Engineering rhizosphere microbial consortia for soil bioremediation: Mechanisms, field constraints, and evidence-based design

Soil contamination continues to threaten ecosystem health and agricultural productivity worldwide. However, rhizosphere-mediated bioremediation has emerged as a nature-inspired, sustainable approach for mitigating these impacts. This review advocates field-scale implementation of rhizosphere microbiome engineering by exploiting interactions among plants, microorganisms, and soil. Unlike previous reviews that primarily summarize rhizosphere-mediated remediation processes, it integrates mechanistic, ecological, and engineering perspectives to identify critical barriers limiting field performance. This review synthesizes recent advances in rhizosphere microbiome engineering, with an emphasis on root-exudate manipulation, synthetic microbial communities (SynComs), biochar-assisted remediation, and multi-omics technologies. The evidence reviewed indicates that root exudates are key regulators of microbial recruitment, biofilm formation, and expression of contaminant-degrading genes, while engineered microbial consortia enhance functional complementarity and pollutant transformation. A comparative analysis of laboratory and field studies reveals substantial performance gaps, with highly efficient degradation observed under controlled conditions often declining following field deployment because of microbial competition, environmental variability, and contaminant sorption dynamics. The review further shows that integration of SynComs with biochar carriers and precision root-exudate engineering can improve microbial establishment and remediation efficiency. Advances in metagenomics, metabolomics, and systems biology are enabling more predictive design and monitoring of rhizosphere processes. Collectively, this review provides a mechanistic synthesis, identifies key translational bottlenecks, and outlines practical directions for developing scalable rhizosphere-based remediation technologies.