UPTAKE OF IRON FROM FERRIC CITRATE IN THE CYANOBACTERIA SYNECHOCYSTISPCC6803

Iron is an essential element for bacterial growth. Its intracellular c oncentration is mainly controlled at the uptake level which is mediate d by iron-dicitrate transport in various prokaryotes. We report here t hat the cyanobacterium Syncchocystis PCC6803 takes up iron from ferric citrate. This process is dependent of the iron : citrate ratio, with a better efficiency for the highest concentration of citrate. The iron -citrate complex is the substrate of this active uptake, inhibited in part hy the uncoupler FCCP. Iron starvation activates this uptake. The se data suggest the existence of a specific ferric citrate receptor on the cyanobacterial membrane.