Synthetic microbial community shields wheat from cadmium: Coordinating host metabolic reprogramming and rhizosphere...

Mitigating cadmium (Cd) accumulation in staple crops like wheat (Triticum aestivum L.) is essential for public health. While plant growth-promoting rhizobacteria offer a sustainable solution, the mechanistic synergy of synthetic microbial communities (SynComs) remains poorly elucidated. Here, we developed a binary SynCom_CB (Pantoea sp. C15 and Bacillus sp. B21) that exhibited a synergistic Cd^2 + immobilization capacity (81.15%), significantly outperforming individual strains. SynCom_CB established an extracellular shield and reduced wheat Cd accumulation by 32.2% (shoots) and 48.1% (roots). Integrated multi-omics revealed that SynCom_CB induced coordinated metabolic reprogramming associated with improved Cd stress tolerance: the activation of stilbenoid, diarylheptanoid, and gingerol biosynthesis might enhance antioxidant capacity, while enhanced propanoate metabolism potentially supported energy supply for Cd detoxification. Specifically, SynCom_CB coordinated the expression of Cd uptake, transport, efflux, vacuolar segregation, and cell wall biosynthesis genes, optimizing Cd sequestration in cell walls and restricting its translocation to sensitive organelles in roots. Furthermore, SynCom_CB effectively regulated the rhizosphere microenvironment by increasing soil pH, decreasing available Cd, and inducing treatment-specific abundance shifts in key taxa (Actinobacteriota and Firmicutes). Finally, field plot experiment demonstrated that SynCom_CB effectively improved agronomic traits, increased grain yield by 8.74%, and reduced grain Cd concentrations by 46.59%. Overall, this study provides a theoretical framework for the application of SynComs to efficiently reduce Cd accumulation in wheat.