The central carbon metabolism network and the flux distributions of E. coli grown in normal and in paraquat-containing minimum media. The metabolic steps and their abbreviations are given in the List of abbreviations. The metabolites pyruvate, acetyl-coA and intracellular acetate have been treated as a unified pool, represented as one single node in the figure. Flux distributions under normal growth conditions (top) and following exposure to 70 μM paraquat (bottom) are without unit, normalized with respect to the rate of glucose uptake, which was the same in both the PQ-free and the PQ-treated conditions. Data in parentheses are variation ranges corresponding to 90% confidence intervals, which were computed from 2000 flux samples through the method described in ref .