Siderophore-mediated iron transport in Bacillus subtilis and Corynebacterium glutamicum

Abstract

Hexadentate bacillibactin is the siderophore of Bacillus subtilis and is structurally similar to the better known enterobactin of Gram-negative bacteria such as Escherichia coli. Although both are triscatecholamide trilactones, the structural differences of these two siderophores result in opposite metal chiralities, different affinity for ferric ion, and dissimilar iron transport behaviors. Bacillibactin was first reported as isolated from Corynebacterium glutamicum and called corynebactin. However, failure of iron-starved C. glutamicum to transport 55Fe bacillibactin and lack of required bacillibactin biosynthetic genes suggest that bacillibactin is not the siderophore produced by this organism. Iron transport mediated by siderophores in B. subtilis occurs through a transport process that is specific for the iron chelating moiety, with parallel pathways for catecholates and hydroxamates. For bacillibactin, enterobactin, and their analogs, neither chirality nor presence of an amino acid spacer affects the uptake and transport process, but alteration of the net charge and size of the molecule impedes the recognition.

Characterization of a Bacillus subtilis transporter for petrobactin, an anthrax stealth siderophore

“…B. subtilis disruption mutant strains yclNd (yclN::pMUTIN2), yclPd (yclP::pMUTIN2), and yclQd (yclQ::pMUTIN2) in the strain 168 background were obtained from E. Dervyn (Institut National de la Recherche Agronomique, Paris) (22). Ironlimited medium was prepared as described previously (5). Siderophores were obtained as described previously (20).…”

“…Transport assays in B. subtilis 168, yclNd, yclPd, yclQd, and the complemented mutant strains were performed as described previously (5,20). Data were normalized to 1 mL of bacterial cultures.…”

“…Bacillus subtilis is the prototypical Gram-positive bacterium, and recent studies of its iron metabolism have elucidated multiple aspects of siderophore synthesis, transport, and regulation (4)(5)(6)(7)(8). B. subtilis produces bacillibactin (BB), a 2,3-dihydroxybenzoyl-GlyThr trilactone siderophore ( Fig.…”

Structure and Mechanism of the Siderophore-Interacting Protein from the Fuscachelin Gene Cluster of Thermobifida fusca

“…For Gram-positive bacteria, these include EntS-type major facilitator superfamily (MFS) exporter and import through a FepCDG-like multifunctional ABC transporter system associated with a FepB-like transporter through the ligand exchange mechanism. 33,34,35 Imported ferric iron bound to siderophore must be released to be made available to cellular machinery. One strategy for iron release is through hydrolytic destruction of the siderophore by esterases of the α,β-hydrolase family of enzymes, represented by the E. coli fes, iroD and iroE gene products and is a common strategy for macrolactone-based siderophores.…”

Bacillus cereus iron uptake protein fishes out an unstable ferric citrate trimer

“…55 Fe-citrate uptake assays were performed as described previously (24,33,34). A detailed protocol is described in SI Materials and Methods.…”