Isolation, characterization and identification of phosphateand potassium- solubilizing bacteria from weathered materials of granite rock mountain, That Son, An Giang province, Vietnam

Abstract

Two hundred and thirty-seven bacterial isolates from 118 sample soils/weathered granite rock of That Son Mountain, An Giang province, Vietnam were isolated on Aleksandrov medium. Their colonies were round or irregular, white to yellow and their shape was rod, motile. Thirty four of two hundred and thirty-seven bacterial isolates were capable of dissolving both phosphate and potassium and seven strains had high phosphate and potassium dissolution capacity (>15 mg 1⁻¹ P₂O₅ and >10 mg 1⁻¹ K₂O). These thirty four strains were identified by using PCR technique with specific primers fd1 and rP and DNA sequencing. The results of DNAsequencing were compared with GenBank database of NCBI by BLAST N software. The sequences from selected phosphate and potassium isolates (34 isolates) showed high degrees of similarity to those of the GenBank references (between 99% and 100%). Among these sequenced isolates, 8 isolates belong to Bacilli (23.53%) and 26 isolates belong to Proteobacteria (76.47%) including 21 alpha-proteobacteria (61.76%) and 5 gamma-proteobacteria (14.71%). Based on Pi value (nucleotide diversity), Proteobacteria group had the highest Theta values and Theta values (per sequence) from S of SNP for DNA polymorphism were calculated for each group and AlphaProteobacteria group had the highest values in comparistion with two groups. These results showed that 3 strains including CA09 (Agrobacterium tumefaciens), CA29 (Rhizobium tropici) and K16B (Azotobacter tropicalis) proposed as potential microbial inoculants or biofertilizers for sustainable crop production in sandy acid soil in Vietnam because of their benefits and biosafety.