Intricate interactions between plant roots, fungi, and soil microbes, within mutualistic mycorrhizal communities, underpin plant health and ecosystem resilience by mediating nutrient exchange. Despite identification of key microbial genera involved in these mutualisms, the spatial and molecular architecture driving these interactions remains largely unresolved. Here, we develop and apply cryogenic electron tomography (cryo-ET) and confocal microscopy methods to visualize multi-species interactions at nanoscale resolution using field-derived fungal and bacterial isolates from forest ecosystems. We consistently observed mutualistic Burkholderia association with the periphery of fungal hyphae and release of extracellular vesicles (EVs) mediating communication between microbial partners. We isolate, image and characterize EV contents using cryo-EM and omics approaches to uncover the molecular underpinning this dialogue. Our findings reveal the structural details of fungal-bacterial interactions during symbiosis that contribute to forest carbon cycling and ecosystem resilience under environmental stress.
Ansell et al. (Sun,) studied this question.