Biochar nanoparticles modulate root-associated microbial interactions under polycyclic aromatic hydrocarbon stress

Polycyclic aromatic hydrocarbons (PAHs) are persistent soil contaminants that impose chronic stress on plants and their associated root microbiota. However, how plants and root-associated microbial communities reorganize their interactions under PAH stress, and how these processes can be modulated by carbon-based amendments, remains insufficiently understood. We employed a controlled hydroponic system as a mechanistic model to investigate how biochar nanoparticles influence plant performance and root-associated microbial assembly under PAH exposure. Biochar nanoparticle addition significantly alleviated PAH-induced phytotoxicity, accompanied by pronounced shifts in root-associated microbial community structure, network topology, and functional potential. Network analysis revealed enhanced microbial connectivity and stability, while lipidomic profiling indicated coordinated changes in root-associated metabolic pathways linked to stress adaptation. These responses suggest that biochar nanoparticles act as regulators of root-associated processes rather than serving solely as passive sorbents, reshaping plant-microbe interactions under chemical stress. Our findings demonstrate that, in this hydroponic system, nanoscale biochar can modulate plant-root microbe interactions under PAH stress through the combined effects of PHE adsorption and modulation of root-associated (surface-attached) microbial communities. By disentangling particle-driven processes from soil complexity, this work establishes a mechanistic framework for understanding nanoscale biochar-plant-microbe interactions under PAH stress, opening new avenues for water-based phytoremediation and rational design of nanoscale soil amendments.