霍氏肠杆菌对黑腹果蝇生长和发育的影响

Enterobacter hormaechei promotes the growth and development of Drosophila melanogaster

摘要:

【背景】共生菌群可以影响宿主的生理、代谢以及神经行为，黑腹果蝇是研究宿主与共生菌作用机制的优秀遗传模型。【目的】分离和鉴定黑腹果蝇体内的共生菌，并研究其对果蝇生长和发育的影响。【方法】利用YG固体培养基分离果蝇肠道菌；革兰氏染色、生化鉴定和16S rRNA基因比对鉴定菌种；体内定殖和世代传递实验验证细菌与果蝇的共生关系；建立无菌和悉菌模型，通过发育历期和生长速率来验证其促生长作用；RT-PCR检测促生长分子基因表达；免疫荧光染色检测果蝇肠道细胞的增殖；葡萄糖氧化酶法检测葡萄糖浓度。【结果】分离到一株能够明显促进果蝇生长发育的细菌，经鉴定为霍氏肠杆菌(Enterobacter hormaechei)，该菌可以稳定定殖于黑腹果蝇肠道以及培养基内，而且可以世代垂直传递。该菌可明显地促进果蝇的生长，并通过加速促胸腺激素的分泌来发挥促生长作用，同时可以促进果蝇肠道细胞的增殖。霍氏肠杆菌相较于无菌果蝇可以降低体内葡萄糖水平。【结论】霍氏肠杆菌是黑腹果蝇的有益共生菌，实验证实其可以促进果蝇的生长和发育。

Abstract:

[Background] Commensal bacteria can affect host’s physiology, metabolism and neural behavior. Drosophila melanogaster is an excellent genetic model to investigate the mechanism of interaction between host and commensal bacteria. [Objective] To isolate and identify the commensal bacteria from D. melanogaster, and investigate their effects on the growth and development of D. melanogaster. [Methods] The YG agar medium was prepared to isolate bacteria from the intestinal tract of D. melanogaster. Gram-staining, biochemical identification and 16S rRNA gene blast were used to identify the bacteria strain. The commensalism between the bacteria and D. melanogaster was verified by colonization and generation transfer experiments. The sterile and gnotobiotic animal models were established to verify the growth promotion effect of E. hormaechei through the development timing and growth rate. RT-PCR was used to examine the molecular markers; immunofluorescence staining monitored proliferation of intestinal cells in fruit flies. [Results] A bacterial strain that could robustly promote the growth of the flies was isolated from the gut of D. melanogaster and identified as E. hormaechei. It stably colonized the gut of D. melanogaster and medium, and could be delivered to descendant. E. hormaechei promoted the growth of the flies obviously via increasing PTTH secretion and promoting the proliferation of intestinal cells in fruit flies. E. hormaechei decreased the level of glucose compared to germ-free flies. [Conclusion] E. hormaechei is a beneficial commensal bacterium of D. melanogaster to promote the growth and development of D. melanogaster.