The structure of two pyoverdins lnxxha?.ed in iron-deficient cultures c~ Pseudomonas fluorescens CHAO, a bacterium responsible for suppression of fim~ diseoses in plant roots, was elucidated using essentially FAB-MS and homonuclenr and heteronuclear 2D NMR techniques. It is a partly cyclic chromopeptide: chromophore-Asp-OHOrn-Lys-cyclo-(Thr-Ala-Ala-OHOm-Lys) forming a sixteen-membered lactone ring.