Organic phosphorus activation by functional bacterial consortium promotes lead immobilization in contaminated soil

Microbial remediation of lead (Pb)-contaminated soil through phosphate-mediated stabilization is often hindered by limited microbial stress tolerance and phosphorus availability. To address these limitations, directional enrichment, microcosm experiments, high-throughput sequencing, and functional gene microarray analysis were combined to develop a composite functional consortium with Pb tolerance and phosphate-solubilizing capacity. The results revealed that the co-enrichment strategy produced a composite functional consortium with strong Pb resistance and high capacities for inorganic phosphorus solubilization and organic phosphorus mineralization. After inoculation, soil acid phosphatase and phytase activities significantly increased, thereby promoting organic phosphorus activation and Pb immobilization. Moreover, Pb leachability, mobility, and bioaccessibility decreased by 50%, 67%, and 55%, respectively, relative to their corresponding initial values on day 0. Functional gene microarray analysis revealed a significant decrease in pbrT abundance and enrichment of genes associated with the czc efflux system, cadA, and mobile genetic elements. This pattern suggests a potential shift in microbial Pb resistance strategies from intracellular uptake to extracellular efflux. Partial least squares path modeling further revealed distinct but complementary association patterns among microbial guilds. Specifically, passivators were mainly associated with phosphorus-mediated Pb stabilization, while tolerators were more closely linked to Pb-stress adaptation and extracellular polymeric substance-mediated Pb binding. These findings provide a theoretical basis for microbiome-based remediation of heavy metal-contaminated soils using native organic phosphorus pools.