热胁迫下珊瑚组织中细菌群落的变化及其对珊瑚热耐受的作用

Coral reefs, the “rain forests of the sea,” are among the most biologically rich and productive ecosystems on earth. They also provide valuable ecosystem services that are vital to human society and industries. However, coral reefs face a wide and intensifying array of threats. Increased seawater temperature has already caused widespread damage to reefs, with coral bleaching and diseases. Given the global climate changes, the capacity of corals for acclimatization to heat stress is a critical component of their long-term survival. Bacteria in coral holobiont have been considered as a necessary component for increasing coral tolerance to future thermal stress. Nevertheless, it is presently far away from fully understanding of the contributions of bacteria to coral thermal tolerance. Based on the results obtained previously, we will simulate thermal stress, and will investigate the shifts in the bacterial community in the tissues of coral Pocillopora verrucosa under thermal stress. In combination with the responses of the coral to thermal stress, the correlation between bacteria and coral tolerance will be uncovered. According to the correlation analysis results, the key bacterial species (community), which significantly positive correlate to the coral thermal tolerance, will be determined. Through re-inoculation of these strains, we will detect the effect of them on the coral tolerance, and further verify the benefits provided by these key members. Moreover, the mechanisms involved in their contributions to enhancing the coral thermal tolerance will be comprehensively investigated. This work aims to reveal dynamics of the bacterial community in the coral tissues under thermal stress, and to elucidate the role of these bacteria in coral thermal tolerance. This will be helpful to understanding of the coral-bacteria relationship and developing and implementing coral reefs management and conservation programs under the stress of climate change.

珊瑚礁被誉为“海洋中的热带雨林”，是地球上生物多样性最丰富、生产力最高的生态系统之一，发挥着重要的生态系统服务功能。当前全球珊瑚礁面临着严峻的威胁。其中，海水温度升高导致的珊瑚白化或疾病，在全球范围造成大规模珊瑚礁退化。在全球气候变化的背景下，珊瑚对高温胁迫的耐受能力是其长期存活的关键。珊瑚“全功能体(holobiont)”中的细菌成员是决定珊瑚热耐受力的关键因素之一。然而，现阶段尚未清晰的认识细菌对珊瑚耐受热胁迫的贡献。基于前期工作，本项目设计模拟热胁迫实验，跟踪研究疣状杯形珊瑚组织中的细菌群落动态变化；解析珊瑚组织微生境中的细菌与珊瑚热耐受力的相关性，找到其中呈正相关的关键菌（群）；通过回接实验研究关键菌（群）对珊瑚热耐受力的影响，确证对珊瑚耐受热胁迫具有有益作用的关键菌（群），并进一步多角度研究其作用机制。本研究将深化对珊瑚—细菌相互关系的认识，为珊瑚礁保护计划的完善提供理论基础。

本项目围绕珊瑚共生体对热胁迫的响应及共生菌对珊瑚宿主高温耐受力的影响展开研究。建立了室内升温模拟实验系统，系统全面地研究了珊瑚、共生藻、共生细菌对升温的响应。揭示了升温过程中珊瑚、共生藻、共生细菌各自不同又相互关联的动态作用模式，以及高温引起珊瑚白化的过程和机制，阐明了高温胁迫下珊瑚共生菌群的结构变化，发现其中的关键共生菌类群如动物内生单胞菌、丙酸杆菌。通过共生菌两两拮抗实验，揭示温度变化显著改变珊瑚共生菌相互拮抗作用网络，表明温度是共生菌群群落构建的重要影响因素。通过对珊瑚共生细菌种内、种间群体感应信号分子的检测，揭示珊瑚共生细菌种间群体感应信号分子的产生响应共生藻和珊瑚宿主合成的化学物质DMSP，并推测珊瑚共生菌群可基于化学信号对水温变化做出群体响应。采用细菌与虫黄藻离体共培养体系，研究揭示了高温胁迫及受试共生菌的存在对虫黄藻CCMP 2433的生长产生了负面影响。回接实验表明丙酸杆菌菌株SCSIO 13291比动物内生单胞菌菌株SCSIO 12664对鹿角杯形珊瑚高温耐受力的影响更大。回接SCSIO 13291有助于珊瑚抵抗高温胁迫。研究成果有助于深化认识珊瑚共生体成员间的相互作用及其对升温的响应，为珊瑚微生物生态学提供新的理论认知，为基于菌群操作的珊瑚修复提供理论依据和菌种资源。.已发表研究论文5篇，其中SCI论文4篇，中文核心期刊论文1篇；获授权发明专利2件；获2019年广东省科技进步一等奖1项（项目负责人排名第4）。培养博士研究生1人，硕士研究生2人。项目负责人获广东省杰出青年基金项目支持。