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

全球地球化学循环描述了地球系统主要组成部分之间碳和其他营养物质的转化和输送。河流和溪流是这一循环的主要组成部分，将陆地环境与大气和海洋之间以有机物（OM）形式存在的碳（C）和其他营养物质（氮，N;磷，P）的流动联系起来。河流和溪流中的细菌，每毫升水中有数百万个细胞和数千个物种（称为浮游细菌），使用OM及其所含的碳，氮和磷作为食物来源，用于生长和呼吸。OM池包含类似的多种化合物，具有数万个分子，具有不同的C，N，P和其他化学成分，具有各种不同的化学结构。细菌对不同形式的OM有偏好，这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，因为陆地生态系统中的有机物在从河流源头向下游、河口和海洋输送的过程中，其浓度和化学结构都发生了变化。细菌群落和有机质之间的相互作用在决定有机质中有多少C，氮和磷被释放到海洋中，有多少以二氧化碳的形式被呼吸，有多少以氮气的形式被释放到大气中。微循环项目旨在更好地了解浮游细菌在利用和改变有机质方面所起的作用，因为它们都是从河流的源头流向海洋（称为“河流连续体”）。这些关于生态过程的新知识决定了哪些类型的细菌存在于河流中，从源头到海洋的变化，以及这对OM如何使用和沿着河流运输意味着什么，这将有助于我们创建模型，更好地预测河流的功能，以及它们未来可能如何变化。我们将通过填补以下知识空白来做到这一点：1.浮游细菌群落在河流连续体中的结构机制，从河流的源头到下游。这将通过在泰晤士河及其代表不同景观和水文特征的子流域进行空间结构化采样来实现。哪些种类的细菌（细菌群落）在利用有机质方面发挥着积极作用，哪些种类只是“路过”而不是对有机质循环起作用（以及这是如何随着环境波动而沿着河流连续体变化的）。3. OM的化学组成在决定细菌群落结构和功能方面的作用沿着河流连续体，以及细菌群落在改变OM的化学组成方面的作用。河流连续体中沿着细菌的生态和功能结构，以及细菌群落与有机质之间的关系，以建立预测模型，研究细菌如何控制河流的代谢以及C和N向大气的输出和C，N和P向海洋的输出。

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.