The persistence of soil organic carbon in the mineralosphere as a function of the soil microbiome, proteome, and exometabolome
EMSL Project ID
49791
Abstract
Soils store more carbon (C) than the atmosphere and biosphere combined, yet the fundamental mechanisms that regulate the persistence of this vast pool of C remain elusive. Soil organic matter (SOM) is considered stable if it is protected from microbial decomposition. Association with soil minerals provides substantial protection of SOM, with some mineral-associated SOM persisting for thousands of years. However, we know that not all mineral-associated carbon is protected from microbial degradation for long time periods. Here, we investigate the persistence of SOM, using stable isotopes (13C) to track the fate of C associated with soil minerals, with a focus on the influence of mineralogy, plant growth, and the microbial community. Our metagenomic analyses of rhizopshere and the minearlosphere microbiomes provide a critical framework for analyzing and interpreting the soil (meta) proteome and exometabolome as a basis for understand the microbial and molecular controls on SOM turnover and persistence. Our experiments are enabled by stable isotope tracing (13C) techniques, allowing us to follow carbon from a growing plant root onto mineral surfaces (sorption), and back off mineral surfaces into the soil solution and microbial bodies (desorption). We conduct sorption experiments by incubating pure minerals (ferrihydrite, quartz, kaolinite) and density-fractionated minerals in two soils (California grassland and Oklahoma marginal agricultural soil) with two plant types (Avena barbata -- slender oat grass, and Panicum virgatum -- switchgrass) to track association of 13C plant-derived SOM onto mineral surfaces. We conduct desorption experiments by incubating minerals (ferrihydrite, quartz, kaolinite and density-fractionated minerals) coated with 13C-labeled SOM in the same soil-plant systems and tracing the transformation and loss of mineral associated SOM into the soil solution and into microbial bodies. Leveraging the capabilities at EMSL will allow us to: (1) target metabolic pathways controlling SOM turnover by linking (meta)proteomics and protein stable isotope probing (Pro-SIP) with our metagenomes and SIP metagenome from the same soil, and (2) characterize SOM associated with mineral surfaces and desorbed from the minerals surface into the soil solution with a combination of nuclear magnetic resonance spectrometry (13C-NMR), Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS), and laser ablation electrospray ionization mass spectrometry (LAESI-MS/MS) metabolomics. By linking microbial utilization of mineral-associated SOM with changes in the chemistry of mineral-SOM associations during sorption and desorption, we can begin to build a mechanistic framework for the processes controlling the persistence of C in soil.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2017-10-01
End Date
2019-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Team Members