权益分类	功能权益	普通用户	{{item.name}}会员
{{category.name}}	{{benefitItem.name}}

Deciphering the novel link between sulfur assimilation and nitrogen fixation in methanogenic archaea

破译产甲烷古菌中硫同化和固氮之间的新联系

基本信息

批准号：
1817819
负责人：
Daniel Lessner
金额：
$ 68.63万
依托单位：
University of Arkansas
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2018
资助国家：
美国
起止时间：
2018-08-01 至 2024-07-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1817819&HistoricalAwards=false
关键词：
Deciphering novel link between sulfur

项目摘要

Enhanced production of biofuels and crop plants is needed to meet society's ever-increasing demand for fuel, food, and feedstocks. The assimilation of atmospheric nitrogen by cells (nitrogen fixation) requires nitrogenase, an iron-sulfur enzyme found only in prokaryotes (bacteria and archaea). The overall goal of this project is to understand nitrogen fixation in a type of archaea, methanogens, and to decipher its link to sulfur assimilation. Nitrogen is a limiting nutrient in the production of crop plants, and engineering nitrogen-fixation in plants would alleviate the substantial costs and energy needed to chemically produce fertilizers currently used to overcome this limitation. Also, nitrogenase-based technology is a promising strategy to produce biofuels. The research team of high school, undergraduate, graduate, and postdoctoral students will use modern molecular and biochemical techniques to specifically determine the factors that control the sulfur-specific expression and assembly of nitrogenase in methanogens. To understand the scope of the effect of sulfur on nitrogen fixation by methanogens and to integrate the project with teaching, students in an upper-level lab course, taught by the PI, will use sediments from diverse sources to enrich and isolate nitrogen-fixing methanogens. Students in the lab course will gain research experience and contribute directly to the project.All bacteria and archaea capable of nitrogen fixation (diazotrophy) contain molybdenum (Mo) nitrogenase. Some diazotrophs also contain vanadium (V) and iron (Fe) nitrogenases. The maturation of all nitrogenases requires the delivery and assembly of simple and complex iron-sulfur clusters. Thus, diazotrophs need to sense and respond to changes in available sulfur and metals during diazotrophy. In diazotrophic bacteria, the NIF system is required for the biogenesis of the iron-sulfur clusters in nitrogenase, and cysteine serves as the direct sulfur donor. Diazotrophic methanogens lack the NIF system but contain components of the ISC and SUF Fe-S cluster biogenesis systems. Methanogens can also use sulfide as an exogenous sulfur source and as the direct sulfur donor in the biogenesis of iron-sulfur clusters. Initial results with the model methanogen Methanosarcina acetivorans, which contains Mo-, V-, and Fe-nitrogenases, indicate that the exogenous sulfur source (cysteine or sulfide) causes profound differences in nitrogenase expression, inhibition of diazotrophic growth by hydrogen, and usage of ISC and SUF Fe-S cluster biogenesis systems. Thus, the hypothesis is that unlike bacteria, the assimilated sulfur source is a key determinant in the expression, assembly, and activity of nitrogenases in diazotrophic methanogens. A combination of genetic, physiological, biochemical, and transcriptomics approaches will be used with M. acetivorans to test the hypothesis. The specific objectives are to determine the effect of sulfur source on 1) diazotrophic growth and nitrogenase expression, 2) the use of ISC and SUF system components for the assembly of M. acetivorans nitrogenases, and 3) the use of hydrogenase to alleviate inhibition of nitrogenase by H2. The combined results of the project are expected to reveal the molecular factors that link sulfur assimilation to nitrogen fixation by methanogens.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

需要提高生物燃料和作物的产量，以满足社会对燃料、食品和原料不断增长的需求。细胞对大气氮的同化作用（固氮作用）需要固氮酶，这是一种仅在原核生物（细菌和古细菌）中发现的铁硫酶。该项目的总体目标是了解一种古细菌产甲烷菌的固氮作用，并破译其与硫同化的联系。氮是作物生产中的限制性营养素，并且植物中的工程固氮将减轻目前用于克服这种限制的化学生产肥料所需的大量成本和能量。此外，基于固氮酶的技术是生产生物燃料的一个有前途的战略。由高中生、本科生、研究生和博士后组成的研究团队将利用现代分子和生物化学技术，具体确定控制产甲烷菌固氮酶硫特异性表达和组装的因素。为了了解硫对产甲烷菌固氮作用的影响范围，并将该项目与教学相结合，PI教授的高级实验室课程的学生将使用来自不同来源的沉积物来富集和分离固氮产甲烷菌。学生在实验室课程中将获得研究经验，并直接为项目做出贡献。所有能够固氮（固氮）的细菌和古细菌都含有钼（Mo）固氮酶。一些固氮生物还含有钒（V）和铁（Fe）固氮酶。所有固氮酶的成熟都需要简单和复杂的铁硫簇的传递和组装。因此，固氮生物需要在固氮过程中感知和响应有效硫和金属的变化。在固氮菌中，固氮酶中的铁硫簇的生物发生需要NIF系统，半胱氨酸作为直接的硫供体。固氮产甲烷菌缺乏NIF系统，但包含ISC和SUF Fe-S簇生物合成系统的组件。甲烷菌也可以利用硫化物作为外源硫源和铁硫簇生物成因中的直接硫供体。与模型甲烷八叠球菌醋酸，其中包含Mo-，V-和Fe-固氮酶的初步结果表明，外源硫源（半胱氨酸或硫化物）引起固氮酶的表达，抑制固氮生长的氢，和使用ISC和SUF Fe-S簇生物合成系统的深刻差异。因此，假设是，不像细菌，同化的硫源是固氮产甲烷菌固氮酶的表达，组装和活性的关键决定因素。遗传学、生理学、生物化学和转录组学方法的组合将用于M。来验证假设。具体的目标是确定硫源对1）固氮生长和固氮酶表达的影响，2）ISC和SUF系统组件用于组装M.乙酸菌固氮酶，和3）氢化酶的用途，以减轻H2对固氮酶的抑制。该项目的综合结果有望揭示将硫同化作用与产甲烷菌固氮作用联系起来的分子因素。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。