| Sumario: | Vibrio ordaliiis the causative agent of vibriosis, mainly in salmonid fishes, and its virulencemechanisms are still not completely understood. In previous works we demonstrated thatV. ordaliipossess several iron uptake mechanisms based on heme utilization and siderophore production.The aim of the present work was to confirm the production and utilization of piscibactin as asiderophore byV. ordalii. Using genetic analysis, identification by peptide mass fingerprinting (PMF)of iron-regulated membrane proteins and chemical identification by LC-HRMS, we were able toclearly demonstrate thatV. ordaliiproduces piscibactin under iron limitation. The synthesis andtransport of this siderophore is encoded by a chromosomal gene cluster homologous to another onedescribed inV. anguillarum, which also encodes the synthesis of piscibactin. Usingβ-galactosidaseassays we were able to show that two potential promoters regulated by iron control the transcriptionof this gene cluster inV. ordalii. Moreover, biosynthetic and transport proteins corresponding topiscibactin synthesis and uptake could be identified in membrane fractions ofV. ordaliicells grownunder iron limitation. The synthesis of piscibactin was previously reported in other fish pathogenslikePhotobacterium damselaesubsp.piscicidaandV. anguillarum, which highlights the importance ofthis siderophore as a key virulence factor in Vibrionaceae bacteria infecting poikilothermic animals
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