A dynamic partnership: exploring the function and control of extracellular symbionts in thyasirid bivalves

动态伙伴关系：探索胸腺双壳类细胞外共生体的功能和控制

• 批准号: RGPIN-2020-04131
• 负责人: Dufour, Suzanne
• 金额: $ 3.3万
• 依托单位: Memorial University of Newfoundland
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=716569
• 关键词: dynamic; partnership; exploring; function; control

Throughout their lives, animals constantly interact with bacteria. While some of these bacteria are disease-causing pathogens, many others are harmless or even beneficial. Some bacteria are even fundamentally important for the nutrition, development of immunity of the animals with which they interact; for example, many of the bacteria that dwell in our digestive tracts are crucial to our health and well-being. Despite increasing research interest in recent years, we know very little about the complex interactions that take place between animals and beneficial bacteria. For example, how do such dramatically different organisms find each other, form associations, and maintain good relationships over the long term? My research program seeks to understand how animals and beneficial bacteria interact, cooperate and exchange resources. To do so, I study small, cold-water clams called thyasirids that burrow in sulfur-containing sediments in many harbours, fjords, and offshore locations around Canada. Thyasirids are considered as ecosystem engineers because their burrowing activities help remove sulfur (which is toxic to most animals) from sediments. The gills of thyasirids harbour large populations of bacteria (“symbionts”) that use sulfur as an energy source. Thyasirids provide their symbionts with the sulfur they need by burrowing in sediments using their extensible foot, a behaviour called sulfur mining; in turn, symbionts are a supplementary food source for the clams. Thyasirid sulfur mining changes the chemistry of sediments around burrows and may enhance the colonization of certain bacteria around burrow linings. My students and I will keep symbiotic thyasirids in aquaria while manipulating environmental conditions and monitoring their behaviour. We will also perform detailed observations of host tissues (for example, using specialized microscopes to visualize and quantify bacteria, or fluorescent markers to track cellular processes such as cell division or cell death), to understand the factors that are important for maintaining a functioning symbiosis in thyasirids. Further, we will use genome sequencing approaches to gain insights on potential symbiont genes involved in host interactions, and study the free-living form of thyasirid symbionts to see if they are attracted to the burrow linings of their host clams. This research is important for understanding how all animals interact with beneficial bacteria; in particular, it is expected to provide novel insights on the importance of host behaviours for maintaining and fine-tuning symbiotic relationships. Further, this work will help us better characterize the ecological role of thyasirids in Canadian waters; such knowledge is timely given that sediments in our coastal waters are experiencing an increasing degree of sulfur enrichment as a result of organic matter loading, and symbiotic thyasirids could readily colonize and transform these impacted sediments.

在它们的一生中，动物不断地与细菌相互作用。虽然其中一些细菌是致病的病原体，但许多其他细菌是无害的，甚至是有益的。有些细菌甚至对与它们相互作用的动物的营养和免疫力的发展至关重要;例如，居住在我们消化道中的许多细菌对我们的健康和福祉至关重要。尽管近年来研究兴趣越来越大，但我们对动物和有益细菌之间发生的复杂相互作用知之甚少。例如，如此截然不同的生物体是如何找到彼此、形成联系并长期保持良好关系的？我的研究项目旨在了解动物和有益细菌如何相互作用，合作和交换资源。为了做到这一点，我研究了小型冷水蛤蜊，称为thyasirids，在加拿大周围的许多港口，峡湾和近海地区的含硫沉积物中挖掘。Thyasirids被认为是生态系统工程师，因为它们的穴居活动有助于从沉积物中去除硫（对大多数动物有毒）。囊鲶类的鳃里有大量的细菌（共生体），它们利用硫作为能量来源。Thyasirids通过使用其可伸展的脚在沉积物中挖掘，为它们的共生体提供所需的硫，这种行为称为硫采矿;反过来，共生体是蛤蜊的补充食物来源。Thyasirid硫磺开采改变了洞穴周围沉积物的化学性质，并可能增强洞穴衬里周围某些细菌的定植。我和我的学生将在水族馆中饲养共生的甲状腺虫，同时控制环境条件并监测它们的行为。我们还将对宿主组织进行详细的观察（例如，使用专用显微镜来观察和量化细菌，或使用荧光标记物来跟踪细胞过程，如细胞分裂或细胞死亡），以了解对维持甲状腺功能共生的重要因素。此外，我们将使用基因组测序方法来深入了解参与宿主相互作用的潜在共生体基因，并研究thyasirid共生体的自由生活形式，看看它们是否被吸引到宿主蛤的洞穴衬里。这项研究对于了解所有动物如何与有益细菌相互作用非常重要;特别是，它有望为宿主行为对维持和微调共生关系的重要性提供新的见解。此外，这项工作将有助于我们更好地描述在加拿大沃茨的thyasirids的生态作用，这样的知识是及时的，在我们的沿海沃茨的沉积物正在经历一个越来越大的程度的硫富集的结果，有机物负载，共生thyasirids可以很容易地殖民和改造这些受影响的沉积物。