Genetic diversity of Azotobacter strains isolated from various soils of Poland

Free-living nitrogen-fixing bacteria belonging to the genus Azotobacter are microorganisms commonly occurring in soil. The genus Azotobacter includes 8 species, with Azotobacter chroococcum most commonly inhabiting many soils all over the world. This study aims to isolate and to identify the Azotobacter bacteria from various soils of Poland using RFLP analysis of the bacterial Internal Transcribed Spacer (ITS) region and 16S rRNA gene sequence analysis. 56 strains were isolated from tested soils, using the dilution-pour plates method. Restriction analysis of the bacterial ITS region was used for the characterization and differentiation of the isolated strains. It indicated that the studied isolates were not identical. Among the 56 tested strains, 36 were characterized by the same genotype in ITS-PCR/RFLP analyzes as the reference strains A. chroococcum DSM281 and DSM2286. For molecular identification of the isolates, the 16S rRNA gene was amplified using 27f and 1492r primers and PCR products were sequenced. These results indicate that the analyzed isolates from Polish soils belong to one species, namely Azotobacter chroococcum.