PRODUCTION OF THE TRIACETECHOLATE SIDEROPHORE PROTOCHELIN BY AZOTOBACTER-VINELANDII

Azotobacter vinelandii grown in iron-limited medium containing 1 mu M molybdate released the catecholate siderophores azotochelin and aminoc helin [bis(2,3-dihydroxybenzoyl-lysine) and 2,3-dihydroxybenzoyl-putre scine, respectively] into the culture fluid, However these catecholate s were not observed when the medium contained 1 mM molybdate, but were replaced by another catecholate compound, The appearance of this new compound was not an artifact of extraction of the catecholates from th e culture fluid in the presence of high molybdate, Full and partial ac id hydrolysis and fast atom bombardment mass spectroscopy showed that the new compound was the tricatecholate protochelin, a product of the condensation of azotochelin and aminochelin, The production of protoch elin was iron-repressible and protochelin very rapidly decolorized the Chrome Azurol-S assay. Protochelin promoted the growth of the siderop hore-deficient A. vinelandii strain P100 under iron-restricted conditi ons and promoted Fe-55 uptake into iron-limited cells, confirming that protochelin can be used as a siderophore by A. vinelandii.