Application potential of phosphate-solubilizing microorganisms for remediating HMs-PAHs co-contaminated soils:...

Microbial remediation is a cost-effective and environmentally friendly approach for soils co-contaminated with polycyclic aromatic hydrocarbons (PAHs) and heavy metals (HMs). However, the role of microbial phosphorus metabolism in co-contaminant removal remains poorly understood. In this study, three chromium (Cr)-tolerant and phosphate-solubilizing strains (Aspergillus-HP2, Talaromyces-C1, and Pseudomonas-PJ1) isolated from PAH-degrading enrichments were assembled into a fungal-bacterial consortium (BF) based on pyrene removal efficiency and cell surface hydrophobicity. Microcosm experiments showed that BF removed 36.36 % of pyrene and 19.50 % of Cr(VI) within 7 d, whereas biochar immobilization increased removal efficiencies to 61.06 % and 92.80 %, respectively. Integrated metabolic phenotype analyses indicated that phosphorus availability directly enhanced pyrene and Cr(VI) removal by promoting phosphorus mobilization and enzymatic activity, whereas biochar immobilization indirectly improved degradation by stabilizing extracellular interfaces and system-level metabolic networks. In 40-day soil trials, 3 % (w/w) biochar-immobilized BF (IBF) achieved higher removal of pyrene (35.61 mg·kg^-1) and Cr(VI) (393.52 mg·kg^-1) than biochar alone or free-cell inoculation. Microbial analyses further revealed that IBF enriched indigenous functional microorganisms and increased the abundance of core PAH-degradation and phosphate-solubilization genes, thereby facilitating pyrene degradation and Cr(VI) detoxification. Overall, this study presents a low-toxicity and effective strategy for microbial remediation of soils co-contaminated with PAHs and HMs.