FIG. 3.

Expression of a bhuA-lacZ fusion in B. abortus 2308 during growth in low-iron minimal medium (filled bars) and low-iron minimal medium supplemented with 50 μM FeCl₃ (open bars). β-Galactosidase activity is expressed on the y axis in Miller units (27). The data are means and standard deviations for triplicate determinations from a single culture for each strain at each experimental time point in a single experiment. The data are representative of multiple (≥3) experiments from which equivalent results and statistical trends were obtained. The β-galactosidase levels produced by the base pMR15 plasmid in B. abortus 2308 during growth in low-iron minimal medium or in this medium supplemented with 50 μM FeCl₃ never exceeded 200 Miller units in the assays (data not shown).