ALTERNATIVE NITROGENASES: HOW MUCH DO THEY CONTRIBUTE TO N2 FIXATION AND WHY?

GSTDTAP

项目编号	1631814
	ALTERNATIVE NITROGENASES: HOW MUCH DO THEY CONTRIBUTE TO N2 FIXATION AND WHY?
	Anne Kraepiel
主持机构	Princeton University
项目开始年	2016
	2016-07-01
项目结束日期	2019-06-30
资助机构	US-NSF
项目类别	Standard Grant
项目经费	357768(USD)
国家	美国
语种	英语
英文摘要	In terrestrial and marine ecosystems, plant growth is often limited by the availability of the essential element nitrogen. Biological nitrogen fixation, the reaction that transforms nitrogen gas into plant-available ammonium, is a key reaction that controls the fertility of ecosystems on the planet. Nitrogenase, the enzyme (biological catalyst) responsible for this reaction, exists in three different forms, called isoforms. Each isoform has characteristic properties, including different efficiencies, trace metal requirements and optimum temperatures. Yet, their relative contributions to nitrogen fixation in the environment are currently unknown. This project aims at using a newly developed method to improve our understanding of the distribution and activity of the three nitrogenase isoforms. This project will provide a better understanding of the services (such as changes in ecosystem fertility) provided by nitrogen fixation to human societies and how they may evolve into the future. It will also provide important educational training to undergraduate and graduate students, and material for science activities with K-5 students focused on the origin of soil nutrients and their role for plant growth. The three isoforms of nitrogenase are the Mo-nitrogenase, and the V- and the Fe-only nitrogenases (sometimes referred to as the "alternative" nitrogenases). The activity of the alternative nitrogenases can be distinguished from that of the Mo-nitrogenase using a new method (ISARA, for Isotopic Acetylene Reduction Assay), which is a variation on the classic Acetylene Reduction Assay (ARA). The samples are incubated with acetylene, and ethylene production is measured over time to estimate nitrogenase activity. The 13C isotope fractionation of acetylene reduction is diagnostic of whether the Mo- or the alternative nitrogenases carry out the reaction. The proposed project has two components: 1- Determination of the contribution of the three nitrogenase isoforms in coastal marine and boreal ecosystems; 2- Laboratory investigations of alternative nitrogen fixation, with particular focus on delineating the interplay of metal, temperature, and cellular physiological controls on isoform activity. This work will provide the quantitative data on the contribution of alternative nitrogenases to ecosystem nitrogen fixation. It will also shed new light on the controls of alternative nitrogen fixation. If the importance of alternative nitrogen fixation is confirmed, it may require a reexamination of isotope- and ARA-based understanding of the nitrogen cycle on local and global scales.
来源学科分类	Geosciences - Earth Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/69772
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Anne Kraepiel.ALTERNATIVE NITROGENASES: HOW MUCH DO THEY CONTRIBUTE TO N2 FIXATION AND WHY?.2016.