Collaborative Research: Carbon Monoxide Dynamics in Geothermal Mats and Earth's Early Atmosphere

合作研究：地热垫和地球早期大气中的一氧化碳动力学

• 批准号: 0747412
• 负责人: Albert Colman
• 金额: $ 18.97万
• 依托单位: University of Chicago
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0747412&HistoricalAwards=false
• 关键词: Collaborative; Research; Carbon; Monoxide; Dynamics

Anaerobic carbon monoxide (CO) oxidation was likely a significant mode of metabolism on the early Earth. Hydrothermal settings today may provide a modern analogue for the study of this ancient microbial energy source and its relation to carbon fluxes on the early Earth. CO is a common trace gas in volcanic emissions and associated hot springs. CO is toxic to numerous microbes because of its strong affinity for the active sites of many metalloenzymes. Nevertheless, several hot spring bacteria have been isolated that are capable of chemolithoautotrophic growth via anaerobic oxidation of CO (CO + H2O = CO2 + H2) in cultures supported by headspace CO partial pressures exceeding 1 atm. Uzon Caldera and Geyser Valley on the Kamchatka Peninsula in far eastern Siberia are the source regions for several anaerobic carboxydotrophic species. Curiously, the concentrations of CO in the isolation locales are much lower than those in which these carboxydotrophic microbes thrive when cultured. Furthermore, CO consumption rates observed in the anoxic muds of the hot spring outflow channels are far higher than can be supported by the CO supplied by venting reduced waters. These observations imply that in situ production of CO, presumably by other microbes and resulting in locally high CO concentrations, sustains the thriving carboxydotrophic communities. Before the rise of oxygen in the Paleoproterozoic, outgassing of a small portion of this CO produced in anaerobic mats could have been a significant source of CO to the atmosphere. Intellectual Merit. This study will provide the first detailed field and laboratory examination of CO production and consumption in hot spring sediments. We will target hot springs in Uzon Caldera, Kamchatka, and analogous springs in Devil?s Kitchen, Lassen Volcanic National Park, California. Fine scale chemical gradients in spring sediments will be assessed using scanning voltammetry microelectrodes. CO consumption rates and products will be determined by in situ 14CO tracer incubations. Couplings between CO cycling and various metabolic modes (i.e., sulfate, FeIII, and MnIV reduction as inferred in the field from microelectrode profiles) will be tested using redox-gradient reactors in the lab. Cryosections of sediment mini-cores will be used for DNA extraction to profile microbial communities in these redox gradients. We will also make preliminary assessments of CO exchange with the atmosphere through measuring CO concentrations in vadose zone gases in relation to dissolved concentrations in the underlying saturated zone. As a result, this work will improve our understanding of the role that carboxydotrophy may have played as a standalone metabolism and as a means of mediating CO fluxes to and from the atmosphere on the early Earth. This work will also pioneer the use of fluorescent reporters in genetically engineered thermophiles as an analytical tool for laboratory microcosm experiments. Localized hot spots of CO production are not resolvable using current methods. The carboxydotrophs with recombinant fluorescent reporters will serve as visual indicators of zones with high dissolved CO concentrations, and will demonstrate more broadly the utility of biosensors in geochemistry. Broader Impacts. This proposal provides partial support for one graduate student at University of Chicago and one at U. Maryland Biotechnology Inst., with additional travel and logistical support for a summer undergraduate intern at U. Chicago to participate in both field seasons. This work will extend our existing international collaboration with members of the Kamchatka Institute of Volcanology and Seismology and the Russian Academy of Sciences in Moscow. Finally, the proposed research will be shared with the general public through the extension of a nationally recognized public outreach collaboration on Kamchatka extremophiles with the San Francisco Exploratorium. A web exhibit will be developed in both English and Russian to describe the research approach and major findings from this biogeochemistry study.

厌氧一氧化碳（CO）氧化可能是早期地球上一种重要的代谢模式。今天的热液环境可能为研究这种古老的微生物能源及其与早期地球碳通量的关系提供了一个现代的类似物。CO是火山排放物和相关温泉中常见的微量气体。一氧化碳对许多微生物是有毒的，因为它对许多金属酶的活性位点有很强的亲和力。尽管如此，一些温泉细菌已经被分离出来，它们能够在超过1atm的顶空CO分压支持下通过CO （CO + H2O = CO2 + H2）的厌氧氧化来进行化石自养生长。西伯利亚远东堪察加半岛上的乌宗火山口和间歇泉谷是几种厌氧羧营养物种的发源地。奇怪的是，隔离区CO的浓度远低于这些羧营养微生物在培养时茁壮成长的地方。此外，在温泉流出通道缺氧泥浆中观察到的CO消耗率远远高于排气还原水提供的CO所能支持的速率。这些观察结果表明，就地产生的CO（可能是由其他微生物产生的）并导致局部高浓度的CO，维持了旺盛的羧营养群落。在古元古代氧气上升之前，厌氧垫中产生的一小部分CO的排放可能是大气中CO的重要来源。知识价值。这项研究将首次对温泉沉积物中CO的产生和消耗进行详细的实地和实验室检查。我们的目标是堪察加半岛乌宗火山口的温泉，以及魔鬼？加州拉森火山国家公园的厨房。利用扫描伏安法微电极对春季沉积物中的细尺度化学梯度进行评估。CO消耗率和产品将通过原位14CO示踪剂孵育来确定。CO循环和各种代谢模式之间的耦合（即硫酸盐、FeIII和MnIV还原，根据现场微电极轮廓推断）将在实验室中使用氧化还原梯度反应器进行测试。沉积物微型岩心的冷冻切片将用于DNA提取，以描述这些氧化还原梯度中的微生物群落。我们还将通过测量渗透区气体中的CO浓度与下面饱和区溶解浓度的关系，对与大气的CO交换进行初步评估。因此，这项工作将提高我们对羧营养可能作为一种独立的代谢和作为一种调节早期地球大气中CO通量的手段所起作用的理解。这项工作也将开拓在基因工程嗜热菌中使用荧光报告作为实验室微观实验的分析工具。目前的方法无法解决CO生产的局部热点问题。具有重组荧光报告的羧营养体将作为高溶解CO浓度区域的视觉指示器，并将更广泛地展示生物传感器在地球化学中的应用。更广泛的影响。该提案为芝加哥大学的一名研究生和马里兰大学生物技术研究所的一名研究生提供部分支持，并为芝加哥大学的一名暑期本科生实习生提供额外的旅行和后勤支持，以参加两个实地季节。这项工作将扩大我们与堪察加火山学和地震学研究所以及莫斯科俄罗斯科学院成员之间现有的国际合作。最后，拟议的研究将通过扩展与旧金山探索博物馆在堪察加极端微生物方面的全国公认的公共外展合作，与公众分享。一个英文和俄文的网络展览将描述这项生物地球化学研究的研究方法和主要发现。