FIG. 4.

Ferric and ferrous iron uptake by C. jejuni NCTC11168 is iron and riboflavin responsive and is increased in the fur mutant. Rates of ⁵⁵Fe²⁺ (A) and ⁵⁵Fe³⁺ (B) uptake in the wild-type, ribB mutant, and fur mutant strains. Cultures were grown in iron-limited (1 μM FeCl₃; indicated as −iron) and iron-replete (40 μM FeCl₃, indicated as +iron) MEMα or in standard (20 μM FeCl₃) MEMα without and with additional supplementation with 50 μM riboflavin (indicated as −riboflavin and +riboflavin). Data shown are from two independent experiments performed in triplicate. The ribB mutant could not be tested in MEMα without added riboflavin because of the riboflavin auxotrophy; the absence of data for this sample is indicated by an asterisk.