Oxygen production in a model Proterozoic environment

理解地球和生命的共同演化是现代地球科学中最令人兴奋的挑战之一。这个项目的重点是发现生物学如何在决定地球大气何时变得富氧以及以多快的速度变得富氧方面发挥了作用。研究岩石的地质学家收集的信息表明，蓝藻产生的氧气大约在25亿年前开始在地球大气层中积累，随后氧的上升到今天地球大气中的高得多的氧气水平有了很长(10亿年)的延迟。大气中氧气的这种延迟上升代表着我们对地球上古老的生物地球化学循环以及整个行星演化的理解上的一个重要缺口。在有产氧蓝藻存在的情况下，可以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生物地球化学来揭示，特别是那些与地球历史上低氧时期可能是“正常”的环境具有重要的化学和生物相似性的环境。该项目的动机是对小盐泉的初步研究结果，小盐泉是一个喀斯特天坑湖，阳光充足的区域处于氧化和硫化(缺氧)条件之间，以及快速生长的顶峰形成的蓝藻垫子。主要目标是了解在这个系统中是什么控制着氧气生产和消耗的平衡，特别是改变氧气生产和碳固定平衡的阈值。研究人员将使用氧气和硫化物微型传感器(有时由科学潜水员操作)，一个特殊建造的垫子操作室，最近在垫子中获得主要蓝藻的纯培养，以及基于DNA的方法来剖析生态系统的行为和组成物质的主要蓝藻。微传感器实验的重要材料支持将通过与马克斯·普朗克海洋微生物研究所的合作免费提供，后者与研究人员有着长期的合作。项目资金用于指导一名博士生、一名本科生和一名女性博士后学者，并加强美国和德国研究人员之间新生的合作网络。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、黏液、极端微生物和早期生命的高度兴趣，拟议的项目提供了极好的推广机会。图像和微生物培养将用于每年2000名K-12学生和家长以及150名三年级学生参加实践科学课程的年度外展和教育活动。

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.