FeoB is not required for ferrous iron uptake in Campylobacter jejuni

Among strains of Campylobacter jejuni, levels of ferrous iron (Fe2+) uptake was comparable. However, C. jejuni showed a lower level of ferrous iron uptake than Escherichia coli. Consistent with studies of E. coli, Fe2+ uptake in C. jejuni was significantly enhanced by low Mg2+ concentration. The C. jejuni genome sequence contains a single known ferrous iron uptake gene, feoB, whose product shares 50% amino acid identity to Helicobacter pylori FeoB and 29% identity to E. coli FeoB. However, Fe2+ uptake could not be attributed to FeoB for several reasons. Site-directed mutations in feoB caused no defect in 55Fe2+ uptake. Among C. jejuni strains, various nucleotide alterations were found in feoB, indicating that some C. jejuni feoB genes are defective. In addition, uptake could not be attributed to the magnesium transporter CorA, since no reduction in 55Fe2+ uptake was observed in the presence of a CorA-specific inhibitor.