Nitrogenase metal cofactors in terrestrial systems: Chemical speciation and the kinetic versus thermodynamic controls on metal acquisition by diazotrophs using metallophores

弗兰克·j·布莱克博士获得了美国国家科学基金会地球科学博士后奖学金，将在普林斯顿大学开展一项研究和教育计划。该研究将有助于了解土壤和凋落叶中微量金属（Mo和V）的数量和形态如何影响游离固氮细菌的活性，以及这些细菌如何调整其获取金属的策略以适应不同的土壤环境。这项研究的目的是了解(1)在固氮发生的土壤和凋落叶中发现了什么形式的钒和钼，(2)这些不同形式的固氮细菌的可利用性如何，以及(3)细菌在不同土壤条件下获得这些金属的机制更有效。细菌已经发展出各种各样的方法来获取土壤中的铁，甚至从通常无法获得的形式中获取铁，这项研究将测试细菌在类似条件下获取钼和钒的效率。在许多生态系统中，植物的生长和二氧化碳的利用受到营养氮可用性的限制。一些土壤细菌能够固定大气中的氮，并使其成为生物可利用的，但为了做到这一点，它们需要金属钼、钒和铁的组合。这些金属通常在土壤中缺乏（例如钼），或者以细菌不易接近的形式结合（例如铁）。这些金属在土壤环境中的低可利用性是对固氮的潜在重要控制，反过来又对整个生态系统的生产力产生影响。与该项目相关的教学和教育拓展活动将包括使用基于探究的技术帮助设计和教授大一研讨会课程的实验室部分。

Dr. Frank J. Black has been granted the NSF Earth Sciences Postdoctoral Fellowship to carry out a research and education plan at Princeton University. The research will contribute to the understanding of how the amount and forms of trace metals (Mo and V) in soils and leaf litter influence the activity of free living nitrogen fixing bacteria, and how these bacteria tailor their strategies for metal acquisition to adapt to different soil environments. The research to be conducted aims to understand (1) what forms of vanadium and molybdenum are found in soils and leaf litter where nitrogen fixation occurs, (2) how available these different forms are to nitrogen fixing bacteria, and (3) which mechanisms developed by bacteria to acquire these metals are more effective under different soil conditions. Bacteria have developed various approaches to acquiring iron in soils even from normally unavailable forms, and this research will test how effective bacteria are at acquiring molybdenum and vanadium under similar conditions. Plant growth and CO2 utilization in many ecosystems is limited by the availability of the nutrient nitrogen. Some soil bacteria are able to fix nitrogen from the atmosphere and make it bioavailable, but in order to do so they require a combination of the metals molybdenum, vanadium, and iron. These metals are often in short supply in soils (e.g., molybdenum), or are bound in forms not readily accessible to bacteria (e.g., iron). The low availability of these metals in soil environments is a potentially important control on nitrogen fixation, and in turn on the productivity of entire ecosystems. Teaching and educational outreach activities associated with the project will include helping to design and teach the laboratory section of a freshman seminar course using inquiry based techniques.