Structure of synechobactins, new siderophores of the marine cyanobacterium Synechococcus sp PCC 7002

The coastal marine cyanobacterium Synechococcus sp. PCC 7002 produces three amphiphilic siderophores, synechobactins A-C, under iron-limiting growth conditions. The synechobactins are comprised of a citric acid backbone linked to two 1, 3-diaminopropane units. The terminal amine of one diaminopropane is acetylated and hydroxylated forming one hydroxamate group. The terminal amine of the other diaminopropane is appended to one of a series of fatty acids and N-hydroxylated on the fatty acid amide forming the second hydroxamate linkage. Synechobactins A-C differ among themselves in the identity of the fatty acid residue as dodecanoic acid, decanoic acid, or octanoic acid, respectively. They are the first structurally elucidated siderophores from marine cyanobacteria and are related to schizokinen, a previously identified siderophore that lacks amphiphilic character, isolated from other bacteria including freshwater cyanobacteria.