The physiologic and phylogenetic basis of patterns in bacterial community metabolism in aquatic ecosystems

异养细菌在所有水生系统的功能中发挥着重要作用。浮游细菌负责这些生态系统中的大部分营养循环、有机物质的转化和降解以及总能量通量的很大一部分。虽然我们现在对水生生态系统中微生物碳和营养物质代谢的广泛模式以及塑造它们的环境因素有了相对较好的了解，但我们仍然不了解这些模式实际上是如何产生的。例如，我们仍然不知道在湖泊和其他系统中观察到的群落代谢变化在多大程度上是共存细菌群的激活和失活的结果，或者是具有不同内在代谢能力的其他细菌群取代现有细菌群的结果。这代表了我们目前对水生微生物群落的功能和调节的理解中的一个主要差距。拟议的研究的中心目标是建立在群落碳代谢模式的生理和系统发育的基础上，在浮游细菌群落沿着环境梯度，特别是在过渡带和生态交错带。拟议的研究结合了分子生态学的先进技术，基于流式细胞术和细胞分选的单细胞方法，社区水平的代谢测量和有机碳生物地球化学。采样方法将是动态的，重点是这些微生物群落在沿着整个流域以及在关键界面和主要环境特征之间移动时如何变化和反应。该计划的长期目标是弥合我们对细菌群落代谢，组成和群落生理结构之间存在的联系的理解的主要差距，以及这些反过来如何影响水生生态系统中的生物地球化学功能。这项研究将推进我们对水生生态系统功能的基本理解，但它也对生态学和进化中有关多样性与生态系统功能之间联系的更广泛问题具有重大影响，这些问题是当前激烈研究和辩论的主题。

Heterotrophic bacteria play a major role in the functioning of all aquatic systems. Planktonic bacteria are responsible for much of the nutrient cycling, for the transformation and degradation of organic matter and for a significant portion of the total energy flux in these ecosystems. While we now have a relatively good idea of the broad patterns in microbial carbon and nutrient metabolism in aquatic ecosystems, and of the environmental factors that shape them, we still do not understand how these patterns are actually generated. For example, we still do not know to what extent changes in community metabolism observed in lakes and other systems are the result of the activation and inactivation of coexisting bacterial groups, or to the replacement of existing groups by others with different intrinsic metabolic capabilities. This represents a major gap in our current understanding of the functioning and regulation of aquatic microbial communities. The central goal of the proposed research is to establish the physiological and phylogenetic basis of the patterns in community carbon metabolism in planktonic bacterial communities along environmental gradients and especially in transition zones and ecotones. The proposed research combines advanced techniques in molecular ecology, single-cell approaches based on flow cytometry and cell-sorting, metabolic measurements at the community level, and organic carbon biogeochemistry. The sampling approach will be dynamic, focusing on how these microbial communities change and react as they move along entire watersheds, and across critical interfaces and major environmental features. The long-term goal of this program is to bridge the major gap in our understanding of the links that exist between bacterial community metabolism, composition and the physiological structure of the community, and how these in turn influence biogeochemical function in aquatic ecosystems. This research will advance our basic understanding of the functioning of aquatic ecosystems, but it also has major implications to broader questions in Ecology and Evolution concerning the links between diversity and ecosystem function, current topics of intense research and debate.