FIG. 4.

Iron uptake activity in B. japonicum parent strain I110 (open squares) and fur strain GEM4 (closed squares). Cells were grown to mid-log phase in high-iron (A) or low-iron (B) medium, washed, and prepared as described in the text. At time zero, ⁵⁹Fe (0.1 μM final concentration) was added to the cells. Aliquots were removed at various times, collected, and counted as described in the text. Each point represents the average of three separate samples; standard deviation bars are shown. As controls, 1- and 8-min samples of cells that remained on ice throughout the time course were taken, and no uptake was observed (data not shown). The data shown are typical of two independent experiments.