Fig 2.

Effect of citrate on luminescence. Shown is luminescence as a function of cell density (A) or peak luminescence per OD₅₉₅ (B) for wild-type (WT) ES114 cultures grown in aerobic shake flasks in SWTO medium supplemented with 43 μM FeSO₄ without further additions or supplemented with 20 mM citrate or with 20 mM citrate and 2 mM additional FeSO₄. In panel B, lowercase letters shared between bars indicate no statistically significant difference (P > 0.9), whereas different letters indicate a significant difference (P < 0.001), based on a one-way analysis of variance and Tukey's honestly significant difference test. Data are representative of at least three independent experiments. Error bars (some too small to visualize) indicate standard deviations (n = 3) for the one experiment shown in each panel.