IRON UPTAKE FROM FERRIC CITRATE BY VIBRIO-ANGUILLARUM

We report here that Vibrio anguillarum possesses a non-inducible activ e transport system which can efficiently supply iron to the cell from ferric citrate, independently of the siderophore-based mechanisms. The strains tested were able to grow in CM9 medium in iron-restricted con ditions when ferric citrate was present in the medium. Moreover, the p resence of ferric citrate inhibited the production of siderophores in the strains tested. V. anguillarum cells and isolated membranes could incorporate Fe-55(3+) complexed by citrate, without a difference betwe en cells grown in the presence or absence of ferric citrate. The prese nce of 2,4-dinitrophenol, ferrozine, ferricyanide, trypsin, as well as low temperature produced a marked decrease or total inhibition of Fe- 55(3+) uptake by the cells. All these results suggest that iron uptake from ferric citrate in V. anguillarum must be an energy-dependent pro cess not induced by the presence of iron or citrate in the medium, med iated by a membrane protein(s), which may require an iron reduction st ep to function.