Microbial-Mediated Differential Regulation of Yttrium Behavior in the Rhizosphere: Blocking Uptake in Lactuca sativa L. While Enhancing Bioavailability in Solanum nigrum L.

To address yttrium (Y) contamination from ion adsorption mining, this study developed a combined microbial phytoremediation strategy for dual objectives: ensuring crop safety in Lactuca sativa and enhancing Y recovery by Solanum nigrum. Two specific microbial consortia were constructed from rare earth tailings isolates: inoculant I (bacterial: Enterobacter sp., Serratia sp., Bacillus sp.) applied to L. sativa, and inoculant II (fungal: Penicillium sp., Aspergillus sp., Talaromyces sp.) applied to S. nigrum. Inoculant I increased L. sativa biomass by 26% while reducing Y content in roots and rhizosphere soil solution by 47% and 56%, respectively, potentially through down-regulation of amino acid metabolites. Inoculant II increased Y content in the S. nigrum rhizosphere soil solution by 89%, linked to up-regulation of organic acids and coumarin derivatives. Both consortia reduced plant stress markers and enhanced soil enzyme activities. These findings demonstrate that specialized microbial consortia can differentially regulate Y behavior in the rhizosphere—immobilizing it in a crop for food safety, while enhancing its bioavailability for a hyperaccumulator—offering a targeted strategy for managing rare earth element-contaminated agricultural soils.