ORCC: Do multi-species biofilms accelerate microbial evolution under extreme warming?

为了保护社会免受气候变化的危害，需要了解气候变化的进展速度有多快，以及全球区域将如何受到影响。目前，对土壤在气候变化中的作用的不完全了解阻碍了预测。土壤中的碳比大气和全球所有植被的总和还要多。当微生物分解土壤碳时，它们会向大气中释放二氧化碳--一种温室气体。在全球范围内，这一过程每年产生的二氧化碳是化石燃料燃烧的10倍。微生物如何适应气温升高还不是很清楚，因此，它们在气温上升时对温室效应的贡献也不清楚。此外，微生物繁殖速度很快，目前还不清楚随着气候变化的进展，它们是否会进化产生更多或更少的二氧化碳。很少有研究进行进化实验来解决这个问题，也没有研究在一个完整的微生物群落内进化出室外生态系统中的微生物。在这项研究项目中，某些种类的真菌和细菌将单独或与自然微生物群落一起暴露在极端变暖中，以确定微生物是否在自然微生物群落中进化出更好的工具，如生物膜，以及适应是否导致极端变暖下土壤碳分解速率的保持或增加，这可能会加速气候变化。更广泛的影响包括培养本科生、研究生和博士后学者。PIS还将开发一个中学教育模块，其中包括了解微生物和气候变化的动手活动。来自低收入和代表性不足人群的中学生和教师将参与这一项目。在现实世界中，土壤真菌和细菌将无法孤立地适应气候变化。事实上，真菌和细菌经常相互作用，形成多物种生物膜。在这个项目中，将研究极端变暖响应生物膜形成的生态进化机制，并将研究这将如何影响大规模的有机碳分解。因此，这项研究将提供对土壤微生物如何适应气候变化的更深层次的理解，从而改进未来气候情景下的预测。PI假设，如果真菌和细菌相互作用，它们将更有效地适应极端变暖。具体地说，极端变暖将选择生物膜的形成，因为生物膜的胞外聚合物(EPS)可以缓冲微生物免受热损害。此外，在多物种生物膜内适应极端变暖将导致更快的有机C分解，因为EPS可以提高环境中有机C降解酶的寿命和效率。数以千计的细菌和真菌菌株将在田间暴露在极端变暖的环境中，同时控制它们与整个微生物群落的相互作用，并控制它们形成多物种生物膜的能力。为了重点研究适应的基本机制，将进行基于计算机的生态系统建模和与实地相同的实验设计的实验室研究。在每种情况下，都将监测极端变暖下的生长速度、存活率、生物膜形成和有机碳分解。该项目还将评估霓虹灯场地土壤样本中EPS的产生，这些土壤样本代表了许多不同的陆地栖息地和广泛的环境条件，从而扩大了研究的普遍性。该奖项由综合组织系统和生物科学局环境生物学部门共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

To protect society from the hazards of climate change, how quickly climate change will progress and how global regions will be affected needs to be understood. Currently, predictions are hampered by incomplete knowledge about the role of soils in climate change. Soils harbor more carbon than the atmosphere and all global vegetation combined. As microbes decompose soil carbon, they release CO2—a greenhouse gas—to the atmosphere. Globally, this process produces 10 times as much CO2 each year than fossil fuel burning. How microbes adapt to increasing temperatures is not well-understood and thus, their contribution to the greenhouse effect as temperatures rise is not clear. Also, microbes reproduce quickly, and it is not clear if they will evolve to produce more or less CO2 as climate change progresses. Few studies have conducted evolution experiments to address this question, and none have evolved microbes in outdoor ecosystems within an intact microbial community. In this research project, certain species of fungi and bacteria will be exposed to extreme warming, either in isolation, or with the natural microbial community, to determine whether microbes evolve better tools, such as biofilms, in a natural microbial community, and whether adaptation results in maintenance or increase in soil carbon decomposition rates under extreme warming, which would potentially accelerate climate change. Broader impacts include training of undergraduate, graduate, postdoctoral scholars. The PIs will also develop a middle school educational module that includes hands-on activities to learn about microbes and climate change. Middle-school students and teachers from low-income and underrepresented populations will be involved in this project.In the real world, soil fungi and bacteria will not adapt to climate change in isolation. In fact, fungi and bacteria often interact to form multi-species biofilms. In this project, eco-evolutionary mechanisms of biofilm formation in response to extreme warming will be examined and how this will impact large-scale organic C decomposition will be studied. This research will thus provide a deeper understanding of how soil microbes adapt to climate change, and, thus, improve predictions under future climate scenarios. The PIs hypothesize that fungi and bacteria will adapt to extreme warming more effectively if they interact with one another. Specifically, extreme warming will select for biofilm formation because extracellular polymeric substances (EPS) of biofilms can buffer microbes from heat damage. In addition, adaptation to extreme warming within multi-species biofilms will result in faster organic C decomposition since EPS can improve the longevity and efficiency of organic C-degrading enzymes in the environment. Thousands of generations of bacterial and fungal strains will be exposed to extreme warming in the field while manipulating their interactions with the whole microbial community and controlling their ability to form multi-species biofilms. To focus on mechanisms underlying adaptation, computer-based ecosystem modeling and lab studies with the same experimental design as the field will be performed. In each case, growth rate, survivorship, biofilm formation, and organic C decomposition under extreme warming will be monitored. This project will also assess EPS production in soil samples from NEON sites which represent many different terrestrial habitats with a wide range of environmental conditions, thus broadening the generalizability of the research.This award was co-funded by Integrative Organismal Systems and the Division of Environmental Biology in the Directorate for Biological Sciences.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.