Origin of metabolic intermediates in E. coli MG1655 single knockout strains Δ arcA and Δ iclR , and the double knockout strain Δ arcA Δ iclR cultivated in glucose abundant (batch) and glucose limiting (continuous) condtions. Standard deviations are calculated on different samples originating from different cultivations. The serine through EMP and the pyruvate through ED results were obtained from experiments using 50% 1-13C glucose and 50% naturally labeled glucose. To determine the remaining values a mixture of 20% U-13C glucose and 80% naturally labeled glucose was used. To determine the fractions resulting in the formation of OAA a Monte-Carlo approach was applied. For chemostat experiments, a dilution rate of 0.1 h-1 was set.