THE ANGR PROTEIN AND THE SIDEROPHORE ANGUIBACTIN POSITIVELY REGULATE THE EXPRESSION OF IRON-TRANSPORT GENES IN VIBRIO-ANGUILLARUM

Vibrio anguillarum virulence is associated with the presence of a plas mid-mediated iron-uptake system expressed under iron-limiting conditio ns, which consists of the siderophore anguibactin and specific iron-tr ansport proteins. This system is maximally expressed under iron-limiti ng conditions and requires the AngR protein that acts as a positive re gulator of anguibactin biosynthesis and also possess an EntE-like enzy matic function that may play a role in anguibactin biosynthesis. In th is work, we demonstrate that in addition to possessing these functions related to anguibactin production, AngR also positively regulated tra nscription of the iron-transport genes fatA and fatB. We also show tha t transcription of angR is repressed by Fur under iron-rich conditions . In addition, we present evidence that anguibactin itself enhanced tr anscription of the iron-transport genes fatA and fatB, independently o f AngR and the trans-acting factor (TAF) product(s). The presence of e ither AngR (together with the TAF product(s)) or anguibactin alone led to a partial level of expression of the iron-transport genes fatA and fatB, while full expression is achieved when AngR, the TAF products a nd anguibactin are all present.