SRA

The bacterial genus Bradyrhizobium mostly consists of N2-fixing members that nodulate legumes. Recent environmental surveys show that Bradyrhizobium can also adapt to a free-living lifestyle in many other habitats. Here, we report the genomes of 93 Bradyrhizobium strains derived from diverse soil samples, which greatly expands the known genetic and ecological diversity of this genus. Notably, we showed that horizontal gene transfer (HGT) of a unique nif island among free-living members may have facilitated their transitions from symbiotic lifestyle and adaptation to soil habitats.