EAGER: Collaborative Research: Manganese Phototrophy in Cyanobacteria

大约23亿年前氧气的出现可以说是地球历史上最重要的事件。大气中氧气的增加导致了我们今天所知的生命，包括呼吸氧气的生物和多细胞生命，如植物和动物。这一事件主要与蓝藻光合作用产生氧气（O2）的演变有关。光系统II（PSII）是利用光能从水中去除电子并产生O2的催化剂。PSII产生O2的进化途径尚不确定。基于PSII的地质记录和生物化学研究的一种假设是，前体光系统能够从过渡金属锰而不是水获得电子。拟议的工作使用现代蓝藻和PSII来测试这一假设，它们可能仍然能够进行这种反应。这项工作将帮助科学家了解这一重要过程的演变：O2的产生。它还将影响对我们星球上现代锰循环的理解，这会影响环境中许多污染物的命运。在这个跨学科的研究项目从地球生物学计划在研究密集型大学和生物科学计划在一个不同的区域西班牙裔服务主要是本科院校培训的学生将参加共同的小组和专业会议，并发展跨学科的导师-学员关系。调查结果也将被纳入K-12和两所大学的演讲和课程。该项目涉及的假设，“缺失环节”的光合水氧化的光系统II（PSII）的进化是光合Mn（II）的氧化，并检查锰的光合作用在蓝藻来检验这一假设。高价锰物种构成环境中强氧化剂的关键池，参与碳和金属的循环。这项工作将增加现代生物锰氧化的理解和高价锰在自然界中的潜在来源，通过检查细菌锰氧化在锰光养。将使用遗传上易处理的蓝细菌集胞藻属PCC 6803的全细胞和光合作用受损的该生物体的突变体来评价光营养Mn氧化并将其与生长联系起来。Mn氧化光养的化学计量和机制将使用来自这些菌株的纯化PSII来确定。这些研究有可能为我们理解产氧光合作用的演变提供新的见解。更广泛的影响涉及一个研究密集型，主要是本科院校，也是少数民族服务之间的研究合作。这两个机构的学生将相互交流，研究成果将被纳入本科和K-12水平的演讲和课程中。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

The rise of oxygen approximately 2.3 billion years ago was arguably the most significant event in Earth's history. The rise of atmospheric oxygen led to life as we know it today, including organisms that breath oxygen and multicellular life such as plants and animals. This event is principally related to the evolution of oxygen (O2) producing photosynthesis by Cyanobacteria. Photosystem II (PSII) is the catalyst that uses light energy to remove electrons from water and produce O2. The evolutionary route of PSII to produce O2 is uncertain. One hypothesis, based on both the geological record and biochemical studies of PSII, is a precursor photosystem was able to obtain electrons from the transition metal manganese, instead of water. The proposed work tests this hypothesis using modern Cyanobacteria and PSII, which may still be able to perform this reaction. The work will help scientists understand the evolution of this important process: the production of O2. It will also impact understanding of modern manganese cycling on our planet, which affects the fate of many pollutants in the environment. Students trained in this interdisciplinary research project from both a geobiology program at a research intensive university and a biological science program at a diverse regional Hispanic-serving primarily undergraduate institution will attend common group and professional meetings and develop mentor-mentee relationships across disciplines. Findings will also be integrated into presentations and coursework at K-12 and the two universities. This project concerns the hypothesis that the "missing link" in the evolution of photosynthetic water-oxidation by Photosystem II (PSII) was phototrophic Mn(II) oxidation, and examines Mn phototrophy in Cyanobacteria to test this hypothesis. High-valent manganese species comprise a critical pool of strong oxidants in the environment, involved in the cycling of both carbon and metals. This work will add to the understanding of modern biological Mn oxidation and the potential sources of high-valent Mn in nature by examining bacterial Mn oxidation in Mn phototrophy. Phototrophic Mn oxidation will be evaluated and linked to growth using whole cells of the genetically tractable Cyanobacterium, Synechocystis sp. PCC 6803, and a mutant of this organism impaired in photosynthesis. The stoichiometry and mechanism of Mn-oxidizing phototrophy will be determined using purified PSIIs from these strains. These studies have the potential to provide new insight into our understanding of the evolution of oxygenic photosynthesis. The broader impacts concern a research collaboration between a research intensive and primarily undergraduate institution that is also minority serving. Students from the two institutions will interact with each other and the research results will be incorporated into presentations and courses at the undergraduate and K-12 level.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.