Taxonomic and Ecologic Studies of Diazotrophic Rhizosphere Bacteria Using Phylogenetic Probes

The phylogenetic relationships between diazotrophic rhizosphere bacteria were studied using 16S and 23S ribosomal RNA sequences. Certain stretches of the rRNA sequences are variable enough to provide information for the development of diagnostic probes at the species level for the five Azospirillum spp., Acetobacter diazotrophicus, Herbaspirillum seropedica, H. rubrisubalbicans and „isolate E“-bacteria. The brasilian „isolate E“- type bacteria, which reside inside roots, stems and leaves of several plants, could be grouped into the beta-subgroup of proteobacteria. According to their 16S rRNA sequences they belong to the genus Burkholderia. Recently isolated diazotrophic bacteria from the C4-plants Miscanthus sinensis and Spartina pectinata were identified as Azospirillum lipoferum and Herbaspirillum-like bacteria.