FIG. 7.

Metabolic flux distribution at the glycolysis-TCA cycle interface in chemostat cultures of pyruvate kinase-deficient E. coli PB25 calculated without any a priori assumptions on the activities of pyruvate kinase and the PTS system. This analysis was done with the experimental data used in Fig. 6 to elucidate whether our method identifies a reduced flux from PEP to pyruvate without explicitly including the pyruvate kinase knockout in the model. Flux values are relative to the specific glucose uptake rate and represent the mean of five to eight independent flux calculations that were initiated from random starting points. The maximum deviation of these independent calculations was 6, 6, and 2 to 8% of the specific glucose uptake rate for the top, middle, and bottom flux estimates given in the boxes, respectively. Fluxes marked by asterisks deviated by maximally 20%. The χ² values of the top, middle, and bottom flux estimates were 105, 46, and 450, respectively. The arrows indicate the direction of the estimated fluxes. Extracellular metabolites are denoted by the subscript ex. For abbreviations, see the legend to Fig. 2.