Collaborative Research: Acquisition of nitrogenase metal cofactors in soils: role of metallophores and limitation of N2-fixation

合作研究：土壤中固氮酶金属辅助因子的获取：金属团的作用和固氮的限制

• 批准号: 1024545
• 负责人: Anthony Aufdenkampe
• 金额: $ 3.4万
• 依托单位: Stroud Water Research Center
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1024545&HistoricalAwards=false
• 关键词: Collaborative; Research; Acquisition; nitrogenase; metal

Intellectual merit: N2 fixation is effected exclusively by bacteria and archea using the enzyme nitrogenase, which contains Fe and Mo as metal cofactors in its most active form, and Fe and V, or Fe-only in its alternative forms. The aim of this project is to elucidate how the mechanisms and kinetics of bacterial acquisition of Fe, Mo and V from soils may limit or control N2 fixation rates. N2-fixing bacteria produce siderophores (or ?iron carriers?) to bind iron in the external medium and take up the resulting Fe-siderophore complexes. Our recent work has shown that the siderophores are actually ?metallophores? used in the uptake of Mo and V, along with Fe. The biological acquisition of the various nitrogenase metal cofactors thus depends on their binding by bacterial metallophores. This project is organized around two major hypotheses: 1. Free-living N2-fixing bacteria excrete metallophores that are particularly efficient at capturing the metal (Mo, V or Fe) that is limiting N2 fixation; 2. Because of both competition with other metals for metallophore binding and scarcity in soils, Mo is inherently difficult to acquire and free-living N2-fixing bacteria often use alternative nitrogenases, particularly the V-nitrogenase, to fix N2. These hypotheses will be tested through a combination of laboratory and field experiments. Field studies will focus on sites where Mo may be limiting and employ molecular biological techniques to identify alternative nitrogenases.Broader Impacts: One postdoctoral researcher, one graduate student and several undergraduates will work on this project and be mentored by the PIs. Students from the local junior colleges will participate in the summer field research. The PIs will participate in the Quest summer program for school teachers.

智力优点：N2 固定仅由细菌和古细菌使用固氮酶实现，其中最活跃的形式包含 Fe 和 Mo 作为金属辅因子，以及替代形式的 Fe 和 V 或仅含 Fe。该项目的目的是阐明细菌从土壤中获取铁、钼和钒的机制和动力学如何限制或控制氮固定率。固氮细菌产生铁载体（或“铁载体”？）以结合外部介质中的铁并吸收由此产生的铁-铁载体复合物。我们最近的工作表明，铁载体实际上是“金属载体”。用于吸收 Mo 和 V 以及 Fe。因此，各种固氮酶金属辅助因子的生物获取取决于它们与细菌金属载体的结合。该项目围绕两个主要假设进行组织： 1. 自由生活的固氮细菌分泌金属团，这些金属团在捕获限制 N2 固定的金属（Mo、V 或 Fe）方面特别有效； 2. 由于与其他金属竞争金属基团结合以及土壤中的稀缺性，钼本质上很难获得，并且自由生活的固氮细菌经常使用替代固氮酶，特别是 V-固氮酶来固定 N2。这些假设将通过实验室和现场实验相结合的方式进行检验。实地研究将集中在 Mo 可能受到限制的位点，并采用分子生物学技术来识别替代固氮酶。更广泛的影响：一名博士后研究员、一名研究生和几名本科生将参与该项目并接受 PI 的指导。来自当地专科学校的学生将参加暑期实地研究。 PI 将参加针对学校教师的 Quest 暑期项目。