Bouchon Didier, Zimmer Martin, Dittmer Jessica
UMR CNRS 7267, Ecologie et Biologie des Interactions, Université de Poitiers Poitiers, France.
Leibniz Center for Tropical Marine Ecology Bremen, Germany.
Front Microbiol. 2016 Sep 23;7:1472. doi: 10.3389/fmicb.2016.01472. eCollection 2016.
Bacterial symbionts represent essential drivers of arthropod ecology and evolution, influencing host traits such as nutrition, reproduction, immunity, and speciation. However, the majority of work on arthropod microbiota has been conducted in insects and more studies in non-model species across different ecological niches will be needed to complete our understanding of host-microbiota interactions. In this review, we present terrestrial isopod crustaceans as an emerging model organism to investigate symbiotic associations with potential relevance to ecosystem functioning. Terrestrial isopods comprise a group of crustaceans that have evolved a terrestrial lifestyle and represent keystone species in terrestrial ecosystems, contributing to the decomposition of organic matter and regulating the microbial food web. Since their nutrition is based on plant detritus, it has long been suspected that bacterial symbionts located in the digestive tissues might play an important role in host nutrition via the provisioning of digestive enzymes, thereby enabling the utilization of recalcitrant food compounds (e.g., cellulose or lignins). If this were the case, then (i) the acquisition of these bacteria might have been an important evolutionary prerequisite for the colonization of land by isopods, and (ii) these bacterial symbionts would directly mediate the role of their hosts in ecosystem functioning. Several bacterial symbionts have indeed been discovered in the midgut caeca of terrestrial isopods and some of them might be specific to this group of animals (i.e., Hepatoplasma crinochetorum, Hepatincola porcellionum, and ), while others are well-known intracellular pathogens ( spp.) or reproductive parasites ( sp.). Moreover, a recent investigation of the microbiota in has revealed that this species harbors a highly diverse bacterial community which varies between host populations, suggesting an important share of environmental microbes in the host-associated microbiota. In this review, we synthesize our current knowledge on the terrestrial isopod microbiome and identify future directions to (i) fully understand the functional roles of particular bacteria (both intracellular or intestinal symbionts and environmental gut passengers), and (ii) whether and how the host-associated microbiota could influence the performance of terrestrial isopods as keystone species in soil ecosystems.
细菌共生体是节肢动物生态和进化的重要驱动因素，影响着宿主的营养、繁殖、免疫和物种形成等特征。然而，关于节肢动物微生物群的大多数研究都是在昆虫中进行的，需要对不同生态位的非模式物种开展更多研究，以完善我们对宿主与微生物群相互作用的理解。在本综述中，我们将陆生等足类甲壳动物作为一种新兴的模式生物，用于研究与生态系统功能潜在相关的共生关系。陆生等足类动物是一群已经进化出陆地生活方式的甲壳动物，是陆地生态系统中的关键物种，有助于有机物的分解并调节微生物食物网。由于它们的营养基于植物碎屑，长期以来人们一直怀疑位于消化组织中的细菌共生体可能通过提供消化酶在宿主营养中发挥重要作用，从而使宿主能够利用难降解的食物化合物（如纤维素或木质素）。如果是这样，那么（i）获取这些细菌可能是等足类动物在陆地上定殖的重要进化前提，并且（ii）这些细菌共生体将直接介导其宿主在生态系统功能中的作用。确实，在陆生等足类动物的中肠盲囊中发现了几种细菌共生体，其中一些可能是该类动物特有的（即，克氏肝浆菌、鼠妇肝杆菌，以及），而其他一些是著名的细胞内病原体（属）或生殖寄生虫（种）。此外，最近对的微生物群调查显示，该物种拥有高度多样化的细菌群落，且在不同宿主种群之间存在差异，这表明环境微生物在宿主相关微生物群中占重要比例。在本综述中，我们综合了目前关于陆生等足类动物微生物组的知识，并确定了未来的研究方向，以（i）全面了解特定细菌（细胞内或肠道共生体以及环境肠道过客）的功能作用，以及（ii）宿主相关微生物群是否以及如何影响陆生等足类动物作为土壤生态系统关键物种的表现。
