松墨天牛成虫室内外种群肠道细菌的多样性及功能分析

【目的】为明确松墨天牛Monochamus alternatus成虫中、后肠细菌群落结构,探索肠道细菌的潜在功能。【方法】分别提取室外和室内饲养的松墨天牛成虫各15头(室内和室外各15个中肠、15个后肠)的肠道DNA,利用二代测序技术对松墨天牛成虫肠道细菌的16S rDNA V3–V4区序列进行测序,统计操作分类单元(OTUs)数量,分析物种组成、Alpha多样性和Beta多样性;采用PICRUSt软件预测肠道细菌的功能。【结果】共获得544180条高质量序列,在97%相似度下将其聚类为615个OTUs,总共注释到22个门、48个纲、112个目、172个科、285个属和408个种。室内种群的OTUs数量多于室外种群,室内外种群的OTUs种类存在差异性。同一种群的中、后肠之间差异不明显。变形菌门Proteobacteria为室内外松墨天牛肠道细菌的最优势门;肠杆菌属Enterobacter为室外种群肠道细菌和室内种群后肠细菌的最优势属,沙雷氏菌属Serratia为室内种群中肠的最优势属。Alpha多样性结果表明松墨天牛成虫室内种群肠道菌群的丰度显著高于室外种群;Beta多样性结果显示室外种群肠道菌群均一性和稳定性比室内种群好。室外和室内种群的中肠与后肠之间在菌群丰度和多样性上均无显著差异。功能预测结果表明,室内外松墨天牛成虫肠道菌群中代谢通路的丰度最高,其中以糖类代谢和氨基酸代谢为主,还有降解外源化学物质、萜类和聚酮类化合物及其他次生代谢物质的能力。不同种群、不同肠段之间的功能丰度均无显著差异。【结论】明确了取食不同食料的松墨天牛成虫中、后肠的细菌群落结构及差异,了解了肠道细菌的潜在作用,为进一步探究松墨天牛肠道共生菌的功能提供了理论基础。

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

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.