[Background] The symbiotic microbiota profoundly affects many aspects of host physiology,but the diversity and complexity of microbial community make it difficult to explore the underlying mechanism in vertebrates.Fruit fly Drosophila provides us a germ-free and gnotobiotic model to investigate the interaction of microbes and hosts.[Objective] To isolate and identify Escherichia coli from Drosophila melanogaster gut and investigate the effects of E.coli on the development of hosts.[Methods] E.coli was isolated with selective medium and identified with BLASTn analysis of 16S rRNA gene.In vitro and in vivo co-existence test were used to verify the symbiosis.Through the developmental timing and growth rate experiments,the effect of E.coli on hosts' development were investigated.Real-time quantitative PCR were used to assess gene expression levels of PTTH and insulin signaling pathways.[Results] We isolated and identified indigenous strains of E.coli in the guts of both lab-reared and wild-captured Drosophila.E.coli was co-cultured with commensal Lactobacillus plantarum in vitro,and in vivo colonized the fly gut,indicating that E.coli was one symbiotic member of the bacterial community of Drosophila.Moreover,E.coli facilitated the development of Drosophila by accelerating the growth rate.At the molecular level,E.coli significantly stimulated the activity of PTTH and insulin signaling that is essential for the larval/pupal transmission in Drosophila.[Conclusion] E.coli was symbiotic bacteria of Drosophila and promoted the development of Drosophila.%[背景]共生菌对宿主的很多生理功能有着重要影响,但微生物菌群的多样性和复杂性使得探索其潜在的机制存在困难.黑腹果蝇的无菌和悉菌模型可以被用来研究细菌和宿主的相互作用.[目的]分离和鉴定果蝇肠道大肠杆菌,并研究其对宿主生长发育的影响.[方法]利用大肠杆菌选择性培养基分离果蝇肠道大肠杆菌,通过16S rRNA基因序列比对鉴定菌株.利用体外和体内定殖实验验证共生关系.通过果蝇的发育历期和生长速率实验检测该细菌对宿主生长发育的影响.利用RT-qPCR技术对促胸腺激素及胰岛素信号通路相关基因的表达水平进行检测.[结果]从实验室饲养和野生果蝇肠道体内分离并鉴定得到大肠杆菌.体内和体外定殖试验中大肠杆菌可以和果蝇肠道共生菌共存,说明大肠杆菌是果蝇肠道共生菌.另外,大肠杆菌通过提高果蝇生长速率促进其发育.在分子水平上,大肠杆菌可以激活果蝇体内脑促胸腺激素和胰岛素信号通路相关基因的表达.[结论]大肠杆菌是果蝇肠道共生菌并能促进果蝇生长发育.
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