Hopanoid Physiology: Implications for Microbial Life on the Early Earth

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Lipid biomarkers preserved in ancient sedimentary rocks provide a key record of early life on Earth. They carry structural and isotopic information directly reflecting the biochemical pathways of their associated organisms. This information can shed light on early evolution and environments and provides one of the few available windows to the composition of ancient ecosystems. Among the most ancestral lipid biomarkers are the hopanes, diagenetic products of bacterial hopanoids. The ability to synthesize hopanoids or similar molecules probably was present in the last common ancestor of Bacteria, and this pathway subsequently was lost from most taxonomic groups. Hopanoids are one of the few biological products that directly record biological activity on the early Earth. This project will take a physiological approach to understanding the evolution and function of hopanoids with the goal to increase our understanding of conditions on early Earth. The PIs will undertake a three-part study: 1) Biosynthesis and cellular setting of hopanoids, 2) Phenotype and physiology, 3) Adaptation to hopanoid modification and implications for evolution of early life.The broader impacts resulting from this project will be realized through mentoring, community outreach, and undergraduate education. PIs Marx and Pearson will mentor postdoctoral fellow Alexander Bradley throughout the project. In turn, Dr. Bradley will mentor an undergraduate student through Harvard's Microbial Sciences Initiative, which makes a strong effort to recruit students from economically and ethnically diverse backgrounds. Through the Microbial Sciences Initiative we will also participate in a series of day-long professional development workshops for K-12 science teachers. The PIs and Dr. Bradley will participate in developing the curriculum and leading laboratory activities to communicate cutting-edge results to teachers from diverse backgrounds. Finally, this project will form the basis for a new module of a project-based research course designed to teach research-skills to undergraduates within the broader theme of microbial evolution.