Assessing putative biomagnetite formation in a natural hardwood-forest soil
EMSL Project ID
51465
Abstract
Fungi play a fundamental role in regulating and accelerating the cycling of nutrients (C, N, S) and metals (Ca, Na, Mg, K, Fe, Mn) bound in soil minerals and rocks as demonstrated by the ubiquitous nature of fungal-derived tunnels, pits, and etch patterns on the surfaces of mineral grains. The precise mechanisms whereby microorganisms biosense and access specific minerals through (in)direct weathering pathways remains an ongoing topic of research as do the formation pathways for biominerals produced by fungi in the soil environment. Our team is in the process of finalizing a manuscript based on the work described herein which focuses on understanding the biotic vs. abiotic pathways of mineral weathering and secondary mineral precipitation in granular substrates deployed in a natural mixed hardwood forest soil environment for three years. Grain-microbe interfaces were interrogated using a suite of electron microscopy techniques coupled with bulk XRD analyses. The data sets present a compelling story; however, this limited scope proposal will support one month of additional experimental work that will greatly extend the findings from an EMSL science theme user proposal (49828-Rebecca Lybrand, OSU-PI) that was finalized and closed at the end of FY19. This proposal contains three overarching research objectives: Objective 1: Collect a small subset of statistical data using Scanning Electron Microscopy (SEM) to support the finding that the secondary mineralization of magnetite observed at the surface and near-surface of a pyroxene grain resulted from biogenic processes by fungi adhered to the mineral grain (Fig. 1).
Objective 2: Employ Atomic Probe Tomography (APT) to assess the elemental composition and morphology of the putative biomagnetite observed adjacent to fungal-mineral interfaces as evidence for biogenic signatures.
Objective 3: Perform measurements with NanoSIMS to determine the isotopic compositions (i.e., ?56Fe, ?57Fe; ?47Ti, ?49Ti) of magnetite grains to gain insights on abiotic or biotic formation pathways, such that abiotic processes will show high temperature inclusions whereas biotic formation will present low temperature precipitation.
Identifying the processes that drive mineral weathering is critical to addressing the global challenge of climate change, particularly fungal-driven mineral transformation and biomineral formation mechanisms that are underrepresented or excluded from models of rock-derived nutrient cycling. This proposal includes SEM automated mineral grain identification and characterization of secondary precipitates, APT analysis to assess the characteristics of secondary minerals formed on grain surfaces, and NanoSIMS to measure the isotopic ratio of secondary minerals. Collectively, these activities will offer insight on the processes (biotic or abiotic) that lead to formation of Fe-rich secondary minerals.
Project Details
Project type
Limited Scope
Start Date
2020-07-10
End Date
2020-09-09
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Lybrand, R.A., Qafoku, O., Bowden, M.E. et al. Fungal hyphae develop where titanomagnetite inclusions reach the surface of basalt grains. Sci Rep 12, 3407 (2022). https://doi.org/10.1038/s41598-021-04157-z.