Subcellular visualization of the distribution of atmospheric dinitrogen fixed by <i>Gluconacetobacter diazotrophicus</i> bacteria in maize

Abstract Plants normally obtain the nitrogen required for growth through their roots, often after application of synthetic fertilizer to the soil, at great cost to the environment and climate. Inoculation of plant seeds with nitrogen-fixing bacteria is a promising alternative means of supplying plants the nitrogen they require in an environmentally friendly manner. When maize seeds inoculated with nitrogen-fixing Gluconacetobacter diazotrophicus (Gd) are grown for two weeks in a 15 N 2 air environment, nanoscale secondary ion mass spectrometry (NanoSIMS) imaging shows the distribution of fixed nitrogen with subcellular resolution, with the majority being incorporated heterogeneously into chloroplasts. Chloroplasts, as the chief energy source that drives plant growth via photosynthesis, are vital for healthy plant growth and these results help explain the observations of enhanced growth rates in plants containing this nitrogen fixing bacteria. The methodology provides a template upon which more powerful, correlative studies combining genomic and/or spatial transcriptomic methods may be based.