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发挥着重要作用。过去几十年的研究也揭示了水生微生物显著的代谢灵活性，特别是现在已经清楚的是，许多水生原核生物既能够获取光能，又能够消耗有机物质(以下称为光异养生物)。这些替代的光营养途径尚未被常规方法捕获，但越来越多的证据表明，它们可能在水生生态系统中能量和碳的整体移动中发挥重要作用。在这里，我建议明确解决淡水中细菌光异养的规模和生态作用，最初侧重于好氧厌氧光营养细菌，随后将工作扩展到其他形式的细菌混合营养。该研究计划的主要目标是：1)量化淡水中光营养细菌丰度和活性的时空变异性；2)评估光营养细菌的系统发育组成、多样性和生物地理格局；3)探索调节光营养细菌分布和活性的环境和生物因素；4)探索这些途径在淡水中可能发挥的生态和生物地球化学作用。该计划将涉及范围广泛的淡水的大规模比较研究，以及小规模的实验操作，以评估光和其他环境因素对光养浮游细菌的分布和功能所起的作用。这项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。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的功能的范式。

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.