Single and Synergistic Effects of Microplastics and Difenoconazole on Oxidative Stress, Transcriptome, and Microbiome Traits in Honey Bees

Microplastics (MPs) and pesticides are identified as two environmental pollutants. In the present study, we showed evidence of toxic effects on honey bees from chronic oral exposure to food containing difenoconazole alone (Dif) and in a binary mixture with polystyrene (PS)-MPs (Dif + PS). We observed a disrupted gut microbial community structure in bees after difenoconazole exposure, and the gut microbiota structure richness increased at the phylum and genus levels in Dif + PS group. Transcriptomic analysis revealed that difenoconazole exposure caused 98 differentially expressed genes (DEGs), while 41 DEGs were identified in Dif + PS group. PS-MPs seemed to mitigate oxidative damage and changes in the transcriptome profile in honey bees caused by difenoconazole to some extent. However, coexposure increased the disordered microbial community composition. Our study highlights the importance of investigating possible additive and synergic activities between stressors to comprehensively understand the effects of pollutants on pollinating insects.