Signal-guided microbial communities enhance the entrapment of rare earth elements

Quorum sensing (QS) has important consequences for the productivity and stability of microbial communities, determining community function. Microbial communities in nature often exist in the pattern of multi-species microbial aggregates, but the ecological roles of QS in aggregates are poorly understood due to the aggregates' heterogeneity and complexity, in particular the entrapment of rare earth elements (REEs) from waste streams. Using periphytic biofilm (PB) as a microbial-aggregate model, we addressed how QS via acyl-homoserine-lactones (AHLs) regulated REEs entrapment. The REEs entrapment capacity of AHLs-enhanced PBs were improved by ∼ 2x compared to native PBs, with entrapment efficiencies up to ∼ 96 %, which was feasible in real-world waste streams including mine wastewater, e-waste and coal fly ash. AHLs promoted the synthesis and sharing of biopolymers, which facilitated REEs entrapment by electrostatic interaction, proton release and complex precipitation. AHLs addition optimized the acid-tolerant community and reduced the damage to PB caused by pH and REEs stress using the protective barrier mechanism of extracellular biopolymers. The successful field-scale implementation of this strategy provides a green and feasible path for a circular economy of REEs.