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。这项研究将有助于理解土壤和凋落物中痕量金属(Mo和V)的数量和形态如何影响自由生活的固氮菌的活性，以及这些细菌如何调整它们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)在发生固氮作用的土壤和凋落物中发现了哪些形式的钒和钼，(2)这些不同的形式对固氮菌的作用如何，以及(3)在不同的土壤条件下，细菌开发的获取这些金属的机制更有效。细菌已经开发出各种方法来获取土壤中的铁，即使是从通常不可用的形式，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，植物的生长和对二氧化碳的利用受到营养氮素有效性的限制。一些土壤细菌能够固定大气中的氮并使其生物可用，但要做到这一点，它们需要金属钼、钒和铁的组合。这些金属在土壤中往往供不应求(例如钼)，或者以细菌不易接触到的形式结合(例如铁)。这些金属在土壤环境中的低有效性对固氮，进而对整个生态系统的生产力具有潜在的重要控制作用。与该项目有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.