Fig 6. The cht locus is not required for efficient iron and heme utilization.

Growth curve of the wild type (closed symbol, solid line) and the (A) chtDE mutant (open symbol, dotted line) or (B) srt mutant (open symbol, dotted line) under normal conditions (light blue), iron-depleted conditions (green) and iron-replete conditions with 200 μM FeCl₃ (brown), 40 μM commercial Hb (predominantly metHb, purple) or HbO₂ at 25 μM (blue) or 50 μM (red) as the sole iron source. The arrow represents the time point at which the iron source was added. Bacterial growth was monitored by measuring the turbidity of the culture at 600 nm (OD₆₀₀). Growth of the wild type is shown with the solid lines and the mutant strains as the dotted lines. Error bars represent the standard error of the mean of n≥ 3 independent experiments.