Phylogenetic studies of the genus Azospirillum

The 16S rDNA of seventeen Azospirillum strains, fourteen of which assigned to one of known A. amazonense, A. brasilense, A. halopraeferens, A. irakense and A. lipoferum species, and other three of uncertain taxonomic collocation, was sequenced and analysed after polymerase chain reaction amplification, in order to investigate the phylogenetic relationships at the intra-generic and super-generic level. Moreover the use of histidine biosynthetic genes and of anonymous sequences generated by RAPD technique to infer phylogenetic relationships among Azospirillum strains is also described. The relationships among the five species, as revealed by DNA sequence data, appeared to be congruent with other molecular and phenotypic results, showing that the genus Azospirillum constitutes a phylogenetically separate entity in which A. brasilense and A. lipoferum are very close species, whereas the species A. amazonense is the most divergent.