Symbiotic Escherichia coli promotes the developmental timing of Drosophila melanogaster

Abstract:

[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.