Effect of iron and growth inhibitors on siderophores production by Pseudomonas fluorescens

The ability of Pseudomonas to grow and to produce siderophores is dependent on the iron content and the type of carbon sources in the medium. Under conditions of low-iron concentration the Pseudomonas isolates studied produced yellow-green fluorescent iron-binding peptide siderophores and the biosynthesis of this siderophores was affected by several different environmental parameters. Four basal media, supplemented with different concentration of iron, were employed to study the effect of iron and different organic carbon sources on siderophore production in Pseudomonas fluorescens. The highest siderophores concentration was obtained in succinate medium. Ferric iron increased the growth yield and completely repressed siderophores production above 200 μg/l, but had a positive effect below 160μg/l. Penicillin and lead elicited the production of siderophores in the presence of excess iron. Pre-treatment of the standard succinate medium witha,a-dipyridyl and 8-hydroxyquinoline to reduce the concentration of iron diminished both the growth yield and siderophore production, but a,a-dipyridyl increased significantly the amount of siderophores produced in the presence of 0.20 mg/l of the chelating ion . Key words: Pseudomonas fluorescens, siderophores, iron, penicillin, lead, a,a-dipyridyl , 8-hydroxyquinoline.