Effects of tefluthrin and guadipyr on the midgut bacteria of adult Apis mellifera

The objective of this study is to assess the potential impact of tefluthrin and guadipyr on the gut microbial composition and metabolism in adult Apis mellifera ligustica, thereby elucidating the underlying mechanisms of insecticide action and its practical implications for bee protection. In this investigation, A. mellifera were subjected to one of three dietary conditions: (1) control sugar water, (2) tefluthrin-infused sugar water, or (3) guadipyr-infused sugar water. After a 10-day exposure period, genomic DNA from the gut bacteria was extracted. High-throughput sequencing was employed to evaluate the potential influence of tefluthrin and guadipyr treatments on the diversity and abundance of gut bacteria. Among the A. mellifera specimens, a total of twenty species of gut bacteria were identified, spanning across five phyla, six classes, eleven orders, eleven families, and fifteen genera. The dominant phyla within the gut bacterial community were Proteobacteria and Bacteroidetes. In comparison to the control group, both the tefluthrin-treated and deltamethrin-treated groups exhibited alterations in the composition of their gut bacterial flora. At the phylum level, there was a significant decrease in the relative abundance of Cyanobacteria (P < 0.05). On the genus level, the tefluthrin group displayed a significant increase in the relative abundance of Bartonella and Serratia (P < 0.05). In the guadipyr-treated group, the relative abundance of Gilliamella and Frischella increased significantly (P < 0.05), while the relative abundance of norank_o_Chloroplast and Enterobacter decreased significantly (P < 0.05). Further analysis of cluster of orthologous genes predicted functional changes in gut microbial metabolism following tefluthrin exposure but no significant changes after guadipyr exposure. Consequently, exposure to tefluthrin and guadipyr can induce shifts in both the composition and metabolic activity of the gut bacteria in A. mellifera. Notably, the impact of tefluthrin on the gut bacteria of A. mellifera appears to be more pronounced compared to that of guadipyr.