Figure 4 .

Direct addition of iron, but not spent medium, stimulates growth on glucose for citrate-dependent evolved lineages. 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. Both the relative (A) growth rate and (B) yield of the three strains from populations stimulated by sodium citrate (black circles) were at least partially enhanced by direct addition of 10 μM Fe (II) (as ammonium iron sulfate, red squares). In contrast, growth in spent media re-supplemented with glucose (blue triangles) did not stimulate growth. Values represent the mean and 95% confidence intervals for the ratio of growth of that strain on glucose with the supplement to growth without.