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发挥着重要作用。浮游和底栖细菌负责这些生态系统的大部分营养循环、有机物的转化和降解以及总能量通量的很大一部分。当代微生物生态学的关键挑战之一是理解这些功能复杂和极其多样化的群落的结构因素。对于水生细菌群落，这意味着了解我们观察到的微生物的来源，它们在相互连接的水生网络中的运动，以及它们对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、网络的背景，因此提供了一个关于水生细菌群落聚集的零散和局部的视角。在这里，我提出了一个计划，明确地采用整个网络的方法来探索细菌群落组装，其中我们将重建发生在水生连续体上的分类、代谢和功能微生物演替，从土壤到海洋，通过相互关联的河流和湖泊，并确定主要的潜在驱动因素。我们将同时评估沿这一水生连续体的溶解有机碳库(DOC)的分子结构和反应性中发生的化学演替，目的是确定所有水生生态系统的这两个关键组成部分之间可能存在的联系和相互作用。仅仅几年前，这种水生细菌群落和有机碳生物地球化学的综合分水岭观点在技术上和经济上都是不可想象的，但现在由于新一代方法的支持，我们以前所未有的细节和一小部分成本提高了我们评估细菌和DOM结构的能力。拟议的项目将受益于一个正在进行的研究平台，该平台将对魁北克北部一个大型分水岭的整个水域连续体的河流、湿地和湖泊进行大规模、综合的采样。我们将沿着这一连续体进行高度空间分辨率的采样，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研究的合乎逻辑的扩展，并将为了解细菌和有机池塘在复杂的水生网络中的组装、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现有模式和范例的重新评估。

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.