EAGER: Optimizing Nitrogen Fixation between Bacteria and Legumes in Marginal Soils

在光合作用之后，固氮是地球上最重要的生化反应;这两个过程对生命都是必不可少的。虽然地球大气的78%是双原子氮（N2），但所有生物体都需要氮，但无论是还原（氨）还是有机形式（氨基酸，核酸等）。 植物生长所需的氮主要以商业肥料的形式提供，但由于合成氮肥的生产需要天然气，因此肥料（以及食品）的成本正在增加。某些细菌将N2气体还原或“固定”为氨，作为合成氨基和核酸的起点。 固氮是氮循环的重要组成部分，因此对维持地球的氮平衡至关重要。该项目将测试Burkholderia属的成员，最近发现可以使豆类和豇豆等农业上重要的豆科植物与根瘤菌菌株一起为生长在干旱，酸性或盐碱土壤中的植物提供固定氮，随着气候变化的继续，这将变得更加普遍。我们的方法将是用伯克霍尔德氏菌单独或与根瘤菌菌株一起接种豆科植物，或与新发现的植物生长促进细菌一起接种豆科植物，这些细菌可以改善根系结构以吸收水分或提供有效的磷酸盐或铁，以测试增加的植物生物量，种子产量，芽和根生长，根瘤数量和固氮能力。 将采用遗传工具，包括报告基因融合和诱变以及基因组分析和生理/生化实验。 该项目将为本科生，研究生和博士后学生提供科学培训和批判性思维技能，特别是目前在STEM领域代表性不足的群体成员。 我们的最终目标是减少我们对不可再生化石燃料的依赖，利用有益的微生物与固氮细菌协同作用，即使在最边缘的土壤上也能促进植物生长和产量。

After photosynthesis, nitrogen fixation is the most important biochemical reaction on Earth; both processes are essential for life. Although 78% of the earth's atmosphere is diatomic nitrogen (N2), all living organisms require nitrogen but in either reduced (ammonia) or organic forms (amino acids, nucleic acids, etc.). Nitrogen for plant growth is supplied mostly as commercial fertilizer, but the costs of fertilizer (and with it food) are increasing because synthetic nitrogen fertilizer requires natural gas for its production. Certain bacteria reduce or 'fix' N2 gas into ammonia as the starting point for amino and nucleic acid syntheses. Nitrogen fixation is a crucial component of the nitrogen cycle, and thus essential for maintenance of the planet's nitrogen balance. This project will test members of the genus Burkholderia, recently discovered to nodulate such agriculturally important legumes as bean and cowpea, with Rhizobium strains in terms of providing fixed nitrogen to plants growing in arid, acidic, or saline soils, which will become more widespread as climate change continues. Our approach will be to inoculate legumes with Burkholderia species either singly or together with Rhizobium strains, or together with newly discovered plant growth-promoting bacteria that improve root architecture for water uptake or provide available phosphate or iron, to test for increased plant biomass, seed yield, shoot and root growth, nodule number, and nitrogen fixation ability. Genetic tools including reporter gene fusions and mutagenesis as well as genome analysis and physiological/biochemical experimentation will be employed. This project will provide scientific training and critical thinking skills to undergraduate, graduate, and post-doctoral students, particularly members of groups who are currently underrepresented in STEM fields. Our ultimate goal is to reduce our dependence on non-renewable fossil fuels by utilizing beneficial microbes that act synergistically with nitrogen-fixing bacteria to enhance plant growth and yield even on the most marginal soils.