Improved Characterization of Soil Organic Matter by Integrating FT-ICR MS, Liquid Chromatography Tandem Mass Spectrometry, and Molecular Networking: A Case Study of Root Litter Decay under Drought Conditions.
Nicole DiDonatoAlbert Rivas-UbachWilliam R KewNoah W SokolChaevien S ClendinenJennifer E KyleCarmen Enid MartínezMegan M FoleyNikola TolićJennifer Pett-RidgeLjiljana Paša-TolićPublished in: Analytical chemistry (2024)
Understanding of how soil organic matter (SOM) chemistry is altered in a changing climate has advanced considerably; however, most SOM components remain unidentified, impeding the ability to characterize a major fraction of organic matter and predict what types of molecules, and from which sources, will persist in soil. We present a novel approach to better characterize SOM extracts by integrating information from three types of analyses, and we deploy this method to characterize decaying root-detritus soil microcosms subjected to either drought or normal conditions. To observe broad differences in composition, we employed direct infusion Fourier-transform ion cyclotron resonance mass spectrometry (DI-FT-ICR MS). We complemented this with liquid chromatography tandem mass spectrometry (LC-MS/MS) to identify components by library matching. Since libraries contain only a small fraction of SOM components, we also used fragment spectral cosine similarity scores to relate unknowns and library matches through molecular networks. This integrated approach allowed us to corroborate DI-FT-ICR MS molecular formulas using library matches, which included fungal metabolites and related polyphenolic compounds. We also inferred structures of unknowns from molecular networks and improved LC-MS/MS annotation rates from ∼5 to 35% by considering DI-FT-ICR MS molecular formula assignments. Under drought conditions, we found greater relative amounts of lignin-like vs condensed aromatic polyphenol formulas and lower average nominal oxidation state of carbon, suggesting reduced decomposition of SOM and/or microbes under stress. Our integrated approach provides a framework for enhanced annotation of SOM components that is more comprehensive than performing individual data analyses in parallel.
Keyphrases
- organic matter
- liquid chromatography tandem mass spectrometry
- mass spectrometry
- ms ms
- multiple sclerosis
- climate change
- plant growth
- liquid chromatography
- solid phase extraction
- heat stress
- healthcare
- low dose
- big data
- escherichia coli
- biofilm formation
- magnetic resonance
- electronic health record
- capillary electrophoresis
- cystic fibrosis
- staphylococcus aureus
- optical coherence tomography
- nitric oxide
- machine learning
- amino acid
- human milk