Collaborative Research: Controls Over Decomposition By Microbial Communities Under Climate Change

微生物，包括细菌和真菌，在全球碳循环中发挥关键作用的一种方式是将死去的植物物质再循环成营养物质和二氧化碳。虽然二氧化碳是植物生长所必需的，但它也是一种温室气体，所以地球上最微小的生命形式活动的变化可能会在全球范围内产生影响。反过来，温度升高可能会影响微生物的活动。如果气候变暖增加了微生物活动和二氧化碳的产生，那么可能会有一个正反馈，从而加剧环境变化的严重性。该项目的目的是研究温度变暖对土壤中微生物自然群落的影响。研究小组将使用尖端的实验和计算工具来分析微生物多样性的重要性。该项目的研究人员设计了一个实验来测试一种气候下的微生物在另一种气候下的表现。例如，他们将从凉爽潮湿的山顶移植微生物，并测量它们在沙漠中回收死亡植物物质的速度。山顶上的微生物缺乏在沙漠中生存所必需的基因是有道理的，而这些基因是沙漠微生物已经拥有的。为了测试这种可能性，研究人员将使用DNA测序来识别每种气候条件下几乎所有微生物中存在的基因。该研究还将测试是否所有微生物都是相同的，并在温度升高时加速它们的新陈代谢。研究人员将应用一个复杂的计算机模型来扩展他们的实验结果。该项目的广泛社会影响包括培训一名博士后研究员和四名研究生，新的计算基础设施，以及为加州州立公园的游客提供外展教育计划。学生和博士后培训将侧重于将微生物多样性与环境变化联系起来的跨学科研究。研究人员将把他们的计算机模型放到网上，这样科学界就可以很容易地获得这些模型。该项目将培养一名博士后科学家和四名研究生，开发计算基础设施，并为加州州立公园的游客建立一个外展教育计划。培训将侧重于将微生物生态学和基因组学与生态系统功能联系起来的跨学科研究。该项目的一个具体目标是开发一个基于网络的微生物群落模型，以便向科学界传播。在当地范围内，PIs将与加州大学欧文分校外展实习计划和非营利组织水晶湾联盟合作，为加州水晶湾州立公园的游客开发一个互动研究教育站。公园游客将有机会了解凋落物分解的生态系统过程以及气候变化背景下微生物多样性的后果。传统的生态系统模型假设生物地球化学速率与微生物群落组成无关，但新出现的经验证据与这一假设相矛盾。根据这一新证据，研究人员假设凋落物分解速率和对气候变化的反应取决于微生物群落组成。他们将通过控制微生物群落组成和在南加州的气候梯度上移植群落来验证这一假设。如果移植到同一地点的不同群落分解凋落物的速率不同，这一假设将得到支持。同样，不同微生物群落凋落物分解速率对气候变化的响应也不同。该项目还将分析微生物群落功能差异（或相似）的微生物特征。研究人员假设，不同微生物群落的分解率变化将由细胞外酶特性驱动。同样，微生物群落对气候变化响应的差异应该与“响应特征”的差异有关，例如耐旱和耐温性。这些假设将通过对凋落物微生物群落的宏基因组测序和利用生物信息学分析提取功能特征来验证。微生物群落的分类组成将通过细菌和真菌的16S和ITS标记的高通量测序进行量化。最后，研究人员的目标是检验他们的实验结果在未来气候变化预测下的后果。分子和生态系统数据将被纳入一个模拟模型，说明微生物群落组成。移植操作结果将与有和没有不同微生物群落的模型模拟进行比较，以测试组成对功能的重要性。根据模型选择程序，调查人员将模拟南加州气候变化情景下的凋落物分解。这些努力将揭示微生物群落组成对生态系统对未来气候变化的响应的影响。

One way that microbes, including bacteria and fungi, play a critical role in the global carbon cycle is by recycling dead plant matter into nutrients and carbon dioxide. Although necessary for plant growth, carbon dioxide is also a greenhouse gas, so changes in activities of the Earth's tiniest life forms could have affects on a global scale. Warming temperatures, in turn, could affect microbial activities. If warming increases microbial activities and carbon dioxide production, there could be a positive feedback that compounds the severity of environmental changes. The goal of this project is to study the effects of temperature warming on natural communities of microorganisms in soil. The research team will use cutting-edge experimental and computational tools to analyze the importance of microbial diversity. The project investigators have designed an experiment to test how well microbes from one climate do in another. For example, they will transplant microbes from a cool, wet mountaintop and measure how fast they can recycle dead plant matter in a desert. It's plausable that the mountaintop microbes will lack essential genes for survival in a desert - genes that desert microbes already have. To test this possibility, the investigators will use DNA sequencing to identify the genes present in nearly all of the microbes from each climate condition. The study will also test whether all microbes are equivalent and speed up their metabolism when the temperature rises. The investigators will apply a sophisticated computer model to extend their experimental findings. The broad societal impacts of this project include training for a postdoctoral researcher and four graduate students, new computational infrastructure, and an outreach-education program for visitors to a California state park. Student and postdoctoral training will focus on interdisciplinary research that links microbial diversity with environmental change. The investigators will make their computer models available on the Web so that they are easily accessible to the scientific community. This project will train a postdoctoral scientist and four graduate students, develop computational infrastructure, and establish an outreach-education program for visitors to a California state park. Training will focus on interdisciplinary research that links microbial ecology and genomics with ecosystem function. A specific aim of this project is to develop a web-based version of the microbial community model for dissemination to the scientific community. On the local scale, the PIs will partner with a University of California-Irvine outreach internship program and the non-profit Crystal Cove Alliance to develop an interactive research education station for visitors to Crystal Cove State Park, CA. Park visitors will have the opportunity to learn about the ecosystem process of litter decomposition and the consequences of microbial diversity in the context of climate change.Conventional ecosystem models assume that biogeochemical rates are independent of microbial community composition, yet emerging empirical evidence contradicts this assumption. In light of this new evidence, the investigators hypothesize that litter decomposition rates and responses to climate change depend on microbial community composition. They will test this hypothesis by manipulating microbial community composition and transplanting communities across a climate gradient in southern California. The hypothesis would be supported if different communities transplanted into the same location decompose litter at different rates. Similarly, the response of litter decomposition rate to climate variation across the gradient should vary for different microbial communities. This project will also analyze the microbial traits underlying differences (or similarities) in microbial community function. The investigators hypothesize that variation in decomposition rates across different microbial communities will be driven by extracellular enzyme traits. Likewise, variation in the microbial community response to climate change should relate to differences in 'response traits' such as drought and temperature tolerance. These hypotheses will be tested by sequencing the metagenomes of litter microbial communities and extracting functional traits using bioinformatics analyses. The taxonomic composition of the microbial communities will be quantified with high-throughput sequencing of 16S and ITS markers for bacteria and fungi. Finally, the investigators aim to examine the consequences of their experimental results under future climate change predictions. Molecular and ecosystem data will be incorporated into a simulation model that accounts for microbial community composition. The transplant manipulation results will be compared to model simulations with and without diverse microbial communities to test the importance of composition for function. Following a model selection procedure, the investigators will simulate litter decomposition under climate change scenarios in southern California. These efforts will reveal the consequences of microbial community composition for ecosystem responses to future climate change.