Efficient U(VI) immobilization of uranium-contaminated soil mediated by Fungal-Bacterial Consortia

This study isolated and screened four uranium-tolerant bacterial strains (Priestia aryabhattai, Priestia megaterium, Bacillus subtilis, Arthrobacter woluwensis) and a group of uranium-tolerant symbiotic fungi (Mucor lusitanicus, Mucor ambiguus, Mucor circinelloides, Mucor plumbeus, Rhizopus arrhizus, Parasitella parasitica) from uranium-contaminated soil, based on which a Fungal-Bacterial Consortia (FBC) was constructed. The uranium immobilization performance of two FBC application modes in soil, namely direct addition and sodium alginate immobilization, was systematically evaluated. The results showed that uranium immobilization by FBC was mainly achieved via biosorption, bioreduction and bioaccumulation. Application of free FBC at 5% dosage and sodium alginate-immobilized FBC beads at 3% dosage reduced the acid-soluble uranium fraction by 65% and increased the residual uranium fraction by approximately 533%, with remediation performance significantly superior to that of single microbial strains. Furthermore, FBC amendment significantly elevated the abundance of functional strains in soil, with notable enrichment of the core uranium-tolerant genera screened in this study, including Bacillus, Arthrobacter, Priestia and Mucor. Further analyses demonstrated that the activities of soil urease, dehydrogenase and sucrase were significantly enhanced following FBC treatment, coupled with a marked upregulation in the expression of functional genes nirS3 and phnK. In addition, for Lolium perenne cultivated in the remediated soil, plant height, root length and biomass were increased by 30-50%, and uranium accumulation efficiency of the root system was enhanced by 3 folds. Collectively, these findings validate the high-efficiency remediation potential of the self-constructed uranium-tolerant FBC and provide a practical foundation for in-situ bioremediation strategies.