while Acidovorax sp. strain JS42 expressing wt 2NTDO could not grow on 3-and 4-nitrotoluene, prolonged exposure resulted in mutations in the codons for residues M248, L238, and I204 that supported growth of 4NT + and 3NT + strains on the respective substrate (Table ). In Figure , these observations are shown as changes of O 2 uncoupling, ∆f O 2 -uc , and of inverse doubling times, ∆(1/doubling time), where no growth is assigned a value of 0 h -1 . Increased growth rates of 3-NT + and 4-NT + strains with their target substrate 3-and 4-nitrotoluene are correlated linearly with their efficiency gain (top left quadrant in Figure ). Conversely, the loss of efficiency is accompanied by decreased growth rates on non-target substrates (bottom right quadrant of Figure ). The most notable exceptions of these trends stem from 3NT