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

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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.