Oxygen production in a model Proterozoic environment

理解地球与生命的共同进化是现代地球科学中最令人兴奋的挑战之一。该项目的重点是发现生物学如何在确定地球大气层何时以及以多快的速度变得富含氧气方面发挥作用。地质学家研究岩石收集的信息表明，蓝藻产生的氧气大约在25亿年前开始在地球大气中积累，随后氧气的上升延迟了很长时间（10亿年），直到今天地球大气中的氧气水平更高。大气中氧气的延迟上升代表了我们对地球上古代地球化学循环以及行星演化的理解中的一个重要空白。在产生氧气的蓝细菌存在下，可能稳定低氧早期地球的机制很难想象，但可以通过研究当今缺氧环境的地球化学来揭示，特别是那些与地球历史上低氧时期可能“正常”的环境具有重要化学和生物相似性的环境。该项目的动机是来自小盐泉的初步研究结果，小盐泉是一个喀斯特天坑湖，阳光照射区位于好氧和硫化物（缺氧）条件之间，并有一个快速生长的形成尖峰的蓝藻垫。主要目标是了解是什么控制着这个系统中氧的产生和消耗的平衡，特别是改变氧的产生和碳固定的平衡的阈值。研究人员将使用氧气和硫化物微传感器（有时由科学潜水员操作），一个专门建造的垫子操作室，最近获得了垫子中主要蓝藻的纯培养物，DNA-的方法来解剖生态系统的行为和主要的蓝藻组成的垫。重要的材料支持的微传感器实验将提供免费通过与马克斯普朗克合作海洋微生物学研究所，该研究所与研究人员有着长期的合作关系。项目资金用于指导一名博士。学生，一名本科生和一名女博士后学者，并加强了美国和德国研究人员之间的合作网络。调查员在培训各级成功的女学者方面有着良好的记录。由于公众对水下探索、洞穴、粘液、极端微生物和早期生命的高度兴趣，拟议的项目提供了绝佳的外联机会。图像和微生物培养物将用于每年的宣传和教育活动，每年有2000名K-12学生和家长以及150名三年级学生参加科学实践活动。

Understanding the co-evolution Earth and life is one of the most exciting challenges in modern geoscience. This project is focused on discovering how biology may have played a role in determining when and how fast the Earth's atmosphere became oxygen-rich. Information gathered by geologists studying rocks shows that whereas oxygen produced by cyanobacteria first began to accumulate in the Earth's atmophere about 2.5 billion years ago, there was subsequently a long ( 1 billion years) delay in the rise of oxygen to the much higher levels of oxygen present in the Earth's atmosphere today. This delayed rise of oxygen in the atmosphere represents an important gap in our understanding of ancient biogeochemical cycling on Earth as well as planetary evolution in general. Mechanisms that could have stabilized the low-oxygen early Earth in the presence of oxygen producing cyanobacteria are difficult to envision, but could be revealed by investigating the biogeochemistry of today's oxygen-poor environments, especially those that have important chemical and biological similarities with environments likely to have been "normal" during the low-oxygen period in Earth's history. The project is motivated by results from initial studies of Little Salt Spring, a karst sinkhole lake with a sunlit zone poised between oxic and sulfidic (anoxic) conditions and a fast-growing pinnacle-forming cyanobacterial mat. The primary objectives are to understand what controls the balance of oxygen production and consumption in this system, especially thresholds that change the balance of oxygen production and carbon fixation. The investigator will use oxygen and sulfide microsensors (sometimes operated by science divers), a specially constructed mat manipulation chamber, recently obtained pure cultures of the main cyanobacteria in the mat, and DNA-based approaches to dissect the behavior of the ecosystem and the main cyanobacteria making up the mat.Significant material support for the microsensor experiments will be provided free of cost via a collaboration with the Max Planck Institue for Marine Microbiology, who have a long-standing collaboration with investigator. Project funds provide for the mentoring of a Ph.D. student, an undergraduate student, and a female postdoctoral scholar, and strengthen a nascent network of collaborations among researchers in the USA and Germany. The investigator has an excellent track record of training successful female scholars at all training levels. The proposed project provides outstanding opportunities for outreach due to high public interest in underwater exploration, caves, slime, extreme microbes, and early life. Images and microbial cultures will be utilized in annual outreach and education events reaching 2000 K-12 students and parents each year as well as 150 third grade students who spend the day in hands-on science sessions.