| Summary: | Dual flagellar systems have been described in several bacterial genera, but the extent of their prevalence has not been fully explored. <i>Bradyrhizobium diazoefficiens</i> USDA 110<sup>T</sup> possesses two flagellar systems, the subpolar and the lateral flagella. The lateral flagellum of <i>Bradyrhizobium</i> displays no obvious role, since its performance is explained by cooperation with the subpolar flagellum. In contrast, the lateral flagellum is the only type of flagella present in the related <i>Rhizobiaceae</i> family. In this work, we have analyzed the phylogeny of the <i>Bradyrhizobium</i> genus by means of Genome-to-Genome Blast Distance Phylogeny (GBDP) and Average Nucleotide Identity (ANI) comparisons of 128 genomes and divided it into 13 phylogenomic groups. While all the <i>Bradyrhizobium</i> genomes encode the subpolar flagellum, none of them encodes only the lateral flagellum. The simultaneous presence of both flagella is exclusive of the <i>B. japonicum</i> phylogenomic group. Additionally, 292 <i>Rhizobiales</i> order genomes were analyzed and both flagellar systems are present together in only nine genera. Phylogenetic analysis of 150 representative <i>Rhizobiales</i> genomes revealed an uneven distribution of these flagellar systems. While genomes within and close to the <i>Rhizobiaceae</i> family only possess the lateral flagellum, the subpolar flagellum is exclusive of more early-diverging families, where certain genera also present both flagella.
|
|---|