House flies (Musca domestica) are widespread, synanthropic filth flies commonly found on decaying matter, garbage, and feces as well as human food. They have been shown to vector microbes, including clinically relevant pathogens. Previous studies have demonstrated that house flies carry a complex and variable prokaryotic microbiota, but the main drivers underlying this variability and the influence of habitat on the microbiota remain understudied. Moreover, the differences between the external and internal microbiota and the eukaryotic components have not been examined. To obtain a comprehensive view of the fly microbiota and its environmental drivers, we sampled over 400 flies from two geographically distinct countries (Belgium and Rwanda) and three different environments-farms, homes, and hospitals. Both the internal as well as external microbiota of the house flies were studied, using amplicon sequencing targeting both bacteria and fungi. Results show that the house fly's internal bacterial community is very diverse yet relatively consistent across geographic location and habitat, dominated by genera Staphylococcus and Weissella. The external bacterial community, however, varies with geographic location and habitat. The fly fungal microbiota carries a distinct signature correlating with the country of sampling, with order Capnodiales and genus Wallemia dominating Belgian flies and genus Cladosporium dominating Rwandan fly samples. Together, our results reveal an intricate country-specific pattern for fungal communities, a relatively stable internal bacterial microbiota and a variable external bacterial microbiota that depends on geographical location and habitat. These findings suggest that vectoring of a wide spectrum of environmental microbes occurs principally through the external fly body surface, while the internal microbiome is likely more limited by fly physiology.

中文翻译：

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家蝇的家蝇的微生物群落随地理位置和栖息地的不同而不同。

家蝇（Musca domestica）是广泛存在的，会腐烂的蝇类蝇，通常见于腐烂的物质，垃圾，粪便以及人类食物。它们已被证明可引导微生物，包括与临床相关的病原体。先前的研究表明，家蝇携带着复杂而易变的原核生物群，但是导致这种变异性以及栖息地对微生物群的影响的主要驱动力仍未得到充分研究。此外，尚未检查内部和外部微生物群与真核生物成分之间的差异。为了全面了解果蝇微生物群及其环境驱动因素，我们对来自两个地理上不同的国家（比利时和卢旺达）和三个不同环境的农场，家庭和医院的400多个果蝇进行了采样。使用针对细菌和真菌的扩增子测序研究了家蝇的内部和外部微生物群。结果显示，家蝇的内部细菌群落非常多样，但在地理位置和栖息地上相对一致，主要由葡萄球菌和魏氏菌属组成。但是，外部细菌群落随地理位置和栖息地的不同而不同。苍蝇真菌的菌群带有明显的特征，与采样国有关，Cap藜科和Wallemia属占比利时苍蝇的主要部分，而克拉多孢菌属则占卢旺达苍蝇的样品的主要部分。在一起，我们的结果揭示了针对真菌群落的错综复杂的国家/地区模式，相对稳定的内部细菌菌群和可变的外部细菌菌群，具体取决于地理位置和栖息地。这些发现表明，广泛传播环境微生物的方法主要是通过蝇体外表面进行的，而内部微生物组可能更受蝇生理的限制。