Collaborative Research: Were Protists the Beginning of the End for Stromatolites?

合作研究：原生生物是叠层石终结的开始吗？

• 批准号: 0926372
• 负责人: Roger Summons
• 金额: $ 27.1万
• 依托单位: Massachusetts Institute of Technology
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2013-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0926372&HistoricalAwards=false
• 关键词: Collaborative; Research; Were; Protists; Beginning

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Microbial mats are conspicuous components of many benthic marine and aquatic settings. A subset of these microbial mats binds sediments to form potentially fossilizable structures, often called stromatolites or microbialites. While much is known about microbialite autotrophs, little is known about their heterotrophic eukaryotes. The lack of understanding is surprising given that stromatolites have an extensive geologic record spanning most of Earth's history. Stromatolites are layered sedimentary structures formed by a combination of microbial activities, abiotic carbonate precipitation, and sedimentary processes. Details of stromatolite formation and preservation are poorly understood, and a drastic decline in stromatolite occurrence and diversity in the late Precambrian has long been a conundrum. A popular hypothesis to explain this decline at ~1 billion years ago is that eukaryotic organisms evolved to become predators on stromatolites. To date, the most commonly proposed predatory culprit is an unidentified metazoan, although evidence of such an organism is lacking from the fossil record. Protists, most of which are not expected to leave an obvious fossil record, are additional possible stromatolitic predators, but they have been largely ignored in this context. The hypotheses of this project are: (1) Heterotrophic protist activity caused the textural change from stromatolites (layered sediment fabric) to thrombolites (clotted sediment fabric) and (2) Heterotrophic protists caused the decimation of Neoproterozoic stromatolites. Since it is impossible to recreate the Neoproterozoic, studies of modern analogs serve to indirectly test these hypotheses. The overall goal of this project is to describe the eukaryotic communities associated with modern stromatolites and thrombolites from the Bahamas and Australia, compare the communities from the two sites, and to relate the communities to stromatolitic / thrombolitic sediment fabric and biomarker signatures. The overall goal will be achieved by addressing the following specific aims: (1) Identify, via morphologic and molecular approaches, the eukaryotic community of modern stromatolites and thrombolites; (2) Analyze modern and fossil stromatolites and thrombolites for their eukaryotic lipid biomarkers using solvent extraction, chromatographic and mass spectrometric methods; (3) Using the Fluorescently Labeled Embedded Core (FLEC) method, document the sub-millimeter distributions of the heterotrophic eukaryotic community inhabiting modern stromatolites and thrombolites in conjunction with fine-scale sediment fabric; (4) Using solvent extraction, chromatographic and mass spectrometric methods, analyze cultures of allogromiid foraminifers to survey for lipid biomarkers unique to them; (5) After incubation of modern stromatolites with heterotrophic protists, use FLEC methodology to determine how their activity affects sediment fabric and conduct preliminary comparisons of these modern fabrics to those of stromatolite fossils. Intellectual Merit: The oldest fossil stromatolites are 3.4 billion years old and are the most visible manifestations of pervasive microbial life on the early Earth. The changes in stromatolite abundance and morphology document complex interplays between biological and geological processes. This project addresses multiple aspects of stromatolite genesis and pre-fossilization alteration but at its core, focuses on one of the greatest geological enigmas: the possible connection between stromatolite decline and the rise of complex life. Broader Impacts: Because any undergraduate introductory historical geology class (and some middle and high school Earth Science classes) introduces stromatolites as the first highly visible evidence of life on Earth, the results of this project would be interesting to a wide audience. This multidisciplinary project involving benthic ecology, molecular biology, sedimentology, and organic geochemistry includes education opportunities from high school to graduate students and teachers. The project would support a WHOI-MIT Joint Program student for half of his/her PhD studies and an MIT student for half of his/her PhD studies. Additionally, undergraduate students from MIT, the University of Connecticut, and University of Miami will actively participate in some of our field collections and laboratory analyses.

该奖项是根据2009年的《美国回收与再投资法》（公共法第111-5号）资助的。MicrobialMats是许多底栖海洋和水生环境的明显组成部分。 这些微生物垫的一个子集结合了沉积物，形成了潜在的化石结构，通常称为基质石或微生物。虽然对微生物自养生知之甚少，但对它们的异核真核生物知之甚少。缺乏理解令人惊讶的是，层状石具有广泛的地质记录，涵盖了地球大部分历史。基质石是由微生物活性，非生物碳酸盐沉淀和沉积过程组合形成的分层沉积结构。基质石的形成和保存的细节知之甚少，在晚期前寒武纪的质体发生和多样性的大幅下降长期以来一直是一个难题。一个流行的假设解释了大约10亿年前的这种下降的是，真核生物的成长为基质石上的捕食者。迄今为止，最常见的掠夺性罪魁祸首是一个身份不明的后生动物，尽管化石记录中缺乏这种生物体的证据。原生生物（不期望留下明显的化石记录）是额外的基质捕食者，但在这种情况下，它们在很大程度上被忽略了。该项目的假设是：（1）异养原则的活性导致从基质岩（分层沉积物织物）到血栓形成物（凝结的沉积物织物）和（2）异养原则导致Neoperoroterocic atromatolites的分解。由于不可能重现新元古代，因此对现代类似物的研究可间接检验这些假设。该项目的总体目的是描述与来自巴哈马和澳大利亚的现代基质石和血栓形成的真核群落，比较两个地点的社区，并将社区与基质 /血栓形成型沉积物和生物标志物签名相关联。总体目标将通过解决以下特定目的来实现：（1）通过形态学和分子方法确定现代基质石和血栓形成的真核群落； （2）使用溶剂提取，色谱和质谱方法分析现代和化石层状岩和血栓形成的真核脂质生物标志物； （3）使用荧光标记的嵌入式核心（FLEC）方法，记录了居住在现代基质石和血小板的异营养真核群落的亚毫米分布，并与细尺度的沉积物结合在一起； （4）使用溶剂提取，色谱和质谱方法分析同种异体孔的培养物，以调查其独特的脂质生物标志物； （5）在现代基质岩与异养生物孵育后，使用FLEC方法来确定其活性如何影响沉积物织物并进行这些现代织物与质膜化石的初步比较。 知识分子的优点：最古老的化石质体层已有34亿年的历史，是地球早期普遍存在的微生物生命中最明显的表现。基质石丰度和形态的变化文献了生物学和地质过程之间的复杂相互作用。该项目介绍了基质石起源和化石前改变的多个方面，但其核心侧重于最大的地质谜团之一：基质石的衰落与复杂寿命的兴起之间可能的联系。 更广泛的影响：由于任何本科入门历史地质班（以及一些中学地球科学课程）都将基质石作为地球上生命的第一个高度可见的证据，因此该项目的结果对广泛的受众来说都是有趣的。这个涉及底栖生态，分子生物学，沉积学和有机地球化学的多学科项目包括高中到研究生和教师的教育机会。该项目将支持WHOI-MIT联合计划学生的一半博士学位，并为他/她的博士学位学习的一半学生提供支持。此外，来自麻省理工学院，康涅狄格大学和迈阿密大学的本科生将积极参与我们的一些现场收集和实验室分析。