LTREB Renewal: Collaborative research: What controls long-term changes in freshwater microbial community composition?

DNA测序技术的进步使细菌等微生物的研究发生了革命性的变化，揭示了它们的遗传特性和生态潜力。微生物群落进行关键过程，调节重要营养物质和碳的数量和形式，这对地球上所有生态系统服务至关重要。该研究项目前五年的结果表明，这些群落的生物多样性和活动在不同的环境和时间里变化很大。微生物的生物多样性和生态系统功能受(1)影响生长的当地环境条件和(2)通过风和水的扩散控制。然而，这些因素的相对重要性仍然未知。本研究项目将对北极湖泊、溪流和土壤中微生物分布和活动的这两个基本控制因素进行描述，并将揭示气候变化如何影响微生物物种的季节性、年度和长期变化。这项研究将使用北极长期生态研究计划（LTER）产生的环境测量数据档案，并将使用下一代DNA测序技术来评估微生物群落的组成和功能。该研究项目的目标是测量与北极当前和剧烈环境变化相关的微生物多样性、细菌呼吸和生态系统功能的变化。细菌和其他微生物最终控制着吸热气体二氧化碳和甲烷的产生和消耗。在北极，变暖的气温正在融化永久冻土，暴露出土壤中大量先前冻结的有机碳。如果这些碳以吸热气体的形式释放到大气中，气候变暖的速度将会加快，进一步融化土壤，使更多的碳暴露于微生物的攻击之下。这种正反馈循环的强度是由细菌控制的，因为它们的呼吸作用将土壤中的碳转化为二氧化碳和甲烷，然后释放到大气中。此外，该项目将通过NSF本科生研究经验和教师研究经验项目，研究生和博士后科学家培训，以及与地球微生物组项目（http://www.earthmicrobiome.org）的合作，为教学和推广做出贡献。

Advances in DNA sequencing have revolutionized the study of microorganisms such as bacteria, revealing their genetic identity and ecological potential. Microbial communities carry out critical processes that regulate the amounts and forms of important nutrients and carbon, which are essential for all ecosystem services on Earth. Results from the first five years of this research program demonstrated that the biodiversity and activity of these communities varies tremendously among environments and over time. Microbial biodiversity and ecosystem functions are controlled (1) by local environmental conditions that affect growth, and (2) by dispersal via wind and water. However, the relative importance of these factors is still unknown. This research project will characterize these two fundamental controls on the distribution and activity of microbes in Arctic lakes, streams, and soils, and will reveal how seasonal, annual, and long-term shifts in microbial species are affected by climate change. This research will use the data archive of environmental measurements produced by the Arctic Long Term Ecological Research program (LTER), and will use next-generation DNA sequencing technology to assess microbial community composition and function.The goal of this research project is to measure shifts in microbial biodiversity, bacterial respiration, and ecosystem function associated with the current and dramatic environmental changes in the Arctic. Bacteria and other microbes ultimately control the production and consumption of the heat-trapping gases carbon dioxide and methane. In the Arctic, warming temperatures are thawing permafrost and exposing a vast store of previously-frozen organic carbon in soils. If this carbon is released to the atmosphere as heat-trapping gases the rate of climate warming will increase, further thawing the soils and exposing more carbon to microbial attack. The strength of this positive feedback loop is controlled by bacteria, because their respiration converts the soil carbon to carbon dioxide and methane which is then released to the atmosphere. In addition, this project will contribute to teaching and outreach through the NSF Research Experience for Undergraduates and Research Experience for Teachers programs, graduate student and postdoctoral scientist training, and collaboration with the Earth Microbiome Project (http://www.earthmicrobiome.org).