EAGER: Collaborative Research: Manganese Phototrophy in Cyanobacteria

大约23亿年前氧气的上升可以说是地球历史上最重大的事件。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产生光合作用的氧气(O2)的演化有关。光系统II(PSII)是一种催化剂，它利用光能从水中去除电子并产生氧气。PSII产生O2的进化路线尚不确定。一种假设是，基于PSII的地质记录和生物化学研究，前驱光系统能够从过渡金属锰而不是水中获得电子。这项拟议的工作使用现代蓝藻和PSII来验证这一假说，它们可能仍然能够执行这一反应。这项工作将帮助科学家了解这一重要过程的演变：氧气的产生。它还将影响对我们星球上现代锰循环的理解，这影响到环境中许多污染物的命运。接受这一跨学科研究项目培训的学生，既有研究密集型大学的地球生物学项目，也有地区多元化的拉美裔本科生为主的本科院校的生物科学项目，他们将参加共同的小组和专业会议，并建立跨学科的导师-学员关系。调查结果还将被整合到K-12和两所大学的报告和课程中。本项目涉及光系统II(PSII)光合作用水氧化进化中的“缺失环节”是光养Mn(II)氧化这一假说，并通过研究蓝藻中的光养作用来验证这一假说。高价锰物种在环境中构成一个关键的强氧化剂池，参与碳和金属的循环。这项工作将通过研究细菌对锰光营养的氧化作用来加深对现代生物锰氧化以及自然界中高价锰的潜在来源的理解。光养锰氧化将使用遗传易驯化的蓝藻聚球藻的整个细胞进行评估并与生长联系起来。PCC6803和该微生物的一个突变体在光合作用中受损。从这些菌株中提纯的PSII将确定氧化光养作用的化学计量和机制。这些研究有可能为我们理解氧合光合作用的进化提供新的见解。更广泛的影响涉及到研究密集型机构和主要是本科机构之间的研究合作，这些机构也是为少数群体服务的。来自这两个机构的学生将相互互动，研究成果将被纳入本科生和K-12级别的演讲和课程。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。

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.