Chemical Diversity and Biotechnological Applications of Pyoverdines

Many Pseudomonas species produce pyoverdines, fluorescent siderophores that comprise a conserved dihydroxyquinoline chromophore, a strain-specific peptide chain, and a small acyl side chain. Their exceptional affinity for Fe(III), and the more-recent discovery that they also bind some other metals, has prompted diverse biotechnological applications. These applications span iron biofertilisation and biocontrol, bioremediation and metal scavenging, infection imaging, Trojan horse antibiotic delivery, direct antibacterial activity, and tumour targeting. To support these and other applications, we establish a robust catalogue of structurally distinct pyoverdines, consolidating published lists with manual literature searches and resolving duplicate and conflicting structural assignments. We identify 83 pyoverdines with discrete peptide chains, ranging from 6 to 14 residues (median 8), together with five chromophore variants and six acyl side chains. Each peptide contains two oxidatively modified iron-binding residues, most often ornithine-derived hydroxamates, although 26.3% are threo-hydroxylated amino acids. Peptide composition is strongly biased towards small and polar residues, with just a few amino acid families accounting for an overwhelming majority of residues, and with L-stereochemistry slightly favoured (60.8%). We conclude that pyoverdines are tightly constrained in chelation chemistry yet highly plastic in recognition, and hope that our catalogue will provide a useful parts list for engineering tailored products.