CAREER: Crossing over into the geochemical milieu: Using the molecular genomic record to inform the geologic biomarker record

地球在其整个历史上经历了重大的环境变化，这些变化影响了生命及其进化。我们对生命是如何在不断变化的地球上进化的理解，主要是基于对植物和动物化石的研究，这些化石揭示了宏观生物的丰富性和多样性的深刻变化。然而，在动植物出现之前，古代地球是由微生物主导的，没有留下容易识别的结构化石。因此，在地球遥远的过去的背景下研究微生物生命是必要的。其中一种方法是将现代微生物产生的分子与保存在沉积岩中的分子联系起来。这些生物标志物分子的功能是分子化石，可以提供对古代气候事件、大规模灭绝和地球历史上各种进化过渡的重要洞察。然而，对脂质生物标记物的正确解释依赖于对其在现代系统中产生的广泛理解。这个项目将使用分子和生化方法的组合来解决悬而未决的生物标记问题，这些问题已经混淆了对岩石记录中这些分子的解释。这些研究将使我们了解生命在整个地球历史上如何应对戏剧性的生态变化，并可能为现代生物可能如何应对今天的长期大气和气候变化提供洞察。该项目的更广泛影响集中在开发一门以探究为基础的本科实验室课程，将拟议的研究目标纳入课程。分子地质微生物学实验室课程将允许学生体验完整的科学过程-从开发假说到检验这些假说，再到准备一份手稿来传播他们的发现。此外，本课程将让来自不同科学背景的学生了解地球生物学的跨学科性质。这项建议还将为来自不同背景的本科生提供在PI实验室进行研究的机会。该项目将解决三个生物标记物的不确定性，目的是提供实验证据，以允许改进生物标记物的解释。这些措施包括确定在沉积岩中发现的孤儿生物标记物的潜在微生物来源，确定海绵类固醇生物标记物假说的稳健性，以及表征古细菌中古温度代理类脂GDGT的合成。地球的历史标志着大气和气候剧烈波动的时期，这些波动极大地影响了地球的生物圈和地圈。生物标记物脂质可以提供一个了解这些相互作用的窗口，该项目的目标是更好地了解控制脂质生物标记物的分布和保存的过程和来源。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Earth has experienced significant environmental change throughout its history and these changes have impacted life and its evolution. Our understanding of how life has evolved on our changing planet is primarily based on studies of plant and animal fossils that have revealed profound changes in the abundance and diversity of macroscopic organisms. However, prior to the emergence of animal and plant life, the ancient Earth was dominated by microbial organisms that did not leave easily identifiable structural fossils. Thus, alternative approaches are necessary to study microbial life in the context of Earth's distant past. One such approach is to link molecules produced by modern day microbes to molecules preserved in sedimentary rocks. These biomarker molecules function as molecular fossils that can provide significant insight into ancient climatic events, mass extinctions, and various evolutionary transitions throughout Earth's history. However, the proper interpretation of lipid biomarkers is dependent on a broad understanding of their production in modern systems today. This project will use a combination of molecular and biochemical approaches to address outstanding biomarker questions that have confounded the interpretation of these molecules in the rock record. These studies will inform our understanding of how life has responded to dramatic ecological change throughout Earth's history and could provide insight into how modern organisms may respond to long-term atmospheric and climate changes today. The broader impacts of this project focus on developing an inquiry-based undergraduate laboratory course that incorporates the proposed research objectives into the curriculum. The Molecular Geomicrobiology Laboratory course will allow students to experience the full scientific process - from developing hypotheses to testing those hypotheses to preparing a manuscript to disseminate their findings. In addition, this course will expose students from diverse scientific backgrounds to the interdisciplinary nature of geobiology. This proposal will also provide undergraduate student from diverse backgrounds research opportunities in the laboratory of the PI.This project will address three biomarker uncertainties with the goal of providing experimental evidence to allow for improved biomarker interpretations. These include identifying potential microbial sources for orphan biomarkers detected in sedimentary rocks, determining the robustness of the sponge sterol biomarker hypothesis, and characterizing the synthesis of the paleotemperature proxy lipids, GDGTs, in archaea. Earth's history is marked with periods of dramatic atmospheric and climate fluctuations that greatly impacted the Earth's biosphere and geosphere. Biomarker lipids can provide a window into those interactions and it is the goal of this project to generate a better understanding of the processes and sources that control the distribution and preservation of lipid biomarkers.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.