Metabolic efficiency due to regulation. The figure shows the adaptation of the E. coli TRN towards higher growth rate in response to change of medium. Growth rate obtained using constrained FBA is plotted for 4 trajectories of the TRN corresponding to aerobic minimal media with glutamine, lactate, fucose or acetate as the carbon source. The initial condition of the TRN in each case is the state the system would have been in for the glutamate aerobic medium. Dotted lines show the pure FBA growth rate in the 4 minimal media. The growth rate increases in three and remains constant in one of these trajectories.