Figure 1 .

Dependence of growth on glucose upon the presence of citrate for the ancestors and evolved strains. The ratio and error for growth parameters was calculated by fitting a log-linear model with the strain:media interaction terms and block as the dependent variables. Unlike the ancestors (first two values), strains from three of the evolved populations were strongly stimulated by citrate in terms of both (A) growth rate and (B) yield. The remaining nine Cit^- lineages, like their ancestors, exhibited little to no dependence upon citrate. We tested both ‘large’ (A-2A) and ‘small’ (A-2C) clones from the A-2 population, as it is known to have a stable, long-term polymorphism. Values represent the mean and 95% confidence intervals for the ratio of growth on glucose with citrate to growth without citrate for a given strain.