Linking bacterial community assembly and dissolved organic C dynamics along freshwater networks in boreal landscapes

细菌在所有水生系统的功能中起着重要作用。浮游和底栖细菌负责大部分的养分循环、有机物的转化和降解以及这些生态系统中很大一部分的总能量通量。当代微生物生态学的关键挑战之一是了解这些功能复杂且极其多样化的群落的结构因素。对于水生细菌群落，这意味着要了解我们观察到的微生物的起源，它们在相互关联的水生网络中的运动，以及它们在运输过程中遇到的各种环境条件的反应。目前的大多数研究缺乏这种动态的网络背景，因此提供了一个支离破碎和部分的水生细菌群落的观点。在这里，我提出了一个项目，将明确采取一个完整的网络方法来探索细菌群落的组装，在那里我们将重建沿着水生连续体发生的分类、代谢和功能微生物演替，从土壤到海洋，通过相互连接的河流和湖泊，并确定主要的潜在驱动因素。我们将同时评估在这个水生连续体中溶解有机碳库（DOC）的分子结构和反应性中发生的化学演为，目的是确定所有水生生态系统中这两个关键组成部分之间可能存在的联系和相互作用。仅在几年前，从技术和经济角度来看，这种水生细菌群落和有机C生物地球化学的综合分水岭视角是不可想象的，但现在新一代方法使我们能够以前所未有的细节和一小部分成本评估细菌和DOM的结构。拟议的项目将受益于一个正在进行的研究平台，该平台将提供一个大规模的、综合的河流、湿地和湖泊样本，沿着整个水生连续体在一个大型北方流域的quacimbec。我们将沿着这个连续体进行高空间分辨率的采样，并将结合高通量测序和基因组微阵列技术，细菌群落的代谢和生理测量，以及先进的分析方法来表征DOC的分子组成。拟议的工作是我们小组在过去十年中所做的研究的逻辑扩展，并将为理解复杂水生网络中细菌和有机池的组装，它们各自的环境控制以及它们之间可能存在的联系奠定基础。这项研究可能会导致对细菌演替、群落组装和资源链接的当前模型和范式的重新评估。

Bacteria play a major role in the functioning of all aquatic systems. Planktonic and benthic bacteria are responsible for much of the nutrient cycling, the transformation and degradation of organic matter and for a significant portion of the total energy flux in these ecosystems. One of the key challenges in contemporary microbial ecology has been to understand the factors of structure these functionally complex and extremely diverse communities. For aquatic bacterial communities, this implies understanding the origin of the microbes that we observe, their movement within the interconnected aquatic network, and their responses to the various environmental conditions that they encounter during transit. Most current studies lack this dynamic, network context, and therefore offer a fragmented and partial perspective of aquatic bacterial community assembly. Here I propose a program that will explicitly take a whole network approach to exploring bacterial community assembly, where we will reconstruct the taxonomic, metabolic and functional microbial successions that occur along the aquatic continuum, from soils to the sea through interconnected rivers and lakes, and identify the main underlying drivers. We will in parallel assess the chemical succession that occurs in the molecular structure and reactivity of the dissolved organic carbon pool (DOC) along this aquatic continuum, with the objective of determining the connections and interactions that may exist between these two key components of all aquatic ecosystems. This integrated watershed perspective of aquatic bacterial communities and organic C biogeochemistry was technically and financially unthinkable only a few years back, but is now enabled by new generation approaches that have increased our capacity of assessing the structure of both bacteria and DOM with unprecedented detail and at a fraction of the cost. The proposed program will benefit from an ongoing research platform that will provide a large-scale, integrated sampling of rivers, wetlands and lakes along the entire aquatic continuum in a large boreal watershed of Québec. We will carry out highly spatially resolved sampling along this continuum, and will apply a combination of high-throughput sequencing and genomic microarray technologies, metabolic and physiologic measurements of bacterial communities, and advanced analytical approaches to characterize the molecular composition of DOC. The proposed work is a logical expansion of the research that our group has done over the past decade, and will establish the foundation for understanding the assembly of both bacteria and organic pools within complex aquatic networks, their respective environmental controls, and the possible links that exist between them. The research will likely lead to a reassessment of current models and paradigms of bacterial succession, community assembly and links to resources.