Quantitifaction of the metabolic proteins that drive biogeochmical cycles in marine systems

在海洋生态系统中，微生物中的酶催化元素循环的化学转化，并刺激生态系统中的能量流动。正是这些酶的丰度和效率决定了海洋系统中生化循环的速度。这些循环塑造了我们当前和未来的全球环境，因此，理解和准确模拟这些循环是环境科学家的一项重要任务，也是NERC使命声明的目标之一。人们刚刚开始了解这些海洋微生物组合令人望而生畏的复杂性。雄心勃勃的全球海洋测序计划(http://www.jcvi.org/research/gos/)，)等计划突显了这一挑战的规模，该计划虽然只完成了三分之一，但已经是有史以来投入公共领域的最大的元基因组数据集。在超过770万个DNA序列中，85%的组装序列数据是唯一的。这突出表明，海洋微生物群落在实验室培养收藏中仍然没有代表性，在遗传和生物化学方面也没有特征。当我们考虑到这种复杂性，以及微生物用肉眼看不见的事实时，准确描述对我们的环境有如此巨大影响的生化过程的挑战尤其明显。该项目旨在开发技术来补充这些基于速率的测量，并直接量化海洋样本中关键代谢蛋白的浓度，而不考虑其分类来源。这些蛋白质的浓度限制了正在研究的生物地球化学过程的能力，了解酶浓度的变化可以加深我们对海洋微生物群落功能的理解。将要开发的技术依赖于这样一个事实，即参与生物地球化学循环的酶在地球历史上很早就进化了，由于它们独特的化学成分，在地球上生命的进化过程中相对保持不变。因此，所有参与生物地球化学循环的微生物在蛋白质序列水平上都含有相同的保守酶，无论其分类如何。因此，已建立的特定蛋白质定量技术可以提供关于从复杂海洋系统中分离的样本中关键代谢酶总量丰度的宝贵信息。这种方法得益于这样一个事实，即微生物将大部分可用能量和原材料用于这些蛋白质的合成，因此酶复合体往往是细胞内的主要蛋白质产物，因此是大量量化的目标。该项目旨在将这些技术应用于计划于2009年进行的大西洋奖章样带巡航，该邮轮将提供一个在大西洋南北样带收集样本的平台，并将提供必要的辅助数据，包括生物速率测量和微生物群落结构。这些技术有能力描述和监测海洋微生物适应人为二氧化碳、紫外线和营养循环快速变化的能力，并绘制这些酶在全球范围内的分布图。

In marine ecosystems, enzymes in microorganisms catalyse the chemical transformations of elemental cycles and stimulate energy flow though the ecosystem. It is both the abundance and efficiency of these enzymes that determine the rates of biochemical cycles in marine systems. These cycles shape our current and future global environments, and the ability to understanding and accurately model these cycles is therefore an important task for environmental scientists and a goal of the NERC mission statement. The daunting complexity of these marine microbial assemblages is only beginning to be understood. The size of the challenge is highlighted by programs such as the ambitious Global Ocean Sequencing Project (GOS) (http://www.jcvi.org/research/gos/), which, although only one-third complete, already represents the largest metagenomic dataset ever put into the public domain. Of more than 7.7 million sequences of DNA, 85% of the assembled sequence data is unique. This highlights that the marine microbial community remains unrepresented in laboratory culture collections and uncharacterized both genetically and biochemically. When we consider this complexity together with the fact that microorganisms are invisible to the naked eye, the challenge of accurately characterising the biochemical processes that have such a huge impact on our environment is particularly apparent. This project aims to develop techniques to complement these rate-based measurements and directly quantify the concentrations of key metabolic proteins irrespective of taxonomic origin in marine samples. The concentrations of these proteins limit the capacity of the biogeochemical process being studied and knowledge of changes in enzyme concentrations can further our understanding of the function of marine microbial communities. The techniques to be developed rely on the fact that the enzymes involved in biogeochemical cycles evolved very early in the Earth's history and, owing to their unique chemistry, have remained relatively unchanged over the evolution of life on Earth. Therefore, all microorganisms that are involved in biogeochemical cycles contain the same conserved enzymes, at the level of protein sequence, irrespective of taxonomy. As a result, established techniques for the quantification of specific proteins can yield valuable information on the abundance of the total amount of key metabolic enzymes in a sample isolated from complex marine systems. This approach benefits from the fact that micororganisms devote a large proportion of available energy and raw materials to the synthesis of these proteins, such that the enzyme complexes are often the major protein products within the cell and thereby represent abundant targets for quantification. This project aims to implement these technologies on the forthcoming Atlantic Medorial Transect (AMT) cruise planned for 2009, which will provide a platform from which samples can be collected on a north/south transect of the Atlantic and will provide the necessary ancillary data, including biological-rate measurements and microbial community structure. These techniques have the capacity to characterise and monitor the capacities of marine micororganisms to acclimate to anthropogenic rapid change in CO2, UV and nutrient cycling, and to map the distributions of these enzymes on a global scale.