The nitrogen-fixing Gram-negative bacterium Rhizobium meliloti DM4 when cultured on a low-iron media forms a siderophore which corrects iron starvation in the microorganism. The compound N2-[2- [ (1-carboxyethyl)amino]ethyl]- N6-( 3-carboxy-3-hydroxy- 1 -oxopropyl)lysine, designated rhizobactin, contains ethylenediaminedicarboxyl and a-hydroxycarboxyl moieties as metal-coordinating groups. The ethylenediamine group is novel as a natural product and is unprecedented as a ligand in the siderophore series, which characteristically contain catechol or hydroxamate functional groups.