Distinguishing pollutant-induced stresses from spatial and temporal environmental heterogeneity - a metabolomic approach to stress ecology

如果说蛋白质形成了细胞的机器，那么小分子代谢物就是细胞的通货，形成了信息流(信号)、能量和营养物质，调节了许多最重要的生物功能。对这些代谢物的核算--通过以公正的方式列出生物样本中存在的所有代谢物--被称为代谢组学。由于代谢在生理控制中的中心性质，细胞和生物体中存在的代谢物对环境变化(如土壤化学、气候等方面的差异)非常敏感。近年来，分析方法的发展为识别存在于细胞中的代谢物的一大子集提供了希望，这种分析可以用来确定哪些环境影响正在影响生物体的健康。这一点很重要，因为人类活动现在意味着，在许多发达国家，以及越来越多的发展中国家，环境条件已经改变，这意味着物种生活在不再“原始”的生态系统中。人类对环境的影响的一个例子是，在许多发达国家，以及越来越多的发展中国家，存在着由家庭和工业污染造成的污染的“灰色面纱”。到目前为止，代谢组学方法主要用于实验室研究，以确定一系列物种对环境胁迫的反应。这些压力包括污染，以及极端温度和疾病等“自然”因素。虽然这些结果非常有希望，但潜在的批评是，它在现实世界中可能没有在实验室中那么成功。这主要是因为在自然环境中，环境因素(例如气候、土壤/水化学、与其他生物的相互作用)有很大的变化，这些因素也都会影响代谢物的水平。这可能使我们很难(如果不是不可能)将正在研究的因素(例如环境污染)的影响与所有其他不同环境因素的影响所产生的“代谢噪音”区分开来。在这个项目中，我们的目标是专门测试代谢组学如何能够可靠地研究土壤污染对自然种群的影响。我们将研究一种常见的英国蚯蚓：蚯蚓是土壤污染的良好‘哨兵’物种，因为它们对污染敏感，并在大多数土壤中发挥重要的生态作用。最初，我们将在一年中的几个不同时间从全国各地的广泛清洁地点采集蠕虫样本。这将告诉我们在相对没有污染的条件下生活的蠕虫的代谢反应的多样性。接下来，我们将进行一系列的实验室实验，以了解一系列环境因素(如不同的土壤酸度、水分水平、土壤类型、温度)对蠕虫代谢生理的影响。这将帮助我们解释我们在现场收集的个体中看到的变化：他们处于什么样的自然压力之下？最后，我们将测量从一组已知污染地点(被有毒重金属和/或有机化学品污染)在一年中的不同时间收集的蠕虫的代谢物。这将使我们能够回答一个根本的问题，即使收集蠕虫的地点本身和收集时的气候条件千差万别，我们能否可靠地将蠕虫与清洁和受污染的地点区分开来？完成后，我们的研究将提供一个广泛和高质量的数据集，可以用作未来研究的基线。此外，我们将获得的结果将对生理学家和环境科学家都具有相当大的学术兴趣。最后，从长远来看，我们的结果可能会导致开发监测和评估环境变化状况的方法。

If proteins form the machinery of a cell, then small molecule metabolites are the cell's currency, forming the flows of information (signalling), energy and nutrients that regulate many of the most important biological functions. The accounting of these metabolites - by listing in an unbiased fashion all the metabolites present in a biological sample - is called metabolomics. Because of the central nature of metabolism in the control of physiology, the metabolites that are present in cells and organisms are very sensitive to environmental variation (e.g. differences in soil chemistry, climate, etc.). In recent years, the development of analytical methods to identify a large sub-set of the metabolites present in cells has held promise that such analyses could be used to establish which environmental influences were affecting an organism's health. This is important because human activity now means that in much of the developed, and increasingly the developing, world, the condition of the environment has been changed meaning that species are living within ecosystems that are no longer 'pristine'. One example of the effects of man on the environment is the presence in much of the developed and, increasingly, developing world, of a 'grey veil' of contamination resulting from domestic and industrial pollution. To date the metabolomics approach has been used mostly in laboratory-based studies to identify the responses of a range of species to environmental stresses. These stresses include pollution, as well as 'natural' factors like temperature extremes and disease. While these results have been extremely promising, a potential criticism is that it may not be as successful in the real world as it is in the lab. This is primarily because in the natural environment there are large variations in environmental factors (e.g. climate, soil/ water chemistry, interactions with other organisms), which will all also affect metabolite levels. This may make it difficult, if not impossible, to separate the effects of the factor being studied (e.g. environmental pollution) from the 'metabolic noise' created by the effects of all the other varying environmental factors. In this project we are aiming to specifically to test how reliable metabolomics can be to study the effects of soil pollution on natural populations. We will study a common British earthworm species: earthworms are good 'sentinel' species for soil contamination, as they .are both sensitive to pollution, and play an important ecological role in most soils. Initially, we will sample worms at several different times throughout the year from a wide range of clean sites across the country. This will tell us about the variety of metabolic responses that can be found in worms living under comparatively unpolluted conditions. Next we will conduct a series of laboratory experiments to understand the effects of a range of environmental factors (e.g. different soil acidity, moisture levels, soil type, temperature) on worm metabolic physiology. This will help us interpret the variations we see in our field-collected individuals: what kind of natural stresses were they under? Finally we will measure metabolites in worms collected from a set of known polluted sites (contaminated with toxic heavy metals and/or organic chemicals) at different times through the year. This will allow us to answer the fundamental question, can we reliably distinguish worms from clean and polluted sites, even though the sites themselves and the climatic condition at the time of collections are highly varied? On completion, our study will provide an extensive and high-quality dataset that could be used as a baseline for future research. Further, the results we will obtain will be of considerable academic interest to both physiologist and environmental scientists. Finally our results may, in the long run, lead to the development of methods to monitor and assess the changing state of our environment.