Collaborative Research: Biochemical, Genetic, Metabolic and Isotopic Constraints on an Ancient Thiobiosphere

磷和氧之间的化学键在构建DNA和RNA以及为现代细胞提供能量方面非常重要。然而，尚不清楚最初的生命形式是否具有相同的化学性质，特别是早期生命可能以硫而不是磷为燃料。这个项目将从现代生活中硫基化学的痕迹往回追溯，重建硫氧键在早期生态系统中的作用。用这种方法做出的预测将与25亿年前岩石中的碳和硫同位素记录进行比较。我们将利用天体生物学社交媒体平台（SAGANet）与公众就这个项目和地球上生命进化的其他研究进行对话。磷酸酯，如核苷酸三磷酸、二磷酸和焦磷酸，是所有活细胞能量代谢的核心成分。然而，目前尚不清楚它们在生命起源或第一批细胞中是否也具有同样重要的作用，或者是否有另一种化学物质在那里起着同样的作用。从地球化学、分子进化和系统生物学的角度考虑，硫酯——基于硫而不是磷的高能键——可能在地球上的第一次代谢中提供了能量。该项目将对硫酯利用的自然历史进行广泛而详细的了解，从当代代谢中回溯重建古代生物化学，同时研究可以将硫酯形成和降解结合起来的前生物化学。这两条研究路线将使研究小组能够推断出假定的早期硫生物圈中重要代谢途径的碳和硫同位素特征，并测试这些特征是否保存在25亿年前的地质记录中。该项目的结果应具有广泛的兴趣，该项目将通过期刊出版物以及已建立的天体生物学社交媒体平台（SAGANet）与科学界和公众进行接触。选择一些传统上在科学领域代表性不足的高中服务社区，将通过由SAGANet研究生导师领导的学期项目，并由该项目的研究人员促进。

Chemical bonds between phosphorus and oxygen are important in building DNA and RNA, and also in supplying modern cells with energy. It is not known, however, whether the first life forms had the same chemistry, and early life in particular may have run on sulfur instead of phosphorus. This project will work backwards from the traces of this sulfur-based chemistry in modern life to reconstruct the role of sulfur-oxygen bonds in early ecosystems. Predictions made from this approach will be compared to the carbon and sulfur isotope record in 2.5 billion year old rocks. We will use the astrobiology social media platform (SAGANet) for the conversations with public about this project and other studies of evolution of life on Earth. Phosphate esters, such as nucleotide triphosphates, diphosphates, and pyrophosphate, are the central component of energy metabolism in all living cells. It is not known, however, whether they were of similar paramount importance at the origin of life or in the first cells, or whether another kind of chemistry was playing the same role there. Considerations from geochemistry, molecular evolution, and systems biology imply that thioesters - high-energy bonds based on sulfur instead of phosphorus - may have supplied energy in the first metabolisms on Earth. This project will develop a broad and detailed understanding of the natural history of thioester utilization, working backwards to reconstruct ancient biochemistry from contemporary metabolism, and simultaneously examining pre-biological chemistries that can couple thioester formation and degradation. These two lines of study will allow the research team to infer the carbon and sulfur isotopic signatures of important metabolic pathways in a putative early thiobiosphere, and test whether these signatures are preserved in the 2.5 billion year old geological record. The results of this project should be of broad interest, and the project will engage with the scientific community and the public through journal publications as well as an established astrobiology social media platform (SAGANet). Select high school serving communities traditionally underrepresented in science will be reached through semester-long programs led by SAGANet graduate student mentors and facilitated by the investigators of this project.