FIG. 5.

To determine the effect of soluble iron on metabolic activity, C. burnetii was labeled with [³⁵S]methionine for 2 h in a citrate buffer (pH 4.5) containing 0, 0.1, or 0.2 mM iron. Proteins expressed during this in vitro incubation were visualized by autoradiography to compare expression. Equal numbers of cells were loaded onto all lanes. Total expression is reduced by 38% in an average of five experiments at 0 mM iron, while expression of a 20-kDa and a 17-kDa protein (indicated by arrows) is reduced at 0.2 mM iron.