Figure 1.

Genes involved in nitrogen fixation. Top- A. vinelandii nif gene regions. Gray-shaded trapezoids are essential genes in Mo-dependent nitrogen fixation that were used as queries for the in silico identification of nitrogen fixing species described in this study. Bottom –The proposed minimum set of genes required for nitrogen fixation. All species with sequenced genomes that are known diazotrophs and all the species proposed to be diazotrophs based on genetic content contain the minimum gene set.