The regulation and ecological importance of novel metabolic pathways in freshwater bacterial communities

细菌在所有水生系统的功能中起着重要作用。过去几十年的研究还揭示了水生微生物的显著代谢灵活性，特别是，现在已经清楚的是，许多水生原核生物能够收获光能和消耗有机物质（下文称为光异养生物）。这些替代的光养途径还没有被捕获的传统方法，但有越来越多的证据表明，它们可能在水生态系统中的能量和C的整体运动中发挥重要作用。我建议在这里明确地解决淡水中的细菌光合异养的规模和生态作用，最初专注于好氧无氧光合细菌，随后将工作扩展到其他形式的细菌兼养。该研究计划的主要目的是：1）量化淡水水体中光合细菌丰度和活性的时空变异性; 2）评估光合细菌的系统发育组成、多样性和地理分布模式; 3）探索调节光合细菌分布和活性的环境和生物因素; 4）研究淡水水体中光合细菌的分布和活性。以及4）探讨这些途径在淡水中可能发挥的生态和地球化学作用。该计划将涉及大规模的比较研究，在广泛的淡水和小规模的实验操作，以评估光和其他环境因素对光合浮游细菌的分布和功能的作用。拟议的工作将为理解淡水中这些微生物的环境控制和生态意义奠定基础，并将提供工具，有效地将这些生物及其相关的代谢途径纳入我们目前的淡水能量途径模型中。这项研究有可能从根本上改变目前关于湖泊中能量和碳的运动以及淡水食物网功能的范式。

Bacteria play a major role in the functioning of all aquatic systems. Research over the past decades has also revealed a remarkable metabolic flexibility of aquatic microbes, and in particular, it has now become clear that many aquatic prokaryotes are capable of both harvesting light energy and consuming organic materials (referred to as photoheterotrophs hereafter). These alternative phototrophic pathways have not been captured by conventional approaches, but there is increasing evidence that they may play a significant role in the overall movement of energy and C in aquatic ecosystems. I propose here to explicitly address the magnitude and ecological role of bacterial photoheterotrophy in freshwaters, initially focusing on aerobic anoxygenic phototrophic bacteria, and subsequently extending the work to other forms of bacterial mixotrophy. The main objectives of the research program are: 1) to quantify the spatial and temporal variability of phototrophic bacterial abundance and activity in freshwaters; 2) to assess the phylogenetic composition, diversity and biogeographical patterns of phototrophic bacteria; 3) to explore the environmental and biological factors that regulate the distribution and activity of phototrophic bacteria; and 4) to explore the ecological and biogeochemical role that these pathways may play in freshwaters. The program will involve large-scale comparative studies across a wide range of freshwaters and also small-scale experimental manipulations to assess the role that light and other environmental factors play on the distribution and functioning of phototrophic bacterioplankton. The proposed work will establish the foundation for understanding the environmental controls and ecological significance of these microbes in freshwaters, and will provide the tools to effectively incorporate these organisms and their associated metabolic pathways into our current models of energy pathways in freshwaters. This research has the potential to fundamentally shift the current paradigms concerning the movement of energy and carbon in lakes, and the functioning of freshwater food webs.