Siderophores produced by Vibrio anguillarum in vitro and in infected rainbow trout, Oncorhynchus mykiss (Walbaum)

. Ten strains of Vibrio anguillarum produced three different types of iron-binding compounds when cultured under different conditions. These were (1) a common phenolate siderophore produced by all strains. (2) a hydroxamate siderophore produced by three strains and (3) a second phenolate siderophore, tentatively identified as anguibactin, produced by V. anguillarum strain 775 and two other strains, all of which contained a plasmid of 45–50 Md. The relative affinities of these siderophores, determined by competition for 55Fe was: anguibactin < hydroxamate siderophore < common phenolate siderophore. However, under these conditions, none removed iron from purified aerobactin. Experimental infection of rainbow trout. Oncorhynchus mykiss (Walbaum), showed that only the common phenolate siderophore was detected in the kidney and spleen of fish infected with strains 91079 and NCIMB6. The hydroxamate siderophore produced in vitro by strain NCIMB6 was not detected in vivo. However, in the kidney of fish infected with strain 775, both the common phenolate siderophore and anguibactin were detected, showing that a second uptake system is required by strain 775 in vivo and that the iron-uptake system based on the common phenolate siderophore is defective.