IRFP: Constraining the role of photosynthetic organisms in deposition of Banded Iron Formations (BIF) on early Earth

IRFP：限制光合生物在早期地球带状铁形成（BIF）沉积中的作用

• 批准号: 1064391
• 负责人: Elizabeth Swanner
• 金额: $ 15.43万
• 依托单位: Swanner Elizabeth D
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2011
• 资助国家: 美国
• 起止时间: 2011-10-01 至 2015-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1064391&HistoricalAwards=false
• 关键词: IRFP; Constraining; role; photosynthetic; organisms

The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad. This award will support a twenty-four-month research fellowship by Dr. Elizabeth D. Swanner to work with Prof. Dr. Andreas Kappler at Eberhard Karls Universität Tübingen, Germany. This project addresses two fundamental questions about the co-evolution of Earth's bio- and geochemistry. The first hypothesis proposes that the lag between the evolution of O2-producing cyanobacteria and the irreversible oxidation of the Earth's atmosphere (the Great Oxidation Event, GOE) resulted from physiological limitations of the earliest cyanobacteria that curtailed their initial growth and O2 production. Cyanobacterial growth and O2 production will be assessed under the range of physical and chemical conditions possible in the Archean ocean prior to the GOE (temperature, nutrient, trace metal and light supply) to determine whether they were physiologically constrained. The second hypothesis proposes that an increase in the abundance of cyanobacteria following their adaptation to prevailing ocean conditions explains the disappearance of alternating Fe-Si microbands in Fe(III)-containing banded iron formations (BIF) deposited after the GOE. Prior to the GOE, Fe(III)-bearing BIF deposition is attributed to the activity of Fe(II)-oxidizing photosynthetic bacteria (photoferrotrophs), which generate alternating Fe-Si layers when incubated under the fluctuating temperatures that are predicted for the Archean ocean. If competition for nutrients and light existed between cyanobacteria and photoferrotrophs, as cyanobacteria adapted to prevailing conditions the photoferrotrophs would have been marginalized to less productive depths in the ocean. In that case the primary Fe-oxidation and deposition mechanism would be oxidation by cyanobacterially-produced O2 and not Fe-Si microbands. To evaluate this hypothesis, the growth and activity of cyanobacteria and photoferrotrophs in co-culture will be tracked, and the deposited Fe minerals will be compared to those formed by each organism living alone. These experiments will contribute to our understanding of how the development the biosphere is recorded in the geologic record, and also how the geochemistry of the early oceans influenced microbial evolution. This project will integrate geochemical techniques with physiological measurements, specifically through the use of voltammetric microelectrodes to acquire real-time aqueous Fe, O2 and metal speciation and concentration data, and synchrotron-based X-ray absorption spectroscopy to map the distribution and concentration of cells and metals in precipitated Fe-oxides. In addition, the project will facilitate international collaboration and exchange of ideas between the postdoc and scientists and students of all levels in the host laboratory, as well as with collaborators in Europe. Finally, the results of the project will be used to create written outreach material for primary and secondary students.

国际研究奖学金计划使美国的科学家和工程师能够在国外进行九至二十四个月的研究。该计划的奖项为联合研究提供了机会，以及在国外使用独特或补充设施，专家和实验条件。该奖项将支持伊丽莎白·D·斯旺纳（Elizabeth D.该项目解决了有关地球生物和地球化学共同发展的两个基本问题。第一个假设提出的提议表明，产生O2的蓝细菌的演变与地球大气中不可逆的氧化物（大氧化事件，GOE）之间的滞后是由于最早的蓝细菌的生理局限性导致了其初始生长和O2产生。在GOE（温度，养分，痕量金属和光供应）之前，将在大帝海洋的物理和化学条件范围内评估蓝细菌生长和O2产生，以确定它们是否受到物理的约束。第二个假设提出的提议是，蓝细菌适应以盛行的海洋条件的抽象增加，可以解释出在GOE后沉积的Fe（III）含有带状的铁层（BIF）中替代的Fe-SI微型微型的消失。在GOE之前，Fe（III）含BIF沉积归因于Fe（II）的活性氧化光合细菌（Photofrotrophrophs），当在波动的温度下孵育时，该细菌会产生替代的Fe-SI层，该层可预测为Archean Ocean预测。如果在蓝细菌和光肉芽菌之间存在营养和光的竞争，则随着蓝细菌适应了盛行的条件，光铁嗜性会被边缘化到海洋中生产力较低的深度。在这种情况下，主要的Fe氧化和沉积机制将是由蓝细菌生产的O2而不是Fe-SI微型的氧化。为了评估这一假设，将跟踪蓝细菌和光嗜性养殖在共培养中的生长和活性，并将沉积的Fe矿物与单独生活的每个生物体形成的矿物质进行比较。这些实验将将地球化学技术与物理测量相结合，特别是通过使用伏安级微电极来获取实时水性水，O2和金属规范和浓度数据，以及基于X射线的抽象光谱谱图绘制细胞和金属在珍贵的Fe-氧化物中的分布和浓度。此外，该项目将促进博士后与主机实验室各个级别的科学家和学生之间以及与欧洲的合作者之间的国际合作和交流。最后，该项目的结果将用于为小学和中学生创建书面外展材料。