Rhizobactin B is the preferred siderophore by a novel Pseudomonas isolate to obtain iron from dissolved organic matter in peatlands

• Published in: Biometals Vol. 33; no. 6; pp. 415 - 433
• Main Authors: Kügler, Stefan, Cooper, Rebecca E., Boessneck, Johanna, Küsel, Kirsten, Wichard, Thomas
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.12.2020; Springer Nature B.V
• Subjects: Aluminum; Bacteria; Biochemistry; Biogeochemical cycles; Biogeochemistry; Biological activity; Biomedical and Life Sciences; Cell Biology; Chelation; Coordination compounds; Copper; Dissolved organic matter; Heavy metals; Iron; Iron - chemistry; Iron - isolation & purification; Life Sciences; Magnetic Resonance Spectroscopy; Mass spectrometry; Mass spectroscopy; Medicine/Public Health; Microbiology; Molecular Structure; NMR; NMR spectroscopy; Nuclear magnetic resonance; Peat; Peatlands; Pharmacology/Toxicology; Plant Physiology; Polycarboxylic acids; Pseudomonas; Pseudomonas - chemistry; Pyoverdines; Siderophores; Siderophores - chemistry; Siderophores - isolation & purification; Tandem Mass Spectrometry; Zinc; Iron; Dissolved organic matter; Metallophore; Siderophore; Peatland; Pseudomonas
• ISSN: 0966-0844; 1572-8773
• DOI: 10.1007/s10534-020-00258-w

Bacteria often release diverse iron-chelating compounds called siderophores to scavenge iron from the environment for many essential biological processes. In peatlands, where the biogeochemical cycle of iron and dissolved organic matter (DOM) are coupled, bacterial iron acquisition can be challenging even at high total iron concentrations. We found that the bacterium Pseudomonas sp. FEN, isolated from an Fe-rich peatland in the Northern Bavarian Fichtelgebirge (Germany), released an unprecedented siderophore for its genus. High-resolution mass spectrometry (HR-MS) using metal isotope-coded profiling (MICP), MS/MS experiments, and nuclear magnetic resonance spectroscopy (NMR) identified the amino polycarboxylic acid rhizobactin and a novel derivative at even higher amounts, which was named rhizobactin B. Interestingly, pyoverdine-like siderophores, typical for this genus, were not detected. With peat water extract (PWE), studies revealed that rhizobactin B could acquire Fe complexed by DOM, potentially through a TonB-dependent transporter, implying a higher Fe binding constant of rhizobactin B than DOM. The further uptake of Fe-rhizobactin B by Pseudomonas sp. FEN suggested its role as a siderophore. Rhizobactin B can complex several other metals, including Al, Cu, Mo, and Zn. The study demonstrates that the utilization of rhizobactin B can increase the Fe availability for Pseudomonas sp. FEN through ligand exchange with Fe-DOM, which has implications for the biogeochemical cycling of Fe in this peatland.