Fig. S6.
Fe(III) citrate uptake and precipitation. (A) Iron accumulation in WT and ΔFtn cells incubated with 1 µM Fe(III). The uptake was performed as described in Fig 2B but with Fe(III)-citrate instead of Fe(III) EDTA. Between 0 and 30 min the ρFe of WT cells was, as expected, about sixfold higher in Fe(III) citrate (2.57 fmol/min per 106 cells) than in Fe(III) EDTA (0.42 fmol/min per 106 cells). For ΔFtn cells a fourfold difference was observed. More importantly, ρFe decreased after 30 min in WT and ΔFtn cells, indicating that the Fe(III) citrate source should be used only for short-term experiments. (B) Time course of iron precipitation from 1 µM Fe(III)citrate (1 Fe: 20 citrate) and 1 µM Fe(III)-EDTA (1:2) in cell-free Mf medium. After 20 min, 95% of Fe(III) citrate is still in solution.