Combination of degrading with non-degrading endophytic bacteria synergistically enhances rice resistance to chlorpyrifos stress

INTRODUCTION: The continuous application of pesticides leads to persistent environmental residues that adversely affect non-target plants. However, the effect of pesticides on the endophytic microbial communities of plants and the feedback of enriched endophytes in alleviating pesticide-induced stress remain poorly understood. OBJECTIVES: This study aims to elucidate the roles and mechanisms by which endophytic bacteria collectively modulate rice plant resilience to chlorpyrifos (CP) stress. METHODS: We systematically compared the responses of axenic and holoxenic rice to six different pesticides. Using CP as a model, we analyzed the bacterial communities enriched in rice plants under CP stress and characterized the functional traits. Based on functional profiles, we then constructed synthetic consortia to investigate how interactions among bacterial functions drive the degradation pathway of CP in rice. RESULTS: Application of six different pesticides induced oxidative stress in rice, whereas endophytic bacteria alleviated growth inhibition. In response to CP stress, rice plants enriched endophytic bacteria from the phylum Proteobacteria, particularly Pseudomonas and Hydrogenophaga. We isolated 66 endobacterial strains, including 15 capable of CP degradation and 42 strains with growth-promoting properties. Functional combination experiments using Pseudomonas revealed that when degradation activity was present, increasing functional richness in synthetic microbial consortia further enhanced CP degradation in rice. Notably, the combination of CP-degrading strain p4 with non-degrading strain p6 exhibited a metabolic synergistic effect. Strain p4 transformed CP into eight metabolites via hydrolysis, oxidation, and alkylation, which were subsequently converted into less toxic conjugates through plant Phase II metabolism, a process promoted by strain p6. CONCLUSION: Our work demonstrates that the synergistic interaction between degrading and non-degrading endophytic bacteria enhances rice plant resistance to CP stress. These findings deepen our understanding of microbial mechanisms involved in plant responses to organic pollutants stress and provide insights for designing synthetic microbial consortia.