Controls on Alternative N2 Fixation: Consequences for Land Sequestration of Anthropogenic CO2 and Bio-hydrogen Production

2015 New Investigator Award

Award Period: 2015-2017

The controls on biological N₂ fixation, a key reaction governing the fertility of natural and managed ecosystems, remain poorly understood. Biological N₂ fixation is catalyzed by the nitrogenase enzyme that exists in the canonical form containing the metal molybdenum (Mo) and alternative forms containing vanadium (V) or only iron (Fe) in the active site. Using a new experimental method, researchers Anne Morel-Kraepiel and Xinnang Zhang were able to demonstrate for the first time that the alternative V-nitrogenase and the Fe-only nitrogenase make significant contributions to N₂ fixation in various ecosystems. This finding calls into question the understanding of the controls on alternative nitrogenases. Their preliminary data indicate that the redox status of the N₂-fixing bacteria may control the form of nitrogenase used, in addition to the well-studied conditions of metal availability and/or temperatures. They are currently investigating the interplay of temperature, metal availability and cellular redox status in controlling the type of nitrogenase that is used by N₂-fixers. This work will provide a much-needed understanding of the controls on nitrogen fixation with potential for the long-term storage of anthropogenic CO₂ on land and the development of strategies for biohydrogen production.

Educational Impacts

This research project is carried out in part by Carol Chui, an undergraduate student doing a lab internship in the Morel lab over the summer of 2015 and continuing for her senior thesis. Carol is directly supervised by Xinning Zhang. In addition, the team believe that this project, with its potential application to the production of clean alternative energy, will be highly attractive to students interested in acquiring a first experience with laboratory-based research in the fields of energy and the environment.