MICRO-CYCLE: Unravelling the role of microbial genomic traits in organic matter cycling and molecular composition along the river continuum

全球生物地球化学循环描述了碳和其他营养物质在地球系统主要组成部分之间的转化和运输。河流和溪流是这一循环的主要组成部分，将有机物质(OM)形式的碳(C)和其他营养物质(氮、氮、磷、磷)在陆地环境与大气和海洋之间的流动联系在一起。河流和溪流中的细菌每毫升水中的细菌数量可以达到数百万个细胞和数千个物种(称为浮游细菌)，它们利用OM及其包含的碳、氮和磷作为生长和呼吸的食物来源。OM池包含类似的不同范围的化合物，有数万个分子，不同的C、N、P和其他化学成分存在于各种不同的化学结构中。细菌对不同形式的OM有偏好，与这些不同的结构和内容有关，但我们对哪些细菌利用哪些OM分子知之甚少。这一点很重要，因为来自陆地生态系统的有机物在从河流源头向下游河段、河口和海洋的运输过程中，在浓度和化学结构上都发生了变化。细菌群落和有机质之间的相互作用在决定有多少C、N和P被释放到海洋中以及有多少C、N和P被以二氧化碳或氮气的形式呼吸释放到大气中起着关键作用。微循环项目旨在更好地了解浮游细菌在利用和修改OM方面所起的作用，因为它们都从河流的源头流向海洋(称为河流连续体)。这种生态过程的新知识决定了河流中存在哪些类型的细菌，这种变化在不同的源头和海洋中是如何变化的，以及这对OM的使用和沿河流的运输意味着什么，这将帮助我们创建能够更好地预测河流如何发挥作用以及它们未来可能如何变化的模型。我们将通过填补以下方面的知识空白来实现这一点：1.浮游细菌群落在整个河流连续体中的结构机制，从河流的源头到下游。这将通过代表不同景观和水文特征的泰晤士河及其子流域的空间结构抽样来实现。哪些细菌(细菌群落)在利用有机质方面发挥了积极作用，哪些物种只是“经过”而在功能上对OM循环没有贡献(以及这种循环在河流连续体中如何随环境波动而变化)。有机质的化学成分在决定河流连续体细菌群落的结构和功能中的作用，以及细菌群落在改变有机质的化学成分中的作用。研究河流连续体上细菌的生态和功能结构，以及细菌群落和有机质之间的关系，以建立细菌如何控制河流新陈代谢以及向大气输出C和N以及向海洋输出C、N和P的预测模型。

Global biogeochemical cycles describe the transformation and transport of carbon and other nutrients between the major components of the Earth system. Rivers and streams represent a major component in this cycle, linking flows of carbon (C), in the form of organic matter (OM), and other nutrients (nitrogen, N; phosphorus, P) between the terrestrial environment and the atmosphere and oceans. Bacteria in rivers and streams, which can number in the millions of cells and thousands of species per millilitre of water (called bacterioplankton), use OM and the carbon, nitrogen and phosphorus it contains, as a source of food, both for growth and for respiration. The OM pool contains a similarly diverse range of compounds, with tens of thousands of molecules, with varying C, N, P and other chemical constituents held in a wide variety of different chemical structures. Bacteria have preferences for different forms of OM, linked to these differing structures and contents, but we know little about which species of bacteria exploit which OM molecules. This is important, as the OM from terrestrial ecosystems is changed in both concentration and chemical structure during transport from the headwaters of a river to downstream reaches, estuaries and the sea. The interactions between the bacterial community and OM play a critical role in determining how much C, N and P are released into the oceans and how much is respired as carbon dioxide or released as nitrogen gas to the atmosphere.The MICRO-CYCLE project seeks to better understand the role that bacterioplankton play in using and modifying OM as they both flow from the headwaters of rivers towards the sea (called the 'river continuum'). This new knowledge of the ecological processes that determine what types of bacteria are present in rivers, how this varies from headwaters to the sea, and what this means for how OM is used and transported along rivers, will help us create models that can better predict how rivers function, as well as how they might change in future.We will do this by filling the gaps of knowledge in:1. The mechanisms by which bacterioplankton communities are structured across the river continuum, from headwaters to the lower reaches of rivers. This will be achieved by spatially structured sampling across the River Thames and its sub-catchments representing different landscape and hydrological characteristics.2. Which species of bacteria (the bacterial community) play an active role in using OM and which species are just 'passing through' and not contributing functionally to OM cycling (and how this varies along the river continuum in response to environmental fluctuations).3. The role that the chemical composition of OM has in determining the structure and function of the bacterial community along the river continuum, and the role that the bacterial community has in changing the chemical composition of OM.4. The ecological and functional structure of bacteria along the river continuum, and the relationships between bacterial communities and OM, to build predictive models of how bacteria control the metabolism of rivers and the export of C and N to the atmosphere and C, N and P to the oceans.