Iron uptake with ferripyochelin and ferric citrate by Pseudomonas aeruginosa

Abstract

Pyochelin is a Fe-binding compound produced by P. aeruginosa and demonstrates siderophore activity by its involvement in Fe transport. During the transport process, an energy-independent association of [55Fe]ferripyochelin with bacteria occurred within the initial 30 s of reaction, followed by an energy-dependent accumulation of Fe. The energy-independent association with iron appeared to be at the surface of the bacteria because the Fe could be washed from the cells with thioglycolate, whereas accumulated Fe was not washed from the bacteria. Energy-independent association of Fe with bacteria and energy-dependent accumulation of iron in the presence of ferripyochelin varied concomitantly in cells grown under various conditions, but pyochelin synthesis appeared to be controlled separately. 55Fe complexed with citrate was also taken up by P. aeruginosa with a lower level of initial cell association. Bacterial mechanisms for Fe uptake from ferric citrate were present in cells grown in a variety of media and were in lowest levels in cells grown in citrate. The synthesis of bacterial components for Fe uptake from ferric citrate and from ferripyochelin was inhibited by high concentrations of Fe supplied in growth media.