Bioaugmentation with Paenarthrobacter nitroguajacolicus G1-N1A accelerates atrazine remediation, modulates soil bacterial communities, and alleviates phytotoxicity in common bean.

Atrazine, widely applied in maize fields, exhibits strong stability and mobility, leading to soil ecosystem degradation, groundwater pollution, and severe phytotoxicity to succeeding common bean crops in maize-bean rotation systems. Most previously reported atrazine-degrading strains have only been evaluated in liquid culture, while systematic assessments of their efficacy in soil remediation, soil microecology recovery, and crop safety remain limited, restricting their agricultural application. This study aimed to elucidate the atrazine degradation performance of Paenarthrobacter nitroguajacolicus G1-N1A in soil, reveal its regulatory effects on soil enzyme activities and bacterial communities, and evaluate its capacity to mitigate atrazine-induced oxidative damage in common bean. Soil incubation degradation experiment, high-throughput sequencing, and pot phytotoxicity experiments were conducted. Atrazine residues in soil were quantified by HPLC, degradation metabolites were identified by LC-MS, the activities of soil sucrase, urease and cellulase were measured using biochemical assay kits, and leaf antioxidant enzyme activities, MDA content, and chlorophyll content were determined in common bean seedlings exposed to a 0-50 mg·kg-1 atrazine gradient. The results showed that strain G1-N1A degraded 85.2% of 10 mg·kg-1 atrazine within one day in non‑sterile soil, with cyanuric acid identified as the major degradation product via the trzN, atzB, and atzC gene pathways. Inoculation with G1-N1A significantly alleviated the atrazine-induced inhibition of soil sucrase, urease, and cellulase activities, reshaped the bacterial community composition, increased bacterial richness, and accelerated community succession. Pot experiments confirmed that G1-N1A effectively alleviated atrazine phytotoxicity, promoted seedling biomass accumulation, and reduced the elevated activities of antioxidant enzymes as well as MDA accumulation, while maintaining high leaf chlorophyll content across all pollution gradients. Compared with previously reported atrazine-degrading bacteria, strain G1-N1A demonstrates an ultra-fast soil degradation capacity and multi-functional remediation effects, encompassing pollutant removal, soil ecological restoration, and crop protection. This strain represents an environmentally friendly bioaugmentation agent for the green remediation of atrazine-contaminated farmland. This study provides theoretical support and a technical reference for eliminating herbicide residue hazards and ensuring safe production in maize-legume rotation systems in Northeast China.