Sanaei Ehsan, Charlat Sylvain, Engelstädter Jan
School of Biological Sciences, The University of Queensland, Saint Lucia, Brisbane, QLD, 4067, Australia.
Laboratoire de Biométrie et Biologie Evolutive, Université de Lyon, Université Lyon 1, CNRS, UMR 5558, 43 boulevard du 11 novembre 1918, Villeurbanne, F-69622, France.
Biol Rev Camb Philos Soc. 2021 Apr;96(2):433-453. doi: 10.1111/brv.12663. Epub 2020 Oct 30.
Wolbachia is one of the most abundant endosymbionts on earth, with a wide distribution especially in arthropods. Effective maternal transmission and the induction of various phenotypes in their hosts are two key features of this bacterium. Here, we review our current understanding of another central aspect of Wolbachia's success: their ability to switch from one host species to another. We build on the proposal that Wolbachia host shifts occur in four main steps: (i) physical transfer to a new species; (ii) proliferation within that host; (iii) successful maternal transmission; and (iv) spread within the host species. Host shift can fail at each of these steps, and the likelihood of ultimate success is influenced by many factors. Some stem from traits of Wolbachia (different strains have different abilities for host switching), others on host features such as genetic resemblance (e.g. host shifting is likely to be easier between closely related species), ecological connections (the donor and recipient host need to interact), or the resident microbiota. Host shifts have enabled Wolbachia to reach its enormous current incidence and global distribution among arthropods in an epidemiological process shaped by loss and acquisition events across host species. The ability of Wolbachia to transfer between species also forms the basis of ongoing endeavours to control pests and disease vectors, following artificial introduction into uninfected hosts such as mosquitoes. Throughout, we emphasise the many knowledge gaps in our understanding of Wolbachia host shifts, and question the effectiveness of current methodology to detect these events. We conclude by discussing an apparent paradox: how can Wolbachia maintain its ability to undergo host shifts given that its biology seems dominated by vertical transmission?
沃尔巴克氏体是地球上数量最为丰富的内共生菌之一，分布广泛，尤其在节肢动物中。有效的母系传播以及在宿主中诱导各种表型是这种细菌的两个关键特征。在此，我们回顾一下目前对沃尔巴克氏体成功的另一个核心方面的理解：它们从一个宿主物种转移到另一个宿主物种的能力。我们基于这样一种观点展开论述，即沃尔巴克氏体宿主转移主要通过四个步骤发生：（i）物理转移到一个新物种；（ii）在该宿主内增殖；（iii）成功的母系传播；以及（iv）在宿主物种内传播。宿主转移可能在这些步骤中的每一步都失败，最终成功的可能性受到许多因素的影响。有些因素源于沃尔巴克氏体的特性（不同菌株的宿主转换能力不同），其他因素则与宿主特征有关，如遗传相似性（例如，在亲缘关系较近的物种之间宿主转移可能更容易）、生态联系（供体宿主和受体宿主需要相互作用）或常驻微生物群。宿主转移使沃尔巴克氏体在一个由跨宿主物种的丧失和获得事件所塑造的流行病学过程中，达到了目前在节肢动物中极高的发生率和全球分布。沃尔巴克氏体在物种间转移的能力也构成了目前通过人工将其引入未感染宿主（如蚊子）来控制害虫和病媒的努力的基础。在整个论述过程中，我们强调了在理解沃尔巴克氏体宿主转移方面存在的许多知识空白，并对当前检测这些事件的方法的有效性提出质疑。我们通过讨论一个明显的悖论来得出结论：鉴于沃尔巴克氏体的生物学特性似乎以垂直传播为主，它如何能够保持进行宿主转移的能力？
