IPY: Microbial winter survival physiology: a driver on microbial community composition and carbon cycling

摘要北极地貌变化很快。北极的“绿化”和“灌木化”推动气候反馈(通过反照率和能量交换)，并直接影响人类活动。然而，植被变化在地下是由养分可用性驱动的，这是微生物反馈的结果，这些反馈对气候系统也有独立的影响(例如二氧化碳和甲烷的排放)。因此，微生物系统在调节整个北极系统的运作方面起着关键作用。随着生物体在北极地区迁徙和扩散，它们所调节的过程也随之迁移。因此，预测冻土带生物地球化学模式的变化需要了解调节关键微生物组的分布和功能的因素。细菌和真菌仅仅受它们可获得的化学底物的调控，从而受到植物分布的调控吗？或者，微生物是否受到了忍受冬季冰冻条件的挑战的独立调控？微生物对低温的适应是什么？它们的生态后果是什么？对于基础微生物生态学来说，这些都是有趣的问题，但在北极变化的背景下，这些问题也很重要。该项目的核心假设是：1)特定微生物群的分布主要由植物群落组成控制，但2)适应冬季的挑战需要改变膜组成、低温保护剂和耐冻蛋白质，这些改变涉及微生物的生理成本，这些微生物对整个生态系统功能具有重要影响。假说将通过分析阿拉斯加(低北极)和格陵兰(高北极)地形序列中微生物分布和生理的模式，捕捉纬度和植物群落变化来验证。将使用克隆文库和定量遗传分析(QPCR)来评估微生物群落组成，以评估季节性变化(冻结前和冻结后、融化前和解冻后)。微生物膜化学(磷脂)和冷冻保护剂(氨基酸、海藻糖、多元醇)将通过化学分析进行评估。蛋白质生产模式的转变，包括抗冻蛋白、伴侣蛋白和其他，将使用蛋白质组学技术进行评估。这项工作将得到实验室研究的支持，这些研究评估了冰冻应激的特定方面：速率、温度和持续时间。它将通过与国际科学理事会合并网络的协作，与泛北极微生物种群动态的其他研究相结合。这将是第一次关于压力生理学如何调节微生物分布的研究。

AbstractArctic landscapes are changing rapidly. The "greening" and "shrubification" of the Arctic drive climate feedbacks (via albedo and energy exchange) as well as affecting human activities directly. Vegetation change, however, is driven belowground by nutrient availability, a result of microbial feedbacks that also have independent effects on the climate system (e.g. CO2 and CH4 emissions). The microbial system, therefore, plays a key role in regulating the functioning of the overall Arctic System. As organisms migrate and spread across the Arctic, the processes they regulate migrate with them. Predicting changes in the pattern of tundra biogeochemistry therefore requires understanding the factors that regulate the distribution and functioning of key groups of microbes. Are bacteria and fungi regulated simply by the chemical substrates available to them, and thus by plant distribution? Or alternatively, are microbes independently regulated by the challenges of tolerating the freezing conditions of winter? What are microbial adaptations to low temperature, and what are their ecological consequences? These are interesting questions for basic microbial ecology, but are also important in the context of the changing Arctic. The core hypotheses of this project are: 1) the distribution of specific microbial groups is controlled primarily by plant community composition, but 2) the challenge of acclimating to winter requires changes in membrane composition, cryoprotectants, and freeze-tolerance proteins that involve physiological costs to microbes that have important implications for overall ecosystem function. Hypotheses will be tested by analyzing patterns of microbial distribution and physiology across toposequences in Alaska (low Arctic) and Greenland (high Arctic), capturing latitude and plant community variation. Seasonal changes (pre- and post-freeze, pre- and post-thaw) will be assessed by using clone library and quantitative genetic analyses (QPCR) to evaluate microbial community composition. Microbial membrane chemistry (phospholipids) and cryoprotectants (amino acids, trehalose, polyols) will be assessed by chemical analyses. Shifts in protein production patterns, including anti-freeze proteins, chaperones, and others will be assessed using proteomic techniques. This work will be supported by laboratory studies evaluating specific aspects of freezing stress: rate, temperature, and duration. It will be integrated with other studies on pan-Arctic microbial population dynamics by collaboration with the ICSU MERGE network. This will be the first ever study on how stress physiology regulates microbial distributions.