Collaborative Research: Ecophysiology of Deeply-Branching Bacterial and Archaeal Communities

从分子系统发育研究中产生的最深刻的发现之一是，“宇宙生命之树”在其最深处的分支中完全由嗜热生物居住。关于为什么会这样，有两种相反的理论：生命首先出现在热液环境中，可能在地下深处。嗜热生物优先在冥古宙地球的“晚期重轰炸”中幸存下来。由于这一时期没有沉积记录，因此不可能直接通过地质学来解释这些理论。相反，我们必须着眼于现代地球微生物过程，以更好地理解对嗜热生命的控制和模式。有了这种认识，地质记录最终可能会产生更多关于早期生命的生理能力和性质的信息。这一建议解决了在轻度还原性热液和氧化表面沉积物或水之间的界面上的地球微生物过程。具体来说，我们将使用分子，化学和同位素方法的组合来确定嗜热和趋化岩石营养细菌和古细菌的流光和生物膜形成群落（SBC）的地理微生物关联，代谢策略，营养和能量需求以及地球化学特征。我们将解决以下问题：1)形成生物膜的水样的物理化学基础是什么？2)它们的主要碳源和碳同化模式是什么？3)在这些系统中共同殖民的绿原藻的身份是什么？4)这些微生物之间是否存在相互依赖关系，如果存在，其基础是什么？5)生物标记可以用来区分嗜热和中温菌群吗？6)这些系统是否会留下可以追溯到过去的分子记录？科学价值：通过这项研究，我们将进一步了解高温下生命的生理基础和嗜热微生物的特征生物特征。特别是，我们将试图辨别在黄石国家公园的sbc中是否存在一种共生关系或仅仅是一种物理上的共生关系。这些生物在热的亚地下热液流体和“冷的”氧化大气的界面上占据一个特殊的生态位。为了增加对在这个界面上运行的微生物和生物地球化学过程的理解，以及用于获取能量和营养的策略，我们的提议与生物地球科学计划的目标和目标是紧密一致的。在结合先进的地球化学和微生物的方法,我们通常也会改善研究方法和研究技术geomicrobial流程。更广泛的影响：该提案侧重于教学和培训，并将支持麻省理工学院新博士后研究员和研究生的培训，并将为对生物地球科学感兴趣的本科生提供无与伦比的研究机会，包括在三个机构的实地和实验室中进行重要的合作互动。为大学本科生提供有意义和积极的多学科科学研究经验，对培养下一代研究人员和教育工作者至关重要。由于我们的研究重点是美国游客最多的国家公园之一，因此我们的研究结果将有更多的机会向公众传播。我们将直接与公园管理局合作开发教育材料，包括科学合理地处理与“生命的起源”和“生命的极限”概念有关的基础研究的哲学和实践方面。

EAR-0525453/EAR-0525561/EAR-0525500One of the most profound discoveries emanating from molecular phylogenetic studies is that the "universal tree of life" is exclusively populated in its deepest branches by thermophiles. Two opposing theories about why this might be are: Life first arose in a hydrothermal environment, possibly in the deep subsurface.Thermophiles preferentially survived the "late heavy bombardment" of the Hadean Earth. Since no sedimentary record survives from this period, it is not possible to address these theories directly through geology. Instead, we must look to modern geomicrobial processes to better understand controls on, and modes of, thermophilic life. Armed with this understanding, geological records may eventually yield more information on the physiological capabilities and nature of early life.This proposal addresses geomicrobial processes at interfaces between mildly reducing hydrothermal fluids and oxidizing surface sediments or waters. Specifically, we will use a combination of molecular, chemical, and isotopic methods to identify the geomicrobial associations, metabolic strategies, nutrient, and energy requirements and geochemical signatures of streamer and biofilm-forming communities (SBC) of thermophilic and chemolithotrophic Bacteria and Archaea.We will address the following questions:1) What is the physiochemical basis for the occurrence of biofilm-forming Aquificales? 2) What is their primary carbon source and mode of carbon assimilation?3) What are the identities of the Crenarchaeota that appear to co-colonize these systems?4) Is there a co-dependence of these microbes and, if so, what is its basis?5) Can biosignatures be used to distinguish thermophilic and mesophilic communities?6) Might these systems leave a molecular record that could be traced back in time?Scientific Merit: Through this research, we will learn more about the physiological basis for life at high temperatures and the characteristic biosignatures of thermophilic microbes. In particular, we will seek to discern if there is a symbiosis or simply a physical co-habitation of thermophilic Aquificales and Crenarchaea in the SBCs of Yellowstone National Park. These organisms occupy a special niche at the interface of hot, sub-subsurface hydrothermal fluids and a "cold" and oxidizing atmosphere. In seeking to increase understanding of microbes and biogeochemical processes operating at this interface and the strategies used to derive energy and nutrients, our proposal is firmly aligned with the aims and objectives of the Biogeosciences Program. In combining cutting-edge geochemical and microbiological approaches, we will also be generally improving methods and research techniques for the study of geomicrobial processes. Broader Impacts: This proposal focuses on teaching and training and will support the training of a new postdoctoral investigator and graduate student at MIT and will provide unparalleled research opportunities for undergraduates interested in the biogeosciences, including significant collaborative interactions in the field and laboratory at three institutions. Providing meaningful and positive research experiences in multidisciplinary science to college undergraduates is critical to fostering the next generation of researchers and educators. Because the focal point of our research is one of the US's most visited national parks, there will be enhanced opportunities for public dissemination of our results. We will work directly with the Park Service to develop educational materials, including scientifically sound treatment of the philosophical and practical aspects of fundamental research pertaining to "origins of life" and "limits of life" concepts.