Instituto Gulbenkian de Ciência, Oeiras, Portugal.
Faculdade de Medicina da Universidade de Lisboa, Lisboa, Portugal.
PLoS Biol. 2018 Jul 5;16(7):e2005710. doi: 10.1371/journal.pbio.2005710. eCollection 2018 Jul.
Animals live together with diverse bacteria that can impact their biology. In Drosophila melanogaster, gut-associated bacterial communities are relatively simple in composition but also have a strong impact on host development and physiology. It is generally assumed that gut bacteria in D. melanogaster are transient and their constant ingestion with food is required to maintain their presence in the gut. Here, we identify bacterial species from wild-caught D. melanogaster that stably associate with the host independently of continuous inoculation. Moreover, we show that specific Acetobacter wild isolates can proliferate in the gut. We further demonstrate that the interaction between D. melanogaster and the wild isolated Acetobacter thailandicus is mutually beneficial and that the stability of the gut association is key to this mutualism. The stable population in the gut of D. melanogaster allows continuous bacterial spreading into the environment, which is advantageous to the bacterium itself. The bacterial dissemination is in turn advantageous to the host because the next generation of flies develops in the presence of this particularly beneficial bacterium. A. thailandicus leads to a faster host development and higher fertility of emerging adults when compared to other bacteria isolated from wild-caught flies. Furthermore, A. thailandicus is sufficient and advantageous when D. melanogaster develops in axenic or freshly collected figs, respectively. This isolate of A. thailandicus colonizes several genotypes of D. melanogaster but not the closely related D. simulans, indicating that the stable association is host specific. This work establishes a new conceptual model to understand D. melanogaster-gut microbiota interactions in an ecological context; stable interactions can be mutualistic through microbial farming, a common strategy in insects. Moreover, these results develop the use of D. melanogaster as a model to study gut microbiota proliferation and colonization.
动物与多种多样的细菌共生，这些细菌会影响它们的生物学特性。在黑腹果蝇中，肠道相关细菌群落的组成相对简单，但对宿主的发育和生理也有很强的影响。一般认为，黑腹果蝇肠道中的细菌是短暂存在的，需要不断摄入食物才能维持其在肠道中的存在。在这里，我们鉴定出一些来自野生黑腹果蝇的细菌物种，这些细菌可以与宿主稳定关联，而不依赖于持续接种。此外，我们还表明，特定的野生醋酸菌可以在肠道中增殖。我们进一步证明，黑腹果蝇与野生分离的醋酸杆菌之间的相互作用是互利的，而肠道关联的稳定性是这种互利共生的关键。黑腹果蝇肠道中的稳定种群允许细菌持续向环境中扩散，这对细菌本身是有利的。细菌的传播反过来又对宿主有利，因为下一代果蝇在存在这种特别有益的细菌的情况下发育。与从野生果蝇中分离出的其他细菌相比，醋酸杆菌泰国亚种会导致宿主发育更快，成虫的繁殖力更高。此外，当黑腹果蝇在无菌或新鲜采集的无花果中发育时，醋酸杆菌泰国亚种是充足且有利的。这种醋酸杆菌泰国亚种可以定植于几个黑腹果蝇的基因型中，但不能定植于亲缘关系密切的黑腹果蝇 simulans 中，这表明稳定的关联是宿主特异性的。这项工作建立了一个新的概念模型，以在生态背景下理解黑腹果蝇-肠道微生物群的相互作用；稳定的相互作用可以通过微生物养殖（昆虫中常见的一种策略）成为互利共生关系。此外，这些结果发展了利用黑腹果蝇作为模型来研究肠道微生物群的增殖和定植。
