Data from: The route of infection determines Wolbachia antibacterial protection in Drosophila

Bacterial symbionts are widespread among metazoans and provide a range of beneficial functions. Wolbachia-mediated protection against viral infection has been extensively demonstrated in Drosophila. In mosquitoes that are artificially transinfected with Drosophila melanogaster Wolbachia (wMel), protection from both viral and bacterial infections has been demonstrated. However, no evidence for Wolbachia-mediated antibacterial protection has been demonstrated in Drosophila to date. Here, we show that the route of infection is key for Wolbachia-mediated antibacterial protection. Drosophila melanogaster carrying Wolbachia showed reduced mortality during enteric—but not systemic—infection with the opportunist pathogen Pseudomonas aeruginosa. Wolbachia-mediated protection was more pronounced in male flies and is associated with increased early expression of the antimicrobial peptide Attacin A, and also increased expression of a reactive oxygen species detoxification gene (Gst D8). These results highlight that the route of infection is important for symbiont-mediated protection from infection, that Wolbachia can protect hosts by eliciting a combination of resistance and disease tolerance mechanisms, and that these effects are sexually dimorphic. We discuss the importance of using ecologically relevant routes of infection to gain a better understanding of symbiont-mediated protection.

细菌共生体（bacterial symbionts）广泛分布于后生动物（metazoans）体内，并可为宿主提供多样有益功能。沃尔巴克氏体（Wolbachia）介导的抗病毒感染保护效应已在果蝇（Drosophila）中得到广泛验证。在人工转感染黑腹果蝇（Drosophila melanogaster）沃尔巴克氏体wMel株的蚊虫中，其对病毒与细菌感染的保护作用均已被证实。然而截至目前，尚未有研究在果蝇中发现沃尔巴克氏体介导的抗菌保护相关证据。本研究证实，感染途径是决定沃尔巴克氏体能否介导抗菌保护作用的关键因素。携带沃尔巴克氏体的黑腹果蝇，在经肠道而非全身性途径感染机会致病菌铜绿假单胞菌（Pseudomonas aeruginosa）后，死亡率显著降低。该沃尔巴克氏体介导的保护作用在雄性果蝇中更为显著，且与抗菌肽Attacin A的早期表达上调，以及活性氧（reactive oxygen species）解毒基因Gst D8的表达升高密切相关。上述结果凸显了三点核心结论：其一，感染途径对共生体介导的抗感染保护作用至关重要；其二，沃尔巴克氏体可通过激活抗性与疾病耐受的协同机制实现宿主保护；其三，此类保护效应存在性别二态性。本文还探讨了采用生态相关的感染途径，以更深入地解析共生体介导的宿主保护作用的重要意义。