Microbial community succession in response to in-situ coordinated leaching of ion-adsorption rare earth ores.

The stable supply of medium and heavy rare earth elements (M-HREEs) is vital for sustainable development in strategic sectors including permanent magnets, phosphors, and metallurgy. Southern China's ion-adsorption rare earth deposits represent the world's primary M-HREE source. However, the dominant extraction technique, which employs in-situ leaching with ammonium sulfate via an ion-exchange mechanism, has caused severe ammonia-nitrogen pollution in mining regions. To overcome this environmental challenge, our team developed an innovative non-contact bioleaching process based on coordination-elution principles and successfully implemented a 2000-ton industrial-scale in-situ leaching trial. In this study, we systematically analyzed the impact of coordinated leaching on microbial communities across different ore depths using 16S rDNA amplicon sequencing. Results revealed significant shifts in dominant bacterial phyla after leaching. In shallow ore layers, Proteobacteria were replaced by Chloroflexi and Acidobacteriota, whereas in deep layers, Proteobacteria shifted to Firmicutes. This ecological succession was accompanied by a significant enhancement in the degradation capacity for simple carbon sources, which is expected to effectively mitigate the issue of leaching agent residue. Microbial co-occurrence networks in shallow layers experienced more pronounced disruption, showing sparser connections and weakened species interactions. Furthermore, the decline in rare earth content after leaching suppressed methanol metabolism in deep layers, as indicated by significant downregulation of genes encoding the MxaFI-MDH protein. This work establishes a scientific foundation for enhancing environmental risk assessment protocols aimed at green mining of ion-adsorption rare earth ores and offers meaningful guidance for advancing sustainability in the rare earth industry.