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

Abstract

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).

Mining elements of siderophore chirality encoded in microbial genomes

“…The ECD spectra were reproduced with permission from Ref. [22] (Copyright 2022 American Chemical Society) and from Ref. [23] with permission from the Royal Society of Chemistry.…”

“…We have now isolated and characterized the predicted siderophores with l Arg from the fish pathogen Yersinia ruckeri YRB [22], and l Lys from the human opportunistic pathogen Yersinia frederiksenii ATCC 33641 [23]. Y. ruckeri YRB produces the triscatechol siderophore ruckerbactin which is the linear l Ser oligoester, (DHB‐ l Arg‐ l Ser) 3 (Fig.…”

“…2C). The NRPS RucF in the BGC of Y. ruckeri YRB lacks an epimerization domain for L Arg; thus, ruckerbactin with L Arg is the diastereomer of trivanchrobactin produced by V. campbellii DS40M4 with D Arg [19,22]. Y. frederiksenii ATCC 33641 produces frederiksenibactin, the linear L Ser oligoester, (DHB-L Lys-L Ser) 3 (Fig.…”

“…(C) Structures of the related D-/L-Arg and D-/L-Lys siderophores. The ECD spectra of the Fe(III)-complexes shows the D CAA directs formation of the Λ Fe(III) conformer and the L CAA directs formation of a D Fe(III) complex.The ECD spectra were reproduced with permission from Ref [22]. (Copyright 2022 American Chemical Society) and from Ref [23].…”