Decoding pyrene-induced reactive oxygen species production in the rhizosphere and their role in biodegradation: The repair mechanism of symbiotic driving by Fe(II) and microorganisms.

Reactive oxygen species (ROS) are considered key drivers of biogeochemical processes. However, there is limited research on the factors influencing ROS generation in the rhizosphere due to polycyclic aromatic hydrocarbon (PAHs) pollution during plant-microbe joint remediation, as well as their role in biodegradation. This study demonstrated that exposure to pyrene at a concentration of 100 mg/kg significantly enhanced the release of hydrogen peroxide (H₂O₂), hydroxyl radicals (•OH), and superoxide anions (O₂•⁻) in the rhizosphere of ryegrass during root development. The concentrations of these reactive oxygen species were 1.5-7.8 times higher than those in the control group. Additionally, the Fe(II) concentration increased by 37.5 ± 3.2 %, and the pyrene degradation rate reached 26.8 ± 1.4 %. These results indicate that pyrene serves as a major factor stimulating ROS generation in ryegrass. Among these processes, Fe(II) catalyzes the production of •OH, which directly attacks the benzene ring structure of pyrene. High-throughput analysis further revealed that ROS enhanced the diversity, cohesion, and robustness of the rhizosphere microbial community structure. Furthermore, Pseudomonas, Marmoricola, Nocardioides and Dietzia were identified as core microbial genera involved in pyrene degradation and ecological restoration. Metagenomics analysis suggests that rhizosphere microorganisms respond to ROS-induced oxidative stress by enhancing ATP synthesis, which provides energy for antioxidant-related protein production and damage repair, thereby accelerating pyrene degradation. These results elucidate the ROS-mediated driving mechanism behind microbial pyrene degradation in plant-microbe combined remediation systems, thereby providing a theoretical basis for optimizing bioremediation strategies for organically contaminated soils.