pyoverdine

Pyoverdine is a yellow-green fluorescent siderophore produced by various Pseudomonas species, most notably Pseudomonas aeruginosa. It functions to scavenger ferric iron (Fe3+) from the environment under iron-limiting conditions, forming ferripyoverdine that is then taken up by the bacterial cell.

Its chemical structure comprises a dihydroxyquinoline chromophore linked to a highly variable peptide moiety; the peptide sequence defines different pyoverdine variants (the types are often referred to by their corresponding PVD type). The fluorescence is a characteristic feature of both the ferrated and non-ferrated forms.

Biosynthesis is encoded by the pvd gene cluster and proceeds via nonribosomal peptide synthetases and associated tailoring enzymes such as PvdL, PvdI, PvdJ, and PvdD that assemble the chromophore-linked peptide moiety; the molecule is exported to the extracellular milieu where it captures Fe3+.

Ferripyoverdine is recognized by outer membrane receptors FpvA (and related receptors such as FpvB) in P. aeruginosa; uptake is energized by the TonB-ExbB-ExbD complex, and Fe3+ is released in the cytoplasm for use in metabolic processes.

Iron limitation relieves Fur repression and enables the activity of PvdS, an extracytoplasmic function sigma factor that drives expression of the pvd gene cluster and, in P. aeruginosa, several virulence factors, including exotoxin A and certain proteases.

In the host, pyoverdine-mediated iron acquisition supports bacterial growth in iron-poor environments such as the cystic fibrosis lung and burn wounds; the system also intersects with host defenses, as siderophore sequestration by host proteins can limit uptake.

Because iron acquisition via pyoverdine is essential for virulence in many contexts, the pyoverdine system is a target for anti-virulence strategies, including inhibitors of biosynthesis or transporter function and siderophore–antibiotic conjugates that exploit ferripyoverdine uptake.