Nitrogen fixation and transcriptome of a new diazotrophic Geomonas from paddy soils

The ability of Geomonas species to fix nitrogen gas (N₂) is an important metabolic feature for its application as a plant growth-promoting rhizobacterium. This research is of great importance as it provides the first comprehensive direct experimental evidence of nitrogen fixation by the genus Geomonas in pure culture. We isolated a number of Geomonas strains from paddy soils and determined that nifH was present in these strains. This study demonstrated that these Geomonas species harbored genes encoding nitrogenase, as do Geobacter and Anaeromyxobacter in the same class of Deltaproteobacteria. We demonstrated N₂-dependent growth of Geomonas and determined regulation of gene expression associated with nitrogen fixation. The research establishes and advances our understanding of nitrogen fixation in Geomonas.