CAREER: An Evolutionary Framework for the Molecular Fossil Record

生物会产生非生物物质无法产生的化合物。这些化合物中的一些被保存在岩石中，为生活在过去的有机体提供了“生物签名”。对这些生物特征的研究对于自然资源勘探、识别污染源、重建地球上生命的历史，甚至在火星上寻找生命迹象都是有价值的。虽然科学家们非常擅长识别岩石中包含的生物特征，但在确定每种化合物是由哪种生物组成的问题上，存在着许多分歧。该项目使用遗传学的最新工具来确定哪些活着的有机体拥有进行各种生物签名所需的基因，以及它们的祖先在过去何时获得了这种能力。该项目的推广部分包括开发课程，培训年轻的地质学家将这些遗传工具用于自己的研究，以及为美国印第安人学者提供指导计划。该项目侧重于斯特烷，这是一种从真核生物细胞膜中发现的甾醇产生的地球化学生物特征。该项目将比较基因组学和分子时钟分析相结合，以确定甾醇生物合成所需的基因何时进化，以及哪些组在地质时期拥有相关基因。这些工具将被用来重新评估最近在斯特烷研究中备受瞩目的研究，包括~5.6亿年前的狄金森化石是否代表早期动物，~6.3亿年前的24-异丙基胆烷是否为第一批海绵提供了生物标志物，以及不寻常的~16亿年前的斯特烷是否来自真核生物或细菌来源。更广泛的影响包括为年轻的地球科学家开设一个计算系统发生学的短期课程，该课程将每年在加州理工大学的国际地质生物学课程上教授。另一个项目是针对加利福尼亚州莱克县周围的美国印第安人社区大学生。通过已建立的关系，我们将招募有前途的学生在加州大学戴维斯分校博德加海洋实验室进行暑期研究和专业化。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。

Living things produce chemical compounds that cannot be produced from non-living matter. Some of these compounds get preserved in rocks and provide “biosignatures” for organisms that lived in the past. The study of these biosignatures is valuable for natural resource exploration, identifying sources of pollution, reconstructing the history of life on Earth, and even when looking for signs of life on Mars. While scientists are very good at identifying the biosignatures contained in rocks, there is a lot of disagreement when it comes to determining what sort of organism made each compound. This project uses the latest tools in genetics to identify what living organisms have the genes necessary to make various biosignatures, and when in the past their ancestors gained that ability. Outreach components of this project involve developing courses to train young geologists to use these genetic tools for their own research, as well as a mentoring program for American Indian scholars.This project focuses on steranes, a geochemical biosignature produced from the sterols found in the cell membranes of eukaryotes. This project combines comparative genomics and molecular clock analyses to determine when the genes required for sterol biosynthesis evolved, and which groups had the relevant genes through geologic time. These tools will be leveraged to reevaluate recent high-profile studies in sterane research, including whether the ~560 million-year-old fossil Dickinsonia represents an early animal, whether ~630 million-year-old 24-isopropylcholestanes provide a biomarker for the first sea sponges, and whether unusual ~1.6 billion-year-old steranes came from eukaryote or bacterial sources. Broader impacts include a short course in computational phylogenetics for young geoscientists, which will be taught annually at Caltech’s International Geobiology Course. An additional program targets American Indian community college students around Lake County, California. Through established connections we will recruit promising students for summer research and professionalization at the UC Davis Bodega Marine Laboratory.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.