Ruckerbactin Produced by Yersinia ruckeri YRB Is a Diastereomer of the Siderophore Trivanchrobactin Produced by Vibrio campbellii DS40M4.

The Gram-negative bacterium Yersinia ruckeri is the causative agent for enteric red mouth disease in salmonids. The genome of Y. ruckeri YRB contains a biosynthetic gene cluster encoding the biosynthesis of catechol siderophores that are diastereomeric with the known vanchrobactin class of siderophores, (DHB D Arg L Ser) (1-3) . Ruckerbactin ( 1 ), produced by Y. ruckeri YRB, was found to be the linear tris-l-serine ester composed of l-arginine and 2,3-dihydroxybenzoic acid, (DHB L Arg L Ser) 3 . The biscatechol, (DHB L Arg L Ser) 2 ( 2 ), and monocatechol, DHB L Arg L Ser ( 3 ), compounds were also isolated and characterized. The macrolactone of ruckerbactin was not detected. The presence of L Arg in ruckerbactin makes it the diastereomer of trivanchrobactin with D Arg. The electronic circular dichroism spectra of Fe(III)-ruckerbactin and Fe(III)-trivanchrobactin reveal the opposite enantiomeric configurations at the Fe(III) sites. Fe(III)-ruckerbactin adopts the Δ configuration, and Fe(III)-trivanchrobactin adopts the Λ configuration. Y. ruckeri YRB was also found to produce the antimicrobial agent holomycin ( 4 ).