Experimental evidence indicating that microbes tune their enzyme levels to maximise growth rate.

In each example, the wild type (WT) is shown to express enzyme concentrations at which the growth rate μ is approximately maximal. Axes show enzyme concentrations relative to wild type (WT) levels (abscissa) and growth rates relative to WT. Data adapted from: A, [9]; B, [4, 5, 6], C, [3]; D, [2]. Abbreviations: GAL1, galactokinase; GAL2, Galactose permease; GAL7, Galactose-1-phosphate uridyl transferase; LDH, lactate dehydrogenase; PFK, phosphofructokinase; LAS, las operon; GAPDH, glyceraldehyde 3-phosphate dehydrogenase; Glc, glucose; Succ, succinate. In [9] there are many other examples, including several proteins that do not show levels at which growth rate is optimised.