共生菌在深海贻贝适应重金属环境中的作用和机制研究

Deep-sea mussels of the genus Bathymodiolus are one of the dominant macroorganisms in deep-sea ecosystems including hydrothermal vents and cold seeps. The Bathymodiolus mussels succeed reaching high biomasses in these harsh conditions thanks to chemosynthetic, carbon-fixing bacterial symbionts located in their gill tissue. Characterized by high levels of heavy metals in the vent fluids, hydrothermal fields are regarded as natural platforms to study the environmental adaption and evolution of the bivalves. However, due to the difficulties in sampling and cultivation of the deep-sea mussels, research on metal adaption of the Bathymodiolus mussels remains limited, and the roles of their symbiotic bacteria are unclear. In the present study, by combining deep-sea environmental detection and sampling, and in-door experiments, we will use the deep-sea mussel Bathymodiolus platifrons, widely distributed in the chemosynthetic ecosystems of the Western Pacific, as a toxicological model to investigate the response of deep-sea macroorganism to heavy metal toxicity and explain their adaption strategies under extreme environment. Firstly, we aim to conduct in-door experiments to systematically characterize the effects of heavy metals on the physiological, cellular and molecular levels of the symbiont-containing and symbiont-free mussels, then causal genes and pathways responsible for heavy metal resistance and stress responses will be identified through gene expression profiles. In addition, by deep-sea environmental detection and sampling, we will explain the relationship between symbiotic bacteria content and the metal levels from different sampling locations (vents and seeps), by analysis of metal accumulation, antioxidant enzyme activity, cellular structural changes, and expression of the selected genes of Bathymodiolus mussels from different locations, we will figure out the effects of the content of symbiotic bacteria on the Bathymodiolus mussels under metal exposure from physiological, cellular and molecular aspects, the roles of symbiotic bacteria will then be evaluated. This work will further reveal underlying adaption mechanisms of deep-sea mussels to metal envrionment from symbiotic aspect, enrich our knowledge of the special life process in the deep sea, and also provide model theoretical basis for the study of deep-sea endosymbiosis.

深海贻贝是深海热液和冷泉中的优势生物，共生是其适应深海独特环境的关键。深海热液区高重金属环境为研究双壳类环境适应机制提供有利的平台。由于深海样品的难获取和培养，国内外对深海贻贝重金属适应机制的研究不深入且未突出共生菌的作用。本研究以西太平洋化能生态系统中的优势种 — 平端深海偏顶蛤为研究对象，基于前期建立的深海贻贝活体取样和长期培养体系，结合室内实验和野外调查开展深海贻贝重金属适应机制的研究。室内实验基于构建的携带和非携带共生菌的深海贻贝群体，从生理、细胞、分子水平比较二者在重金属胁迫下响应规律，利用转录组测序，筛选与重金属胁迫相关的关键基因和通路；野外调查探索深海贻贝体内共生菌含量与环境重金属浓度的关系，探讨不同含量的共生菌在生理、细胞和分子水平对深海贻贝在重金属环境长期暴露下的影响，剖析共生菌的作用。本研究将从共生的角度推进对深海生物环境适应性的解析，丰富对深海特殊生命过程的认知，为深海共生体系研究提供理论基础。

深海贻贝是深海热液和冷泉中的优势生物，共生是其适应深海独特环境的关键。深海热液区高重金属环境为研究双壳类环境适应性提供有利平台。由于样品的难获取和培养，国内外深海贻贝重金属适应机制的研究不深且未突出共生菌的作用。本项目以西太平洋化能生态系统中的优势种平端深海偏顶蛤为研究对象，基于前期建立的深海贻贝活体取样和长期培养体系，结合室内实验和野外调查开展深海贻贝重金属适应机制的研究。.通过室内重金属胁迫实验，结合细胞、生理、分子水平的数据发现在重金属胁迫下，深海贻贝鳃内和渗透压调节、能量代谢、核酸代谢、脂质代谢相关的通路发生改变；同时，在重金属胁迫下共生菌转录水平也发生显著的变化，共生菌中与氨基酸合成、能量代谢相关通路被富集；此外发现深海贻贝微管动力蛋白基因的表达与共生菌的数量显著相关，这些都暗示着共生菌通过氨基酸合成以及能量代谢为宿主提供能量，使其更好的抵御不利环境。但是随着胁迫时间的增加，深海贻贝体内的共生菌数量不断下降，深海贻贝生存生长受到挑战。.通过对西太平洋不同化能生态系统的野外调查，发现化能生态系统的重金属环境多样性，深海贻贝为了适应不同的环境，表现出不同的生理响应和重金属富集策略；此外发现基于深海贻贝体内重金属以及与重金属胁迫相关的生理指标，可以很好的把不同区域的深海贻贝区分开，说明深海贻贝是深海环境的重要指示生物。.本项目从共生的角度推进对深海生物环境适应性的解析，为深海共生体系研究提供理论基础。此外，本研究证实了深海贻贝能快速响应环境变化，是深海环境变化的指征生物，通过新组学技术，筛选了深海贻贝在室内重金属刺激下潜在的生物标志物，为后续监测深海矿产资源开发利用中可能带来的环境污染问题提供了研究思路，也为研究深海采矿重金属泄露对深海生物的影响以及建立可靠生物标志物体系提供理论基础。.项目执行期间发表SCI论文7篇，其中一作3篇，授权实验新型专利产品3项。

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