UPTAKE OF IRON FROM FERRIC CITRATE IN THE CYANOBACTERIA SYNECHOCYSTIS PCC6803

Iron is an essential element for bacterial growth. Its intracellular concentration is mainly controlled at the uptake level which is mediated by iron-dicitrate transport in various prokaryotes. We report here that 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. These data suggest the existence of a specific ferric citrate receptor on the cyanobacterial membrane.