Collaborative Research: Autotrophic carbon fixation at a shallow-water hydrothermal system: Constraining microbial activity, isotopic and geochemical regimes

合作研究：浅水热液系统的自养碳固定：限制微生物活动、同位素和地球化学状况

• 批准号: 1124141
• 负责人: Costantino Vetriani
• 金额: $ 19.67万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1124141&HistoricalAwards=false
• 关键词: Collaborative; Research; Autotrophic; carbon; fixation

Currently, there is only limited information on the identity and activity of the microorganisms carrying out CO2-fixation in situ, despite the fact that these organisms form the basis of their respective ecosystems. Representatives that are able to grow autotrophically are known to exist in almost all major groups of prokaryotes, and these organisms play essential roles in ecosystems by providing a continuous supply of organic carbon for heterotrophs. Microorganisms present in extreme environments utilize CO2- fixation pathways other than the Calvin-Benson-Bassham (CBB) cycle. At present, five alternative autotrophic CO2 fixation pathways are known. Different carbon fixation pathways result in distinct isotopic signatures of the produced biomass due to the isotopic discrimination between light (12C) and heavy (13C) carbon by the carboxylating enzymes. Thus, inferences about the carbon fixation pathway predominantly utilized by the microbial community can also be made based on the stable carbon isotopic composition of the organic matter, in extant systems as well as in the geological record. However, at present little is known about the systematics and extents of fractionation during carbon fixation by prokaryotic organisms, and to our knowledge no studies exist that have systematically studied the relationship between the operation of different carbon fixation pathways and how this is reflected in the stable carbon isotopic composition in a natural system. This is a 2-year interdisciplinary, international research program that employs a powerful combination of cutting-edge research tools aiming to improve our understanding of autotrophic carbon fixation and its chemical and isotopic signature along environmental gradients in a natural hydrothermal system. The following hypotheses are addressed: 1. The diversity of microorganisms present along a thermal and redox gradient, and rates of CO2 fixation, will reflect adaptation to in situ temperatures and geochemical conditions 2. Microorganisms utilizing the CBB cycle for autotrophic CO2-fixation will represent a smaller percentage of the chemolithoautotrophic community at higher temperatures, where microorganisms utilizing alternative CO2-fixation pathways dominate 3. Isotopic values of biomass and specific biomarker molecules will vary along a thermal and redox gradient from zones characterized by a higher hydrothermal fluid flux and thus higher temperatures to the surrounding, cooler areas, corresponding to the physiology of the microorganisms utilizing different pathways for carbon fixationThe PIs will use a multidisciplinary approach to delineate the relative contribution of the different carbon fixation pathways along an environmental gradient by combining metagenomic analyses coupled with: 1) an assessment of the frequency and the expression of specific key genes involved in carbon fixation, and 2) with the measurement of carbon fixation rates. These data will be integrated with the determination of stable C isotopic composition of biomass, DIC, and specific hydrocarbons/lipids. Due to its easy accessibility, well-established environmental gradients, and extensive background information, the shallow-water vents off Milos (Greece) will be used as a natural laboratory to perform these studies. Intellectual Merit. The data generated in this study will allow constraints on the relationship between autotrophic carbon fixation and the resulting isotopic signatures of biomass and specific biomarker molecules (e.g. CH4, C2+ alkanes, lipids) in a natural system.. This has implications for assessing the importance of carbon fixation in extant ecosystems, and it will also provide a tool to improve the interpretation of isotopic values in the geological record.Broader Impacts. This is an interdisciplinary and collaborative effort between US and foreign institutions, creating unique opportunities for networking and to foster international collaborations. This will also benefit the involved students (1 graduate, several undergraduates) and a postdoc. The PIs have been involved in several educational and public outreach activities over the years that have reached literally millions of individuals. Finally, the project fits with the focus of a number of multi-disciplinary and international initiatives, in which PIs are active members (e.g. SCOR working group on Hydrothermal energy and the ocean carbon cycle;and Deep Carbon Observatory at CIW).

目前，尽管这些生物体构成了各自生态系统的基础，但有关原位固定二氧化碳的微生物的身份和活性的信息仍然有限。已知能够自养生长的代表几乎存在于原核生物的所有主要类群中，并且这些生物通过为异养生物提供持续的有机碳供应而在生态系统中发挥着重要作用。 极端环境中的微生物利用卡尔文-本森-巴沙姆 (CBB) 循环以外的二氧化碳固定途径。目前，已知有五种替代的自养二氧化碳固定途径。 由于羧化酶对轻碳 (12C) 和重碳 (13C) 的同位素区分，不同的碳固定途径导致所产生的生物质具有不同的同位素特征。因此，关于微生物群落主要利用的碳固定途径的推论也可以基于现有系统以及地质记录中有机物的稳定碳同位素组成。 然而，目前对原核生物固碳过程中分馏的系统性和程度知之甚少，据我们所知，还没有研究系统地研究不同碳固定途径的运行之间的关系以及这如何反映在稳定的碳固定过程中。自然系统中的碳同位素组成。 这是一个为期两年的跨学科国际研究项目，采用了尖端研究工具的强大组合，旨在提高我们对自然热液系统中自养碳固定及其沿环境梯度的化学和同位素特征的理解。提出以下假设： 1. 沿热梯度和氧化还原梯度存在的微生物多样性以及 CO2 固定速率将反映对原位温度和地球化学条件的适应 2. 利用 CBB 循环进行自养 CO2 固定的微生物将代表在较高温度下，化能自养群落的比例较小，其中利用替代 CO2 固定途径的微生物占主导地位 3. 生物量和特定生物标记分子的同位素值将随着温度的变化而变化热液和氧化还原梯度从以较高热液通量为特征的区域到周围较冷的区域，对应于利用不同途径进行碳固定的微生物的生理学。PI将使用多学科方法来描述通过将宏基因组分析与以下方法相结合，沿着环境梯度研究不同的碳固定途径：1）评估参与碳固定的特定关键基因的频率和表达，2）测量碳固定率。 这些数据将与生物质、DIC 和特定碳氢化合物/脂质的稳定 C 同位素组成的测定相结合。 由于其易于到达、完善的环境梯度和广泛的背景信息，米洛斯岛（希腊）的浅水喷口将被用作进行这些研究的天然实验室。 智力优点。本研究生成的数据将限制自然系统中自养碳固定与生物质和特定生物标记分子（例如 CH4、C2+ 烷烃、脂质）的同位素特征之间的关系。这对于评估自然系统中的重要性具有影响。现有生态系统的碳固定，它还将提供一种工具来改进地质记录中同位素值的解释。更广泛的影响。这是美国和外国机构之间的跨学科合作努力，为建立联系和促进国际合作创造了独特的机会。这也将使参与的学生（一名研究生，几名本科生）和一名博士后受益。多年来，PI 参与了多项教育和公共宣传活动，影响了数百万人。最后，该项目符合许多多学科和国际倡议的重点，其中 PI 是积极成员（例如 SCOR 水热能和海洋碳循环工作组；以及 CIW 深碳观测站）。