我国南海北部湾贝类体内Gymnodimine毒素的溯源与代谢转化研究

In recent years, the contamination of shellfish seafood products by phycotoxins has become an increasingly serious issue in China. Multiple toxins have now been widely detected in shellfish samples collected along the Chinese coast. Results to date have shown that the cyclic imine toxin, Gymnodimine (GYM), was detected in all shellfish samples collected from Beibu Bay in the South China Sea, with GYM levels in this region being the highest of all samples collected from the Chinese coast. Considering this information this project will focus on Beibu Bay as the investigative zone and focus a number of research activities as follows: first, the spatial and temporal distribution of GYM in shellfish will be explored through periodical and continuous monitoring of local shellfish samples; second, possible GYM producing microalgae such as Karenia selliformis and Alexandrium ostenfeldii will be isolated from the sea areas with high concentrations of the toxins occurring in shellfish samples during high-occurrence season, and the toxin-producing characteristics will be explored through batch culture of isolation strains; third, simulation experiments for GYM accumulation by mussels, oysters, and clams will be carried out in a laboratory setting, and the metabolic profiling of GYM toxins in shellfish will be conducted by LC-MS/MS and using low- and high-resolution platforms; finally, using mussels (Mytilus galloprovincialis) as a model organism the variation of GYM and its metabolites will be monitored during accumulation and depuration processes following feeding on a known GYM-producing strain K. selliformis currently in culture in our laboratory. Meanwhile, the relationship between GYM biotransformation and lipid metabolism will be discussed through monitoring of the variation of fatty acid composition in this experiment period. In summary the aim of this project is to identify and characterize GYM-producing microalgae from Beibu Bay in the South China Sea, and to obtain a better understanding of GYM uptake and metabolism in a variety of shellfish species that are important to the region.

近年，我国养殖贝类积累藻毒素的问题日趋严峻，潜在威胁消费者健康。申请人近期调查显示，南海北部湾采集的贝类均含Gymnodimine（GYM）毒素，最高含量高达211 µg/kg。本项目选择北部湾为研究海区，通过定期连续监测，探明贝类积累GYM的时空分布规律；选择贝类染毒的高发季节和养殖海区，重点监测并分离培养Karenia selliformis、Alexandrium ostenfeldii等可能的产毒藻株，并探讨其产毒特征及影响因素；通过室内培养现有的GYM产毒藻株K. selliformis，模拟紫贻贝、牡蛎和文蛤滤食甲藻积累GYM的过程，并分析毒素的代谢轮廓；模拟并监测GYM及其代谢物在紫贻贝染毒和排毒过程中的动态变化，结合贝类脂肪酸组成的分析，探讨毒素转化与脂质代谢之间的响应关系。以期揭示北部湾GYM的生物来源及其产毒特征，阐释贝类体内GYM的代谢轮廓及其对贝类脂肪酸组成的影响。

受全球气候变化和水体富营养化的影响，海洋有毒藻的高密度生长或藻华现象频发，导致贝类积累藻毒素的问题日益突出。近年，我国沿海贝类样品中普遍检出环亚胺裸甲藻毒素（gymnodimine, GYM），且在我国南海北部湾贝类样品中积累的浓度相对较高，潜在威胁消费者健康。.项目在北部湾近岸海域定期采集了两周年的贝类样品，发现GYM-A毒素的检出率最高，其次是软骨藻酸（DA）和环亚胺毒素SPX1，且GYM-A在秋冬季节浓度较高，DA在夏季浓度较高。通过对北部湾近岸海域和离岸大面站位的浮游植物种类和毒素的调查分析，发现北部湾的GYM-A主要来自鞍状凯伦藻（Karenia selliformis），但不排除奥氏亚历山大藻（Alexandrium ostenfeldii）的贡献，DA主要来自船斑菱形藻（Nitzschia navis-varingica）。项目在广东和海南沿海、南海西部海域实施了四个航次的大面站位浮游植物调查，检出GYM-A、PTX2、hYTX、DA及PSP等毒素，其中GYM-A和PTX2在四个航次均有检出，且PTX2的分布范围较广，hYTX和DA的分布相对集中，且DA毒素主要在珠江口临近的广东近海分布。结合浮游植物的种类鉴定与分析结果推断，DA主要来自尖细伪菱形藻（Pseudo-nitzschia cuspidata），hYTX可能来自具刺膝沟藻（Gonyaulax spinifera）。项目在北部湾分离构建了红色赤潮藻、相关亚历山大藻、米氏凯伦藻、链状亚历山大藻、垂裂莱万藻等38株有毒有害微藻的单克隆藻株。.项目通过模拟不同贝类滤食GYM-A产毒藻和贝类直接与水体中GYM-A暴露接触的染毒方式，系统探究了GYM-A的积累转化及其对贝类脂质代谢的影响。研究发现贝类滤食积累的藻毒素在消化腺中浓度最高，而暴露接触积累的毒素在鳃组织中的浓度最高。紫贻贝、牡蛎、文蛤、毛蚶、菲律宾蛤仔等双壳贝类积累的GYM-A均与脂肪酸快速发生酯化反应，毒素主要以GYM-A酯化物形式存在；不同脂肪酸与GYM-A发生酯化反应的亲和力不同，受酶催化的影响，不同贝类具有种间差异。通过代谢组学和脂质组学分析，发现牡蛎体内GYM-A毒素酯化反应消耗脂肪酸并影响其脂质代谢过程。.本研究为深入认识北部湾海域GYM-A毒素对贝类水产品食用安全和生态系统健康的风险提供了重要参考，对保护消费者健康具有重要意义。