CAREER: Uncovering the origins and biological purpose of the orphaned branched GDGT temperature biomarker

职业：揭示孤支链 GDGT 温度生物标志物的起源和生物学目的

• 批准号: 1945484
• 负责人: Sebastian Kopf
• 金额: $ 53.77万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1945484&HistoricalAwards=false
• 关键词: CAREER; Uncovering; origins; biological; purpose

Understanding Earth’s past is often the key to understanding our planet’s future. Towards this goal, geochemists use many different tools to study Earth’s climate history. Different tools provide different clues that together help solve the puzzle of what happened in the past. A new set of clues first discovered at the turn of the century (~2000) comes from so called branched tetra ether lipids. Lipids are organic molecules that form the boundary between the inside and outside of cells in all known cellular life including animals, plants, and bacteria. Lipids provide important clues about Earth’s history because they are made by living organisms yet can persist in the environment long after the organism dies. Unlike DNA, sugars and enzymes which tend to break down quickly, some lipids can be preserved in rocks for millennia. This helps uncover at what times in the past different organisms were present. Unfortunately, most lipids do not contain much information about the environment the cell that produced them lived in. This is why the newly discovered tetra ether lipids are of such great scientific interest. These lipids occur in different variations that seem to correspond to the temperature and pH of the environment in which they were formed. In theory, this makes it possible to infer the temperature and pH of past environments. These lipids thus pose a great opportunity to help understand Earth’s climate history. However, it is not known which organisms produce these lipids and why they produce them. This makes it difficult to fully assess how reliable the information is that they can provide about Earth’s past. It also makes it difficult to study what else we could learn from them about Earth’s history. So far it is clear that the organisms that produce them are widespread. These lipids have been found almost everywhere in nature since their discovery 20 years ago. They are twice the size of most plant and animal lipids and are built with stronger chemical bonds. They are especially common in soils and some aspects of their structure suggest they are most likely produced by bacteria. Several types of soil bacteria have been tested in the past decade but no clear source has emerged. The goal of this project is thus to find and study the source of these branched tetra ether lipids by systematically investigating two important reasons they might have gone undetected. First, microbes often produce large organic molecules only when they are needed. Soil bacteria tested in the past might have been prevented from producing these lipids because standard laboratory conditions do not reflect common soil environments. This project will work with a range of soil bacteria in conditions that mimic soil habitats to test this possibility. Second, the bacteria that produce these lipids in the environment might not yet be cultured. To address this possibility, this project will develop a new Course-based Undergraduate Research Experience (CURE). The focus of this CURE will be student-driven isolation and testing of new soil bacteria for these lipids from sites all around Colorado. This CURE will be taught every year at CU Boulder and nearby Red Rocks Community College. In addition, this project will evaluate how undergraduate research experiences impact students’ views on science and interest in science & engineering career paths.Branched tetraether (brGDGT) lipids are well-preserved, vastly distributed molecular biomarkers with tremendous potential for paleoclimate reconstruction. First described in 2000, brGDGTs are now recognized to exist in virtually all natural environments and their abundance and structural variations are being applied to topics of broad biogeochemical interest. This includes brGDGT-based paleotemperature records that are increasingly used to address fundamental questions in paleoclimate research. However, this rapid expansion has greatly surpassed our fundamental understanding of what brGDGT-based proxies actually represent and how they might have differed in Earth's geologic past. The root of this problem lies with the fact that brGDGTs remain one of the most puzzling "orphaned" biomarkers today. We know little about their biological origins and next to nothing about their biological function. This implies either that potential source organisms cultured to date have not been exposed to the environmental conditions that trigger brGDGT production, or that key source organisms have not yet been cultured or studied in the lab. This projects aims to address both of these possibilities by integrating research and education to advance our understanding of the origins and biological purpose of brGDGTs. The hypothesis that brGDGT production is environmentally induced will be tested using a range of microorganisms that produce potential brGDGT precursor molecules. In particular, the dependence of brGDGT production upon O2, CO2, nutrient flux, and soil microbial interactions will be investigated. The research team will employ chemically static (chemostat) culturing approaches and evaluate the resulting production of brGDGTs and their biosynthetic precursors. The hypothesis that the source organisms of brGDGTs remain uncultured will be pursued by evaluating the production of a brGDGT precursor in bacteria isolated by undergraduate students in a Course Based Undergraduate Research Experience (CURE) class. This class will be developed with a focus on student-driven research into the isolation and study of novel soil bacteria, their metabolites and lipid products. CURE classes provide more inclusive access to early research experiences which are often transformative to students' science identity by increasing self-efficacy and basic research skills. This can lead to increased retention in STEM fields with particularly positive outcomes for first generation and minority students. The development and implementation of the proposed CURE will expose more than 900 undergraduate STEM students to hands-on, cross-disciplinary scientific research practices, collaboration and discovery.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.

了解地球的过去往往是了解地球未来的关键。为了实现这一目标，地球化学家使用许多不同的工具来研究地球的气候历史。不同的工具提供了不同的线索，这些线索共同帮助解开了过去发生的事情的谜团。在世纪之交（~2000年）首次发现的一组新的线索来自于所谓的支化四醚脂质。脂质是一种有机分子，在所有已知的细胞生命（包括动物、植物和细菌）中形成细胞内外的边界。脂质为了解地球历史提供了重要线索，因为它们是由生物体产生的，但在生物体死亡后仍能在环境中长期存在。不像DNA、糖和酶容易迅速分解，一些脂质可以在岩石中保存数千年。这有助于揭示在过去不同的生物存在的时间。不幸的是，大多数脂质并不包含产生它们的细胞所处环境的太多信息。这就是为什么新发现的四醚脂具有如此巨大的科学兴趣。这些脂质以不同的变化形式出现，似乎与它们形成的环境的温度和pH值相对应。理论上，这使得推断过去环境的温度和pH值成为可能。因此，这些脂质提供了一个很好的机会来帮助了解地球的气候历史。然而，目前尚不清楚哪些生物会产生这些脂质以及它们为什么会产生这些脂质。这使得很难完全评估它们提供的关于地球过去的信息有多可靠。这也使得我们很难从它们身上了解到关于地球历史的其他信息。到目前为止，很明显，产生它们的生物是广泛存在的。这些脂质自20年前被发现以来，在自然界中几乎无处不在。它们的大小是大多数植物和动物脂类的两倍，并且具有更强的化学键。它们在土壤中特别常见，其结构的某些方面表明它们最有可能是由细菌产生的。在过去的十年里，人们对几种土壤细菌进行了测试，但没有发现明确的来源。因此，该项目的目标是通过系统地调查它们可能未被发现的两个重要原因，找到并研究这些支链四醚脂质的来源。首先，微生物通常只在需要的时候才产生大的有机分子。过去测试的土壤细菌可能无法产生这些脂质，因为标准的实验室条件不能反映普通的土壤环境。该项目将在模拟土壤栖息地的条件下对一系列土壤细菌进行研究，以测试这种可能性。其次，在环境中产生这些脂质的细菌可能还没有被培养出来。为了解决这种可能性，该项目将开发一种新的基于课程的本科生研究体验（CURE）。这个CURE的重点将是学生驱动的分离和测试来自科罗拉多州各地的这些脂质的新土壤细菌。这门课程每年都会在科罗拉多大学博尔德分校和附近的红石社区学院教授。此外，本项目将评估本科研究经历如何影响学生对科学的看法和对科学与工程职业道路的兴趣。支化四醚（brGDGT）脂质是一种保存完好、分布广泛的分子生物标志物，具有重建古气候的巨大潜力。brGDGTs于2000年首次被描述，现在被认为存在于几乎所有的自然环境中，它们的丰度和结构变化正被广泛应用于生物地球化学领域。这包括基于brdgg的古温度记录，这些记录越来越多地用于解决古气候研究中的基本问题。然而，这种快速扩张大大超出了我们对基于brdgg的代理实际上代表的内容以及它们在地球地质历史中可能存在的差异的基本理解。这个问题的根源在于，brGDGTs仍然是当今最令人费解的“孤儿”生物标志物之一。我们对它们的生物学起源知之甚少，对它们的生物学功能也几乎一无所知。这意味着，要么迄今为止培养的潜在来源生物尚未暴露于触发brGDGT产生的环境条件下，要么关键来源生物尚未在实验室中培养或研究。该项目旨在通过整合研究和教育来解决这两种可能性，以促进我们对brGDGTs的起源和生物学目的的理解。brGDGT的产生是环境诱导的假设将使用一系列产生潜在brGDGT前体分子的微生物进行测试。特别是，brGDGT生产对O2， CO2，养分通量和土壤微生物相互作用的依赖将被研究。研究小组将采用化学静态（恒化）培养方法，并评估由此产生的brGDGTs及其生物合成前体。在基于课程的本科研究经验（CURE）课程中，通过评估本科生分离的细菌中brGDGT前体的产生，来验证brGDGT源生物未被培养的假设。本课程将侧重于学生对新型土壤细菌及其代谢物和脂质产物的分离和研究。CURE课程提供了更广泛的早期研究经验，通过提高自我效能和基本研究技能，这些经验通常会改变学生的科学身份。这可以提高STEM领域的留用率，对第一代和少数族裔学生产生特别积极的影响。拟议的CURE的开发和实施将使900多名STEM本科生接触到动手，跨学科的科学研究实践，合作和发现。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Oxygen limitation can trigger the production of branched GDGTs in culture

• DOI: 10.7185/geochemlet.2132
• 发表时间: 2021-01-01
• 期刊: GEOCHEMICAL PERSPECTIVES LETTERS
• 影响因子: 4.9
• 作者: Halamka, T. A.;McFarlin, J. M.;Kopf, S. H.
• 通讯作者: Kopf, S. H.

Revised fractional abundances and warm-season temperatures substantially improve brGDGT calibrations in lake sediments

• DOI: 10.5194/bg-18-3579-2021
• 发表时间: 2021-01
• 期刊: Biogeosciences
• 影响因子: 4.9
• 作者: J. Raberg;David J. Harning;S. Crump;G. De Wet;A. Blumm;S. Kopf;Á. Geirsdóttir;G. Miller;J. Sepúlveda