FIG. 4.

BacA deficiency does not have an effect on iron accumulation. ⁵⁵FeCl₃ uptake experiments were performed with the bacA::hyg mutant or the parental strain H37Rv. After 4 days of growth in iron-deficient medium, cultures were adjusted to the same bacterial concentration and ⁵⁵FeCl₃ was added to a final concentration of 0.5 μCi ml⁻¹. At the indicated times, the bacterial concentration was assessed by OD₆₅₀ measurements and samples were collected. The iron uptake was quantified by measurements of the radioactivity accumulated in the bacterial pellets. The results are expressed as the ratio of the radioactivity measured divided by the OD₆₅₀ value obtained at the corresponding time. Two different iron conditions were tested, i.e., iron-depleted medium and iron-deficient medium (see Materials and Methods for details).