Metabolic and Gut Microbiome Responses to Paraquat Exposure in Apis mellifera Under Laboratory Conditions

Paraquat is a widely used herbicide known to adversely affect honeybee physiology; however, its impact on gut-associated biological processes remains poorly understood. Therefore, intricate effects of paraquat on honeybees highlight the need for a comprehensive understanding of its specific biological consequences. This study aimed to evaluate the gut microbiome composition and metabolomic profiles of honeybees following oral exposure to sublethal (LD25) and toxic (LD50) doses of paraquat, assessed 48 h post-exposure to represent acute exposure. Survival rate and sucrose consumption were monitored to assess toxicity. Honeybee gut samples were analyzed using 16S rRNA gene amplicon sequencing and metabolomic approaches. Both paraquat treatments resulted in increased mortality (p < 0.0001) and reduced sucrose consumption (p = 0.00503). In contrast, gut bacterial community composition remained largely unchanged (p > 0.05). Metabolomic analysis revealed dose-dependent alterations, particularly in metabolites associated with carbohydrate and energy metabolism, including oxaloacetic acid and pyruvic acid. This study provides the first integration of 16S rRNA gene amplicon sequencing and metabolomic analyses to evaluate the effects of paraquat exposure in honeybees. The findings indicate that paraquat-induced stress primarily exhibits as host metabolic reprogramming rather than changes in microbiome composition. These results provide insights into the mechanisms underlying honeybee responses to herbicide stress and may contribute to the development of strategies for honeybee protection.