Abstract
Uranium (U) mining causes severe radioactive contamination threatening ecosystems. Biological soil crusts (BSCs), as pioneer communities in degraded habitats, show strong heavy metal accumulation potential, yet their adaptive mechanisms under U stress remain unclear. In this study, BSCs from a uranium tailings dam in Hunan Province were exposed to simulated U stress. Results showed that BSCs exhibited exceptionally high U accumulation capacity (up to 4131 mg/kg), and effectively immobilised U by converting it into residual and organic‐bound fractions (collectively > 70%) via carboxyl complexation and microbial mineralisation, thus significantly reducing environmental mobility. U stress caused damage to the photosynthetic and antioxidant systems of the BSCs. Microbial community complexity decreased, with tolerant taxa including Proteobacteria and Bacilli significantly enriched. Metagenomics revealed distinct cross‐kingdom functional adaptation strategies: bacteria upregulated energy metabolism and acetaldehyde metabolism to facilitate efflux detoxification, while fungi strengthened lipid homeostasis and antioxidant metabolism. Several U‐tolerant strains ( Bacillus, Aspergillus and Penicillium ) closely associated with U immobilisation were further isolated and verified. This study systematically reveals the synergistic tolerance mechanisms of BSCs under U stress and provides key microbial resources and theoretical support for the in situ bioremediation of U‐contaminated sites.