Assessing fungal–mineral interactions in soil: A review of microscale methods

Abstract

Biological weathering of minerals has profoundly transformed Earth over geologic time by driving soil formation, nutrient cycling, and long-term biogeochemical processes. Among soil biota, fungi are increasingly recognized as key yet obscure drivers of weathering through their unique hyphal growth forms, metabolic capabilities, and symbiotic associations with plants and other microorganisms. This review synthesizes current understanding of fungal–mineral interactions across scales, from microscale hyphal–mineral interfaces to landscape and global implications. We begin with the evolutionary history of fungi and explore physical and chemical aspects of fungal weathering, including biophysical penetration, organic acid production, biomineral formation, and mineral sensing capabilities. We further assess traditional and emerging methodologies for studying fungal–mineral interactions, encompassing microscopy (scanning electron, transmission electron, helium ion, and atomic force), x-ray-based analyses (computed tomography; x-ray diffraction; energy dispersive, fluorescence, and adsorption spectroscopies), geochemical analyses (sequential extractions and mass spectrometry), molecular tools (amplicon and metagenomic sequencing), and lab- and field-based experimental design considerations. Finally, we discuss future research directions, including applications for enhanced silicate weathering, climate modeling, and material and extraterrestrial sciences. By exploring the outstanding questions and challenges of fungal weathering research, we emphasize the need for quantitative, cross-scale research to constrain fungal contributions to past, present, and future environmental change.