Effect Of The Sublethal Doses Of Imidacloprid On The Bacterial Diversity In The Midgut Of Apis Mellifera Ligustica

Honey bees are the most important pollinators in natural ecosystems world-wide, and play an important role in biodiversity maintenance and ecosystem function. They, therefore, have been widely considered as an important insect in the biosafety assessment of insecticides. A number of findings are revealing that that gut bacteria of honeybees play a major role in neutralization of dietary toxins, nutrition, and in defense against pathogens and there is a strict interconnection between the intestinal microbiota balance and the health status of the honeybees. In this study, the potential side effects of the sublethal doses of imidacloprid on the midgut bacteria of the worker bees of Apis mellifera ligustica was investigated under laboratory conditions so as to provide a theoretical basis for the biosafety assessment of pesticides.Newly emerged bees were fed with different sublethal doses of imidacloprid syrups(0.045 mg/L,0.015 mg/Land 0.005 mg/L)and pure sugar syrup with 0.3% acetone, and samples were collected after 3, 6, 9, 12 and 15 d respectively. Every treatment above was sampled 3 times. The population structure of bacterial in the midgut of honeybees in the four treatment groups was analyzed using next-generation sequencing after the genomic DNA was gained from intestinal bacteria. The results are as follows:1. The partial bacterial V3 region of 16 S rRNA gene sequences of PCR products were sequenced bythe Illumina HiSeq 2500. A total of 27 673 383 of V3 16 S rRNA sequences reads from the 60 samples with an average of 461 223 sequences reads for each sample(the minimum of one sample was 356 486 and the maximum was 529 077) were used for this project.2. Following quality filtering, we generated a data set consisting of 15 102 475 high-quality and classifiable 16 S rRNA gene sequences for further analysis. They were classified into different taxonomy using QIIME. The taxon abundance of each sample was generated into phylum, class, order, family, and genera levels using mainly database of RDP, aided by Greengene databases. At the phylum level, Proteobacteria and Firmicutes were the most dominant bacterial phyla, which consistently occurred in bacterial community of honeybees3. In order to explore how the sublethal doses of imidacloprid affect the composition of midgut bacteria, the composition of dominant midgut bacterial genera were analyzed for statistical significance among the four treatments in the same period by performing a T-test, and no significant differences were observed(P>0.05).4. In order to explore how the sublethal doses of imidacloprid affect the structure of midgut bacteria, the richness estimators, including Shannon, chao1, and ACE, were analyzed for statistical significance among the four treatments in the same period by performing a T-test, and no significant differences were observed(P>0.05).The results showed that the sublethal doses of imidacloprid did not induce significant changes of the honeybee gut bacterial community composition under laboratory conditions.