Fig 3.

TtpC2 is essential for a functional TtpC2-TonB2 system in the uptake of radioactive [⁵⁵Fe]ferrioxamine. Ferrioxamine uptake assays were performed as described in Materials and Methods. The strains with the following genotypes were used: ΔtonB1 ΔttpC2 ΔttpC3 ΔvenB with pMMB208 (empty vector), pMMB208-ttpC2, and pMMB208-ttpC2 + KCN; ΔtonB1 ΔtonB2 ΔtonB3 ΔvenB with pMMB208 (empty vector), pMMB208-tonB2, and pMMB208-tonB2 + KCN. Samples were removed at the times indicated, and the amount of [⁵⁵Fe]ferrioxamine brought into the cells was determined by scintillation counting. This is a representative experiment that was done in triplicate.