USE OF 16S rRNA GENE FOR CHARACTERIZATION OF PHOSPHATE-SOLUBILIZING BACTERIA ASSOCIATED WITH CORN

Abstract

Thirty-six strains of phosphate-solubilizing bacteria (PSB) isolated from the rhizosphere and rhizoplane of corn (Zea mays L.) crops in different states of México were subjected to phenotypic and genotypic characterization. The phosphate-solubilizing activity of each strain was first evaluated using tricalcium phosphate as the phosphorus source in the NBRIP-BPB culture medium. Phosphatesolubilizing capacity was also evaluated by adding the pH buffering agent MES (2-[Morpholine] ethanosulfonic acid) to the growth medium. Amplified ribosomal RNA restriction pattern analysis (ARDRA) was used to evaluate the genetic diversity. From the data matrix obtained, a dendrogram was built using the UPGMA method. The 16S rRNA gene of the BUAP29, BUAP36 and CP08 strains was amplified, cloned and sequenced for taxonomic identification. The 36 bacterial strains exhibited different levels of tricalcium phosphate solubilizing activity. Only BUAP33, BUAP17 and BUAP21 strains did not show the typical solubilization halo when the MES buffering agent was added to the growth medium. The analysis of ARDRA patterns as well as the dendrogram exhibited a large genetic diversity among the 36 PSB analyzed, with BUAP36 and BUAP15 strains showing 100 % similarity. The 16S rRNA gene sequence alignment of CP08, BUAP29 and BUAP36 strains showed 99 % identity with the sequences of Advenella incenata strain R-16599 (NCBI accession number AY569458.1), Burkholderia sp (NCBI accession number AY353696) and Burkholderia gladioli strain 223-1 (NCBI accession number DQ355168.1), respectively. In this study the A. incenata strain is reported as a PSB for the first time.