The evolutionary history of 16S rDNA sequences from members of the orders Rhodospirillales and Rhizobiales. The tree was constructed using the Neighbor-Joining method with 1000 bootstrap replicates (percentages greater than 50% are shown next to the branches). The tree is drawn to scale, with branch lengths in the same units as those of the evolutionary distances used to infer the phylogenetic tree. There were a total of 1254 positions in the final dataset. The species Azospirillum amazonense is indicated by an arrow. The gray boxes indicate members of the order Rhodospirillales.