Adaptive Evolution of the Lactose Utilization Network in Experimentally Evolved Populations of Escherichia coli
A) Inducer response histograms for reconstructed lacIΔTGGC and lacO1G11A mutants. The lacI mutation confers constitutive lac expression, whereas the lacO1 mutation confers a lower induction threshold and a graded response to inducer. B) Effect of the lacO1 mutation on the maximum lac expression level. Mean Plac-GFP expression levels during growth in saturating levels of inducer (100 µM TMG) are shown for the ancestor, evolved clone G+L3-1, lacO1G11A single mutant and the G+L3-1 clone with lacO1 reverted to the ancestral sequence (G+L3-1 lacO1anc). Standard error is shown, n = 4.