Bioinorganic Control of Coral Pathogens: Pyoverdine-Mediated Iron Depletion Against Vibrio spp.

Corals are marine invertebrates that form reefs and harbor nearly 25% of marine biodiversity. Climate change increases sea surface temperatures, causing bleaching and favoring infections by Vibrio spp., both contributing to coral mortality. Here, we propose a bioinorganic strategy to inhibit pathogenic Vibrio through iron depletion using the siderophore pyoverdine. Pyoverdine was extracted from Pseudomonas aeruginosa cultures, purified, and characterized by spectroscopic and mass spectrometric techniques. The ferric-pyoverdine complex showed 1:1 stoichiometry and high stability (logK ≈ 10³²). Biological assays demonstrated strong inhibition of Vibrio shilonii and Vibrio coralliilyticus, with MIC values of 50 and 100 µmol L⁻¹, respectively, and growth reduction even at the lowest concentration tested. Pyoverdine also impaired motility and biofilm formation at sub-lethal doses. These results highlight bacterial iron acquisition as a promising target to mitigate coral diseases and improve reef resilience under climate change.