Glomalin related soil protein enhances the capacity of PAH natural attenuation in soils through modulation of soil organic matter and microbiota

Soil contamination by polycyclic aromatic hydrocarbons (PAHs) remains a widespread concern. Glomalin-related soil protein (GRSP), a notable soil organic component secreted by arbuscular mycorrhizal fungi, contributes positively to soil carbon sequestration. While its influence on the fate of inorganic pollutants has been recognized, the specific mechanisms by which GRSP regulates PAHs in soil are still poorly understood. Therefore, this study investigated how GRSP strengthens PAH natural attenuation in contaminated soil through a microcosm experiment, combined with sequential SOM fractionation and high-throughput sequencing. Our results demonstrated that GRSP significantly promoted PAH attenuation, with the removal of phenanthrene and pyrene increasing by 0.09%-1.03% and 1.66%-73.40%, respectively. GRSP addition directly and indirectly increased the content of key SOM components, including humic acid, fulvic acid and dissolved organic matter, thereby altering PAH distribution in soil. Meanwhile, high-throughput sequencing and functional gene predictions analyses further revealed that GRSP enriched indigenous PAH-degrading bacteria (e.g., Massilia, Gemmatimonas, and Mycobacterium) and increased functional genes (e.g., nidA, phe) copy number, ultimately facilitating PAH removal via the protocatechuic acid pathway. These findings clarify the auxiliary role of GRSP in PAH remediation and propose a novel strategy for enhancing soil self-remediation through the management of GRSP level or AMF activity.