Effects Of Glyphosate Exposure On Symbiotic Bacteria In The Harmonia Axyridis(Coleoptera:Coccinellidae)

The herbicide glyphosate is expected to be innocuous to animals for a long time,because it targets an enzyme only found in plants and microorganisms.However,recent studies have shown that glyphosate had a negative impact on insect survival.In particular,glyphosate can affect the growth and development of host insects by perturbing microbial community composition and diversity.The commercialization of genetically modified crops has promoted the increase continuously in volume of herbicide glyphosate use,which accounts for half of the global herbicide market.Predatory natural enemiesas,Harmonia axyridis as research subject,a focus on insect symbiotic bacteria in order to clarify the safety of glyphosate to non-target organisms in the field.The research demonstrated systematically effects of microbial community composition and structure following glyphosate exposure of H.axyridis larvae and adults through using high-throughput sequencing and techniques of molecular biology.The main results are as follows: 1.Diversity and community composition of symbiotic bacteria of different developmental stages of H.axyridisFirst of all,they were measured and analyzed during different developmental stages of H.axyridis by using high-throughput sequencing in order to determine the composition and structure of the symbiotic community of H.axyridis.Results showed that bacterial community in the H.axyridis at all developmental stages were annotated into 22 phyla,43 classes,82 orders,142 families,204 genera.The richness and diversity of bacteria at different developmental stages were different,and the bacteria in the 2nd-instar larvae were of low diversity,and the bacteria in the egg and adults were higher diversity.The dominant bacteria at phyla level were Firmicutes,Proteobacteria and Actinobacteria.The dominant bacteria at genus level were mainly Staphylococcus,Enterobacter,Glutamicibacter,Acinetobacter,and Corynebacterium＿1.The results clarified the diversity and composition of the bacterial community of the H.axyridis,and laid a foundation for further studying the effect of the symbiotic bacteria of the H.axyridis after glyphosate exposure.2.Effects of bacterial community of the H.axyridis larva after glyphosate exposure.Based on 16 S r DNA sequencing,we analyzed the diversity and composition of symbiotic bacteria of the H.axyridis larva after glyphosate exposure.There was no significant difference in diversity and richness of symbiotic bacteria of the H.axyridis larva after glyphosate exposure compared to control.The dominant bacteria under the glyphosate exposure treatments belong to the same phylums like Firmicutes and Proteobacteria.Similarly,they were from the same genus like Staphylococcus,Enterobacter,Acinetobacter and Enterococcus.However,the abundance of their dominant bacteria was different.5 mg/L glyphosate(G5),10 mg/L glyphosate(G10)promoted the reduction of abundance of Staphylococcus and the increase of abundance of Enterobacter.but 20 mg/L glyphosate(G20)had no significant effect on the abundance of the dominant genus.From the perspective of growth and development indicators,the survival of H.axyridis larva was no significantly reduced under the concentration of 20 mg/L glyphosate(P >0.05),but glyphosate can significantly affected body mass of H.axyridis.3.Effects of bacterial community of the H.axyridis adults after glyphosate exposure.Harmonia axyridis adult as research subject,the results showed that there was no significant difference in the reproduction of H.axyridis after glyphosate exposure.Based on 16 S r DNA sequencing,There was no significant difference in composition and structure of symbiotic bacteria of the H.axyridis adults after glyphosate exposure compared to control.The dominant bacteria at phyla level were Proteobacteria and Firmicutes.The dominant bacteria at genus level were mainly Serratia,Lactococcus,Enterobacter,Staphylococcus,and Hafnia-Obesumbacterium.Meanwhile,the results also demonstrated that there was no significant effect on the abundance of dominant bacteria of the H.axyridis adults after glyphosate exposure compared to control.