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

Frank J. Black 博士已获得美国国家科学基金会地球科学博士后奖学金，在普林斯顿大学开展研究和教育计划。该研究将有助于了解土壤和落叶层中微量金属（钼和钒）的数量和形式如何影响游离固氮细菌的活性，以及​​这些细菌如何调整其金属获取策略以适应不同的土壤环境。 即将进行的研究旨在了解（1）发生固氮的土壤和落叶中存在哪些形式的钒和钼，（2）固氮细菌如何利用这些不同形式的钒和钼，以及（3）细菌为获取这些金属而开发的哪些机制在不同的土壤条件下更有效。 细菌已经开发出多种方法来获取土壤中的铁，甚至可以从通常无法获得的形式获取铁，这项研究将测试细菌在类似条件下获取钼和钒的有效性。 许多生态系统中的植物生长和二氧化碳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可供生物利用，但要做到这一点，它们需要金属钼、钒和铁的组合。 这些金属在土壤中通常供应不足（例如钼），或者以细菌不易接触的形式结合（例如铁）。 土壤环境中这些金属的低可用性是对固氮的潜在重要控制，进而影响整个生态系统的生产力。与该项目相关的教学和教育外展活动将包括使用基于探究的技术帮助设计和教授新生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.