Jocelyn Richardson

All Publications

• Phosphorus availability influences potassium chemistries in the ectomycorrhizal fungi Pisolithus tinctorius and Paxillus ammoniavirescens. Fungal biology Richardson, J. A., Higuita-Aguirre, M. I., Rose, B. D., Garcia, K. 2026; 130 (4): 101776

  Abstract

  Ectomycorrhizal (ECM) fungi play essential roles in tree nutrition and soil biogeochemical cycling by mediating the acquisition and storage of mineral nutrients. While phosphorus and nitrogen exchange between host plants and ECM fungi are well documented, potassium (K) dynamics remain poorly understood. Using synchrotron-based X-ray fluorescence (XRF) imaging and K-edge X-ray absorption near-edge structure (XANES) spectroscopy, we compared the spatial distribution and chemical speciation of K and P in two Boletales fungi - Pisolithus tinctorius and Paxillus ammoniavirescens - grown under P-sufficient and P-limited conditions. Both species exhibited reduced K and P abundance under low P, but P. ammoniavirescens maintained higher and more spatially variable concentrations of both elements. K XANES analyses revealed distinct species-specific chemical fingerprints: P. tinctorius displayed a reduced diversity of K species under P limitation, dominated by humic- and tartrate-bound forms, whereas P. ammoniavirescens preserved a broader suite of organic and inorganic K compounds, including persistent KH2PO4. These results indicate that ECM fungi employ divergent strategies for K and P management, reflecting their ecological specialization. P. tinctorius adopts a conservative nutrient-retention strategy, while P. ammoniavirescens exhibits greater physiological plasticity. Together, these findings provide new insight into the functional and evolutionary diversity of nutrient regulation among ECM symbionts.

  View details for DOI 10.1016/j.funbio.2026.101776

  View details for PubMedID 42191244

• Effects of Polymer Morphology on Solvent and Catalyst Accessibility during Polyethylene and Polystyrene Autoxidation. JACS Au Maurya, A. K., Asundi, A. S., Hesse, S. A., Ebrahim, A. M., Sullivan, K. P., Miscall, J., Richardson, J. A., Bare, S. R., Sarangi, R., Beckham, G. T., Tassone, C. J. 2026; 6 (5): 2891-2901

  Abstract

  Efficient catalytic deconstruction of plastics requires facile solvent and catalyst access to polymer substrates to minimize mass transfer effects. Autoxidation using Co-(II) acetate, Mn-(II) acetate, and a radical carrier in acetic acid is a promising strategy to deconstruct mixed plastic waste, yet the role of polymer morphology in governing solvent and catalyst accessibility remains poorly understood. Here, in situ simultaneous small- and wide-angle X-ray scattering (SAXS/WAXS), complemented by X-ray fluorescence (XRF) imaging and high-pressure differential scanning calorimetry (DSC), were used to elucidate interactions between acetic acid, a Co/Mn catalyst solution, and semicrystalline polyethylene (PE) and amorphous polystyrene (PS) from room temperature to 160 °C. In PE, acetic acid and catalyst access were confined to amorphous regions and cryomilled particle interfaces at room temperature, while crystalline lamellae remained intact after soaking for up to 34 h. Increasing temperature enabled solvent uptake into PE, followed by solvent-assisted softening above 100 °C, and a modest melting-point depression that removed lamellar transport barriers upon melting. Conversely for PS, acetic acid penetrated the glassy polymer without inducing chain mobility until the glass transition was reached, above which the observed structural changes were consistent with enhanced segmental mobility which enabled bulk penetration. These results suggest that polymer morphology and thermally activated physical transitions arising from diffusion and polymer-solvent interactions can influence whether autoxidation of plastics is transport-limited or kinetically controlled, providing a framework for aligning reaction conditions with reaction outcomes.

  View details for DOI 10.1021/jacsau.6c00230

  View details for PubMedID 42212080

  View details for PubMedCentralID PMC13213504

• Decoupled mobilization of organic carbon and nitrogen in aged wildfire ashes. Chemosphere Numan, T., Shahriar, A., Lokesh, S., Timilsina, A., Basyal, S., Raeofy, Y., Zhao, Q., Richardson, J. A., Poulson, S. R., Samburova, V., Yang, Y. 2026; 405: 144960

  Abstract

  In this work, we studied the mobility of organic carbon (OC) and nitrogen (N) in ashes and soils 2 years after major wildfires in the northern California/Nevada region (Dixie, Beckwourth, and Caldor fires) in the United States. The mobile fraction of OC ranged between 0.009 and 0.114 for ashes and 0.002 - 0.582 for background soils. The mobility of OC exhibited a significant negative correlation with the aromatic fraction in mobile OC for 2-year samples, but such correlation was not present for 0-year samples, indicating an important role of aromatic OC in its mobility after aging. The mobile fraction of N ranged 0.052 - 0.118 for ashes after 2 years. NO2- concentrations were much higher for some of 2-year samples compared to 0-year samples, indicating denitrification during the aging of ashes. The dissolved organic nitrogen (DON) mobilized from ashes after 2 years was much higher than for 0-year samples. The mobile fraction of N was not correlated with OC fraction, suggesting that for the long-term impact, mobile OC cannot be used to predict the mobile fraction of N. While the mobile fraction of OC and N were decoupled after 2 years of aging, redox reactions in OC played an important role for the mobility of OC and N. The impact of aging on the mobility of OC and N was closely related to the aromatic OC fraction in the mobile phase. Overall, 2 years after the wildfires, the total mobile OC and N in ashes and soils under ashes were higher than control soils, which raises concern for water quality and watershed function. These findings offer novel insights into the processes governing the mobilization of OC and N a few years following wildfires and the critical physicochemical properties of ashes and soils regulating the mobility of nutritional elements, OC and N.

  View details for DOI 10.1016/j.chemosphere.2026.144960

  View details for PubMedID 42127781

• Citric acid alters Arabidopsis root morphology and development through ROS-dependent and ROS-independent mechanisms. Plant physiology Zhang, T., Peng, J. T., Chu, J., Luo, S., Lee, J., Sanchez Rodriguez, D. B., Gundran, K., Xia, X., Garay-Arroyo, A., Richardson, J. A., Dickinson, A. J. 2026; 201 (1)

  Abstract

  Citric acid is an integral component of primary metabolism and cellular energetics and plays extensive roles in other cellular processes, such as signaling, chelating, and exudation. Here, we characterized the unique effects that citric acid has on Arabidopsis (Arabidopsis thaliana) root structure and development. In particular, we investigated how citric acid modifies 2 root types in opposing ways: by inhibiting primary root growth while promoting anchor root growth. To understand the mechanisms driving these different growth patterns within the same organism, we analyzed nutrient and transcriptomic responses to citric acid treatment in anchor roots and primary roots. High-spatial resolution elemental analysis revealed that root meristems and the root-hypocotyl junction are regions of strong nutrient enrichment, but that citric acid treatment has little effect on nutrient levels in these regions. Transcriptional analysis revealed major differences between primary roots and anchor roots in response to citric acid. In particular, citric acid acted as a reactive oxygen species (ROS) scavenger through increased Class III peroxidase transcription, effectively reducing H2O2 levels both in vitro and in vivo. Altering the ROS balance at the root-hypocotyl junction was sufficient to induce anchor root formation. Citric acid treatment also differentially upregulated lignin biosynthesis, lignin assembly, and ETHYLENE RESPONSE FACTOR 115 expression in primary roots and anchor roots. ETHYLENE RESPONSE FACTOR 115 regulates the quiescent center and root columella, and we found that citric acid treatment induces developmental defects in this tissue. Overall, this study reveals that a vital organic acid produced and secreted at relatively high concentrations has both widespread and specific effects on plant development and root architecture.

  View details for DOI 10.1093/plphys/kiag194

  View details for PubMedID 42160262

• Micron-scale spatial patterns of manganese oxidation states and acid phosphatase in soils under annual row crops and a native plant community SOIL SCIENCE AND PLANT NUTRITION O'Sullivan, J. B., Richardson, J., Guber, A., Kravchenko, A. 2026

  View details for DOI 10.1080/00380768.2026.2620387

  View details for Web of Science ID 001672908200001

• Accumulation of Soil Microbial Necromass Controlled by Microbe-Mineral Interactions. Environmental science & technology Zhao, Q., Bell, S., Kukkadapu, R., Richardson, J., Cliff, J., Bowden, M., Leichty, S., Hofmockel, K. S. 2025

  Abstract

  Soil organic matter (SOM) is a key reservoir for global carbon (C), supporting soil fertility and influencing greenhouse gas emissions. Microbial residues, composed of dead cells and cellular fragments, are major contributors to SOM formation. Yet, mechanisms by which minerals enhance the accumulation of microbial residues remain poorly understood. Here, we used 13C-labeled glucose in a year-long incubation to trace microbial residue in sandy and silty soils. Across both soils, approximately 89% of retained microbial 13C was recovered in the fine (<53 mum) mineral-associated organic matter (MAOM) pool. Within this pool, the light MAOM fraction, enriched in poorly crystalline Fe minerals, held 4.3 times more 13C than the heavy, phyllosilicate-dominated MAOM fraction, despite accounting for only 17.2% of the total MAOM mass and 12.3% of the total soil mass. Along with 13C enrichment, the light MAOM fraction showed greater abundance of N-containing groups, e.g., (amides and amino groups), indicative of microbial-derived compounds like proteins and amino sugars. Fe oxides in light MAOM from both soils were spatially dispersed. Microbial residue accumulation was greater in finer-textured silty soil. These findings demonstrate that mineral composition and texture jointly regulate microbial necromass accrual, highlighting light MAOM as a key pool for enhancing soil C storage.

  View details for DOI 10.1021/acs.est.5c01482

  View details for PubMedID 40705975

• Local sedimentary effects shaped key sulfur records after the Great Oxidation Event EARTH AND PLANETARY SCIENCE LETTERS Bryant, R. N., Todes, J. P., Richardson, J. A., Kalia, T. C., Prave, A. R., Lepland, A., Kirsimae, K., Blattler, C. L. 2024; 648

  View details for DOI 10.1016/j.epsl.2024.119113

  View details for Web of Science ID 001361300600001

• X-ray fluorescence and XANES spectroscopy revealed diverse potassium chemistries and colocalization with phosphorus in the ectomycorrhizal fungus Paxillus ammoniavirescens FUNGAL BIOLOGY Richardson, J. A., Rose, B. D., Garcia, K. 2024; 128 (6): 2054-2061

  Abstract

  Ectomycorrhizal (ECM) fungi play a major role in forest ecosystems and managed tree plantations. Particularly, they facilitate mineral weathering and nutrient transfer towards colonized roots. Among nutrients provided by these fungi, potassium (K) has been understudied compared to phosphorus (P) or nitrogen (N). The ECM fungus Paxillus ammoniavirescens is a generalist species that interacts with the root of many trees and can directly transfer K to them, including loblolly pine. However, the forms of K that ECM fungi can store is still unknown. Here, we used synchrotron potassium X-ray fluorescence (XRF) and K-edge X-ray Absorption Near Edge Structure (XANES) spectroscopy on P. ammoniavirescens growing in axenic conditions to investigate the K chemistries accumulating in the center and the edge of the mycelium. We observed that various K forms accumulated in different part of the mycelium, including K-nitrate (KNO3), K-C-O compounds (such as K-tartrate K2(C4H4O6) and K-oxalate (K2C2O4)), K-S and K-P compounds. Saprotrophic fungi have been shown to excrete carboxylic acids, which in turn play a role in soil mineral weathering. Our finding of several K counter-ions to carboxylic acids may suggest that, besides their direct transfer to colonized roots, K ions can also be involved in the production of compounds necessary for sourcing nutrients from their surrounding environment by ECM fungi. Additionally, this work reveals that XANES spectroscopy can be used to identify the various forms of K accumulating in biological systems.

  View details for DOI 10.1016/j.funbio.2024.08.004

  View details for Web of Science ID 001294580100001

  View details for PubMedID 39174240

• Sulfur isotopes from the Paleoproterozoic Francevillian Basin record multigenerational pyrite formation, not depositional conditions COMMUNICATIONS EARTH & ENVIRONMENT Paiste, K., Fike, D. A., Mayika, K., Moussavou, M., Lepland, A., Prave, A. R., Sato, T., Ueno, Y., Sawaki, Y., Richardson, J. A., Wood, R. S., Jones, C., Webb, S. M., Kirsimae, K. 2024; 5 (1)

  View details for DOI 10.1038/s43247-024-01498-1

  View details for Web of Science ID 001249172200003

• X-ray absorption spectroscopy and theoretical investigations of the effect of extended ligands in potassium organic matter interaction. The Journal of chemical physics Richardson, J. A., Kim, H., Kas, J. J., You, X., Andersen, A., Ginovska, B., Bhattacharjee, A., Sarangi, R. 2024; 160 (4)

  Abstract

  Potassium (K) is an essential nutrient for plant growth, and despite its abundance in soil, most of the K is structurally bound in minerals, limiting its bioavailability and making this soil K reservoir largely inaccessible to plants. Microbial biochemical weathering has been shown to be a promising pathway to sustainably increase plant available K. However, the mechanisms underpinning microbial K uptake, transformation, storage, and sharing are poorly resolved. To better understand the controls on microbial K transformations, we performed K K-edge x-ray absorption near-edge structure (XANES) spectroscopy on K-organic salts, including acetate, citrate, nitrate, oxalate, and tartrate, which are frequently observed as low molecular weight organic acids secreted by soil microbes, as well as humic acid, which acts as a proxy for higher molecular weight organic acids. The organic salts display feature-rich K XANES spectra, each demonstrating numerous unique features spanning 13eV range across the absorption edge. In contrast, the spectra for humic acid have one broad, wide feature across the same energy range. We used a combination of time-dependent density functional theory and the Bethe-Salpeter equation based approach within the OCEAN code to simulate the experimental spectra for K-nitrate (KNO3) and K-citrate [K3(C6H5O7)·H2O] to identify the electronic transitions that give rise to some of the outlying and unique spectral features in the organic salts. KNO3 has both the lowest and highest lying energy features, and K3(C6H5O7)·H2O is produced by several soil microbes and is effective at mineral weathering. Our results analyze the K-organic salt bonding in detail to elucidate why the spectral shapes differ and indicate that the K K-edge XANES spectra are associated with the entire ligand despite similar first-shell bonding environments around the K center. The improved understanding of K bonding environments with organic ligands and their use for interpretation of the K-XANES spectra provides an important toolkit to understand how K is transformed by microbial processes and made bioavailable for plant uptake.

  View details for DOI 10.1063/5.0183603

  View details for PubMedID 38284657

• Fungal organic acid uptake of mineral-derived K is dependent on distance from carbon hotspot. mBio Bhattacharjee, A., Velickovic, D., Richardson, J. A., Couvillion, S. P., Vandergrift, G. W., Qafoku, O., Taylor, M. J., Jansson, J. K., Hofmockel, K., Anderton, C. R. 2023: e0095623

  Abstract

  Fungal mineral weathering regulates the bioavailability of inorganic nutrients from mineral surfaces to organic matter and increase the bioavailable fraction of nutrients. Such weathering strategies are classified as biomechanical or biochemical. In the case of fungal uptake of mineral nutrients through biochemical weathering, it is widely hypothesized that uptake of inorganic nutrients occurs through organic acid chelation, but such processes have not been directly visualized. This is in part due to challenges in probing the complex and heterogeneous soil environment. Here, using an epoxy-based, mineral-doped soil micromodel platform, which emulates soil mineralogy and porosity, we visualize the molecular mechanisms of mineral weathering. Mass spectrometry imaging revealed differences in the distribution of fungal exudates, citric acid, and tartaric acid on the soil micromodels in presence of minerals. Citric acid was detected closer to the nutrient-rich inoculation point, whereas tartaric acid was highly abundant away from inoculation point. This suggested that the organic acid exuded by the fungi depended on the proximity from the carbon-rich organic substrate at the point of inoculation. Using a combination of X-ray fluorescence and X-ray near edge structure analysis, we identified citric acid- and tartaric acid-bound K within fungal hyphae networks grown in the presence of minerals. Combined, our results provide direct evidence that fungi uptake and transport mineral derived nutrient organic acid chelation. The results of this study provided unprecedented visualization of fungal uptake and transport of K+, while resolving the indirect weathering mechanism of fungal K uptake from mineral interfaces. IMPORTANCE Fungal species are foundational members of soil ecosystems with vital contributions that support interspecies resource translocation. The minute details of these biogeochemical processes are poorly investigated. Here, we addressed this knowledge gap by probing fungal growth in a novel mineral-doped soil micromodel platform using spatially-resolved imaging methodologies. We found that fungi uptake K from K-rich minerals using organic acids exuded in a distance-dependent manner from a carbon-rich hotspot. While identification of specific mechanisms within soil remains challenging, our findings demonstrate the significance of reduced complexity platforms such as the mineral-doped micromodel in probing biogeochemical processes. These findings provide visualization into hyphal uptake and transport of mineral-derived nutrients in a resource-limited environment.

  View details for DOI 10.1128/mbio.00956-23

  View details for PubMedID 37655873

• Saprotrophic Fungus Induces Microscale Mineral Weathering to Source Potassium in a Carbon-Limited Environment MINERALS Richardson, J. A., Anderton, C. R., Bhattacharjee, A. 2023; 13 (5)

  View details for DOI 10.3390/min13050641

  View details for Web of Science ID 000996976100001

• Tonian Carbonates Record Phosphate-Rich Shallow Seas GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS Roest-Ellis, S., Richardson, J. A., Phillips, B. L., Mehra, A., Webb, S. M., Cohen, P. A., Strauss, J. V., Tosca, N. J. 2023; 24 (5)

  View details for DOI 10.1029/2023GC010974

  View details for Web of Science ID 000999805900001

• A Mineral-Doped Micromodel Platform Demonstrates Fungal Bridging of Carbon Hot Spots and Hyphal Transport of Mineral-Derived Nutrients. mSystems Bhattacharjee, A., Qafoku, O., Richardson, J. A., Anderson, L. N., Schwarz, K., Bramer, L. M., Lomas, G. X., Orton, D. J., Zhu, Z., Engelhard, M. H., Bowden, M. E., Nelson, W. C., Jumpponen, A., Jansson, J. K., Hofmockel, K. S., Anderton, C. R. 2022: e0091322

  Abstract

  Soil fungi facilitate the translocation of inorganic nutrients from soil minerals to other microorganisms and plants. This ability is particularly advantageous in impoverished soils because fungal mycelial networks can bridge otherwise spatially disconnected and inaccessible nutrient hot spots. However, the molecular mechanisms underlying fungal mineral weathering and transport through soil remains poorly understood primarily due to the lack of a platform for spatially resolved analysis of biotic-driven mineral weathering. Here, we addressed this knowledge gap by demonstrating a mineral-doped soil micromodel platform where mineral weathering mechanisms can be studied. We directly visualize acquisition and transport of inorganic nutrients from minerals through fungal hyphae in the micromodel using a multimodal imaging approach. We found that Fusarium sp. strain DS 682, a representative of common saprotrophic soil fungus, exhibited a mechanosensory response (thigmotropism) around obstacles and through pore spaces (~12mum) in the presence of minerals. The fungus incorporated and translocated potassium (K) from K-rich mineral interfaces, as evidenced by visualization of mineral-derived nutrient transport and unique K chemical moieties following fungus-induced mineral weathering. Specific membrane transport proteins were expressed in the fungus in the presence of minerals, including those involved in oxidative phosphorylation pathways and the transmembrane transport of small-molecular-weight organic acids. This study establishes the significance of a spatial visualization platform for investigating microbial induced mineral weathering at microbially relevant scales. Moreover, we demonstrate the importance of fungal biology and nutrient translocation in maintaining fungal growth under water and carbon limitations in a reduced-complexity soil-like microenvironment. IMPORTANCE Fungal species are foundational members of soil microbiomes, where their contributions in accessing and transporting vital nutrients is key for community resilience. To date, the molecular mechanisms underlying fungal mineral weathering and nutrient translocation in low-nutrient environments remain poorly resolved due to the lack of a platform for spatial analysis of biotic weathering processes. Here, we addressed this knowledge gap by developing a mineral-doped soil micromodel platform. We demonstrate the function of this platform by directly probing fungal growth using spatially resolved optical and chemical imaging methodologies. We found the presence of minerals was required for fungal thigmotropism around obstacles and through soil-like pore spaces, and this was related to fungal transport of potassium (K) and corresponding K speciation from K-rich minerals. These findings provide new evidence and visualization into hyphal transport of mineral-derived nutrients under nutrient and water stresses.

  View details for DOI 10.1128/msystems.00913-22

  View details for PubMedID 36394319

• Distribution of Mn Oxidation States in Grassland Soils and Their Relationships with Soil Pores ENVIRONMENTAL SCIENCE & TECHNOLOGY Kravchenko, A. N., Richardson, J. A., Lee, J., Guber, A. K. 2022; 56 (22): 16462-16472

  View details for DOI 10.1021/acs.est.2c0540316462

  View details for Web of Science ID 000885927100001

• Distribution of Mn Oxidation States in Grassland Soils and Their Relationships with Soil Pores. Environmental science & technology Kravchenko, A. N., Richardson, J. A., Lee, J. H., Guber, A. K. 2022

  Abstract

  Manganese (Mn) is known to be an active contributor to processing and cycling of soil organic carbon (C), yet the exact mechanisms behind its interactions with C are poorly understood. Plant diversity in terrestrial ecosystems drives feedback links between plant C inputs and soil pores, where the latter, in turn, impact the redox environment and Mn. This study examined associations between soil pores (>36 mum O) and Mn within intact soils from two grassland ecosystems, after their >6-year implementation in a replicated field experiment. We used mu-XRF imaging and XANES spectroscopy to explore spatial distribution patterns of Mn oxidation states, combined with X-ray computed microtomography and 2D zymography. A high plant diversity system (restored prairie) increased soil C and modified spatial distribution patterns of soil pores as compared to a single species system (monoculture switchgrass). In switchgrass, the abundance of oxidized and reduced Mn oxidation states varied with distance from pores consistently with anticipated O2 diffusion, while in the soil from restored prairie, the spatial patterns suggested that biological activity played a greater role in influencing Mn distributions. Based on the findings, we propose a hypothesis that Mn transformations promote C gains in soils of high plant diversity grasslands.

  View details for DOI 10.1021/acs.est.2c05403

  View details for PubMedID 36268932

• Characterization and Geological Implications of Precambrian Calcite-Hosted Phosphate GEOPHYSICAL RESEARCH LETTERS Richardson, J. A., Roest-Ellis, S., Phillips, B. L., Strauss, J., Webb, S. M., Tosca, N. J. 2022; 49 (17)

  View details for DOI 10.1029/2022GL100328

  View details for Web of Science ID 000855084300001

• The source of sulfate in brachiopod calcite: Insights from mu-XRF imaging and XANES spectroscopy CHEMICAL GEOLOGY Richardson, J. A., Newville, M., Lanzirotti, A., Webb, S. M., Rose, C., Catalano, J. G., Fike, D. A. 2019; 529

  View details for DOI 10.1016/j.chemgeo.2019.119328

  View details for Web of Science ID 000496914900016

• Depositional and diagenetic constraints on the abundance and spatial variability of carbonate-associated sulfate CHEMICAL GEOLOGY Richardson, J. A., Newville, M., Lanzirotti, A., Webb, S. M., Rose, C., Catalano, J. G., Fike, D. A. 2019; 523: 59–72

  View details for DOI 10.1016/j.chemgeo.2019.05.036

  View details for Web of Science ID 000480333200006

• Insights into past ocean proxies from micron-scale mapping of sulfur species in carbonates GEOLOGY Rose, C., Webb, S. M., Newville, M., Lanzirotti, A., Richardson, J. A., Tosca, N. J., Catalano, J. G., Bradley, A. S., Fike, D. A. 2019; 47 (9): 833–37

  View details for DOI 10.1130/G46228.1

  View details for Web of Science ID 000483606500011