FIG. 5.

Turkey serum as a source of Fe for 4169 and the transposon mutants Pho-6 and Pho-20. Growth conditions: 1, Chelex-treated CDM; 2, Chelex-treated CDM–36 μM FeSO₄; 3, Chelex-treated CDM–1.7% turkey serum; 4, Chelex-treated CDM–1.7% turkey serum–50 μM EDDA; 5, Chelex-treated CDM–1.7% turkey serum–50 μM EDDA–50 μM FeSO₄; 6, Chelex-treated CDM–1.7% turkey serum–50 μM EDDA–86 μM FeSO₄. Each bar represents the mean stationary-phase culture density obtained from three independent cultures. The error bars represent 1 standard deviation of the mean. An asterisk at the top of a bar indicates that the mean OD₆₀₀ of the mutant strain is significantly different from the mean OD₆₀₀ of 4169 for the particular growth condition (P ≤ 0.05). P values are noted for each asterisk.