Species-specific and physiological states of rhizosphere bacteria drive heavy metal remediation

Microbial fixation of heavy metals are essential for environmental remediation, but the role of species specificity and physiological states in passivation remain unclear, limiting effective strategy development. In this study, we systematically isolated 18 rhizosphere species through pot enrichment and trait-based metabolic screening to evaluate their metal stabilization profiles. Bacillales demonstrated a peak adsorption of 154 mg/g (mean: 59 mg/g) through surface binding, which accounted for 88% of the total metal removal, underscoring its potential for repeated applications. Pseudomonadales enhanced metal fixation by 12–42% through biofilm formation, while Burkholderiales achieved 2-45% metal precipitation via urease-driven mineralization. Critically, viable cells reduced metal re-release risk by 23% compared to non-viable counterparts, highlighting physiological state impacts. By leveraging these microbial properties, we achieved nearly 100% heavy metal removal using a three-stage synergistic batch reactor and reduced metal accumulation in rice hydroponics by 52%. The global distribution of these three bacterial types (mean 11.6%, maximum: 74.4%) highlights their intrinsic adaptability to diverse geo-climatic conditions, supporting their potential for region-specific remediation. Validation in metal-contaminated soils further underscores their crucial role in metal passivation. These findings provide a mechanistic framework for designing tailored rhizosphere bacterial consortia and offer valuable insights into precision bioremediation strategies.