The competitive dynamics of toxic and non toxic ribotypes of the harmful dinoflagellate Alexandrium tamarense

有害甲藻亚历山大藻的有毒和无毒核糖体的竞争动态

• 批准号: NE/G011362/1
• 金额: $ 8.83万
• 依托单位: Scottish Association For Marine Science
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2009
• 资助国家: 英国
• 起止时间: 2009 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FG011362%2F1
• 关键词: competitive; dynamics; toxic; non; ribotypes

A number of species of marine phytoplankton produce natural biotoxins. Filter feeding shellfish ingest these phytoplankton without any apparent negative effects. However, bio-accumulation of the toxins in the shellfish flesh allows concentrations to reach sufficiency elevated levels that serious health consequences may result for humans that ingest the shellfish. Owing to the severity and possible fatality of the symptoms, paralytic shellfish poisoning (PSP) is perhaps the globally most important shellfish poisoning syndrome. PSP is caused by potent neurotoxins (saxitoxins) produced by the dinoflagellate genus Alexandrium. PSP occurs worldwide, with toxicity of shellfish in UK waters being characterised by frequent low level toxicity (monitoring programs indicating 100's of occurrences annually) and sporadic major toxicity events. Blooms of the causative species vary both spatially and temporally, and as yet we have very little understanding of the environmental factors that govern them. Human health is safeguarded by government biotoxin and phytoplankton monitoring programmes operated by Food Safety Authorities at significant cost to the economy. Of the various species of Alexandrium, the species complex Alexandrium tamarense is of particular concern in UK waters. Non toxic, group III, A.tamarense have historically been found in France, Spain and Portugal with their northernmost extent being the south of the UK. In contrast, toxic cells of group I A.tamarense are characteristic of northerly latitudes. However, recent studies have indicated changing distributions, with the non toxic group III cells now being found as far north as Shetland. Waters around the UK are known to be warming, suggesting that this, or other associated environmental changes (e.g. localised salinity, pH or light conditions), have allowed group III cells to 'invade' northern waters, where they now compete with group I. This is consistent with monitoring observations of reduced PSP events in recent years, but with no significant change in the total abundance of A.tamarense. Study of the factors driving the changing distributions of A.tamarense will provide better understanding and predictive ability of PSP events. This will allow more targeted biotoxin monitoring and better safeguard human health. Furthermore, such study will allow us to investigate how climate change is influencing the distribution of marine phytoplankton in UK waters. Recently we have isolated into laboratory culture strains of both group I and group III A.tamarense providing, for the first time, cultures of both toxic and non toxic strains of the organism from a single region. We shall study the influence of environmental conditions on strain growth and toxicity both individually and in competition. In addition, as A.tamarense forms an overwintering resting stage (a cyst) which settles to the sea floor and only germinates when conditions are favourable, we shall study the effect of environmental conditions on cyst germination. As both A.tamarense strains are of a single species, it is not possible to discriminate between them based on morphology. We will therefore utilise recently developed oligonucleotide probes for A.tamarense. After treatment with these molecular probes, and viewed under ultra violet light on a flourescence microscope, the non-toxic group III cells glow green and the toxic groups I cells glow gold, allowing for easy discrimination and enumeration even when cells are grown in combination to study their competition. Finally, we shall use our experimental results to derive and parameterise mathematical models for A.tamarense. These models will be used to simulate in situ data on the abundance of the different strains of A.tamarense we are currently collecting at a number of sites. Once developed, these models will increase our ability to predict the likelihood of a PSP event based on knowledge of the environmental conditions.

许多海洋浮游植物产生天然生物毒素。滤食性贝类摄入这些浮游植物没有任何明显的负面影响。然而，贝类肉中毒素的生物积累使浓度达到足够高的水平，这可能会对摄入贝类的人类造成严重的健康后果。由于症状的严重性和可能的​​致命性，麻痹性贝类中毒（PSP）可能是全球最重要的贝类中毒综合症。 PSP 是由亚历山大藻属产生的强效神经毒素（石房蛤毒素）引起的。 PSP 在世界范围内发生，英国水域贝类毒性的特点是频繁的低水平毒性（监测计划表明每年发生数百次）和零星的重大毒性事件。致病物种的水华在空间和时间上都有所不同，但迄今为止，我们对控制它们的环境因素知之甚少。人类健康受到食品安全当局实施的政府生物毒素和浮游植物监测计划的保障，但给经济造成了巨大损失。在各种亚历山大藻中，塔玛亚历山大藻复合体在英国水域尤其受到关注。无毒的 III 类 A.tamarense 历史上曾在法国、西班牙和葡萄牙发现过，其最北范围是英国南部。相比之下，I 类 A.tamarense 的毒性细胞是北纬地区的特征。然而，最近的研究表明分布正在发生变化，无毒的 III 族细胞现在远至设得兰群岛北部都被发现。众所周知，英国周围的水域正在变暖，这表明这种情况或其他相关的环境变化（例如局部盐度、pH 值或光照条件）使得 III 类细胞“入侵”北部水域，并在那里与 I 类细胞竞争。这与近年来 PSP 事件减少的监测结果一致，但 A.tamarense 的总丰度没有显着变化。研究驱动 A.tamarense 分布变化的因素将提供对 PSP 事件更好的理解和预测能力。这将使生物毒素监测更有针对性，更好地保障人类健康。此外，此类研究将使我们能够调查气候变化如何影响英国水域海洋浮游植物的分布。最近，我们分离出了 I 组和 III 组 A.tamarense 的实验室培养菌株，首次提供了来自同一地区的有毒和无毒菌株的培养物。我们将研究环境条件对菌株生长和毒性的影响，无论是个体还是竞争。此外，由于A.tamarense形成越冬休眠阶段（胞囊），沉降到海底并且只有在条件有利时才发芽，因此我们将研究环境条件对胞囊萌发的影响。由于两种 A.tamarense 菌株都属于单一物种，因此不可能根据形态来区分它们。因此，我们将利用最近开发的 A.tamarense 寡核苷酸探针。用这些分子探针处理后，并在荧光显微镜下观察，无毒的 III 族细胞发出绿色光，有毒的 I 族细胞发出金色光，即使细胞混合生长，也可以轻松区分和计数。研究他们的竞争。最后，我们将使用我们的实验结果来推导和参数化 A.tamarense 的数学模型。这些模型将用于模拟我们目前在多个地点收集的塔玛不同菌株丰度的现场数据。一旦开发出来，这些模型将提高我们根据环境条件知识预测 PSP 事件可能性的能力。