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

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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.