Diversity and function of intestinal bacteria in adult Monochamus alternatus Hope (Coleoptera:Cerambycidae) fed indoors and outdoors

Abstract:

[Objective] In order to clarify the bacterial community structure in the midgut and hindgut of adult Monochamus alternatus, and to explore the potential function of intestinal bacteria. [Methods] The gut DNA from 15 individuals (15 midguts, 15 hindguts of outdoor and 15 midguts, 15 hindguts of indoor) of adult Monochamus alternatus fed indoors and outdoors were extracted. The 16S rDNA V3-V4 region of the intestinal bacteria of Monochamus alternatus was sequenced through next generation sequencing techniques. The number of OTUs was counted, the species composition, alpha diversity and beta diversity were analyzed, and the functions of intestinal bacteria were predicted by PICRUSt software. [Results] A total of 544180 high-quality sequences were obtained and clustered into 615 OTUs under 97% similarity, which were annotated into 22 phyla, 48 classes, 112 orders, 172 families, 285 genera and 408 species. The number of OTUs in indoor population was more than that in outdoor population, and there were differences between indoor and outdoor population. The difference between midgut and hindgut of the same population was not obvious. Proteobacteria was the most dominant genus of intestinal bacteria in both indoor and outdoor populations of Monochamus alternatus; Enterobacter was the most dominant genus of intestinal bacteria in outdoor populations and hindgut bacteria in indoor populations, Serratia was the most dominant genus of midgut bacteria in indoor populations. The results of alpha diversity showed that the richness of intestinal bacterial community in indoor populations was significantly higher than that in outdoor populations, and the beta diversity showed that the homogeneity and stability of intestinal bacterial community in outdoor populations were better than that in indoor populations. There was no significant difference in bacterial richness and diversity between the midgut and hindgut of outdoor and indoor populations. The results of functional prediction showed that the metabolic pathway was the most abundant in the intestinal bacteria of adults, which mainly consisted of carbohydrate metabolism and amino acid metabolism, and these bacteria were also able to degrade xenobiotics, terpenoids, polyketides and other secondary metabolites. There was no significant difference in functional abundance among different populations and different intestinal segments. [Conclusion] The community structure and difference of bacteria in the midgut and hindgut of adult Monochamus alternatus fed on different food were determined. The potential role of intestinal bacteria was understood, which provided a theoretical basis for further investigating the function of intestinal symbiosis bacteria of Monochamus alternatus.