3927529

Identification of lignin-derived organic iron (Fe) ligands by Fe isotopologue analysis coupled with metabolomics

Date
August 15, 2023
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Plant biomass-derived organic iron (Fe) ligands can be important components of stable organic carbon in soils due to their strong capability to bind with Fe minerals, however, most of them are still molecularly uncharacterized. To fill in this critical knowledge gap, high-performance liquid chromatography (HPLC)-high-resolution Orbitrap mass spectrometry (HRMS), Fe isotopologue screening, and metabolomic analysis were coupled together to identify organic ligands generated during the microbial degradation of lignin. For the metabolomic analysis, a series of tools were used including but not limited to MZmine, SIRIUS, and GNPS dashboard. Certain criteria were developed and used for the identification of organic Fe ligands: 1) MZmine captured features; 2) Fe isotopologue matching (54Fe vs 56Fe) for Fe(III)-added media; 3) Detection of apo-ligands feature considering the complexes of [Fe(III)ClxLy]- (x = 1–3; y = 1–2) (in -ve mode); 4) Additional (Cl) isotopologue matching; 5) GNPS repository matching or MS library matching; 6) validation with authentic standards. Among the compounds generated from the 30-day microbial degradation of kraft lignin by Pseudomonas putida KT2440, >6000 HPLC-HRMS features were captured by MZmine analysis. Fe isotopologue screening identified 47 candidate ligands with complexes formed upon the addition of FeCl3, and 23 candidate ligands with Cl isotopologue matching was further screened out. Among the ligands with Fe and Cl isotopologue matching and detection of apo-ligands, four ligands were matched with the MS library, including hesperetin and isotaxiresinol. Furthermore, SIRIUS was used to predict the structure of the captured ligands. Network analysis has indicated interesting transformation as well as possible generation reactions for the candidate ligands. This study has developed a protocol to identify organic ligands in complex environmental media and identified interesting ligands generated from microbial degradation of lignin, which can be potential compounds to bind with Fe minerals and be stabilized in soil environment. Such molecular-level understanding of plant macromolecule-derived organic ligands can advance our understanding and prediction for the biogeochemical cycling of organic carbon in soil environments.

Speakers

Speaker Image for Srinidhi Lokesh
Srinidhi Lokesh, Research Assistant
Speaker Image for Rene Boiteau
Assistant Professor, Oregon State University

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