Genomes from sixty-six Bradyrhizobium spp. isolates from forest soils from across North America were sequenced, representing one of the most abundant taxa in across all forest soils.

Members of Bradyrhizobiaceae and in particular Bradyrhizobium are one of the most abundant taxonomic groups identified through sequencing surveys of forest soil bacterial communities. In general they are one of the most abundant soil bacterial groups across a variety of environments. We isolated and sequenced 66 Bradyrhizobium from organic and mineral layers of forest soils in British Columbia, Ontario, California and Texas to characterize the core genome relative to the diversity of the pangenome. Contrary to expectations, none of the assembled isolate genomes possessed genes encoding nitrogenases. The pangenome was extensive across sites and differences were detected in isolates from mineral vs. organic layers. Validation of substrate-utilization and other features of these isolates was made challenging by the nature of these slow-growing organisms which generally fail to grow in liquid culture. These genomes provide a comprehensive insight into these poorly understood and highly abundant soil bacteria.