiments. Average doubling times were 63 min for the wild type (WT), 68 min for the GDH⁻ mutant, 65 min for the GOGAT⁻ mutant, 48 min for the wild type grown in NH₄⁺-glucose, and 99 min for the wild type grown in proline-glycerol.