Phosphate solubilization of Bacillus megaterium isolated from non-saline soils under salt stressed conditions

Abstract

Phosphate solubilizing Bacillus megaterium was isolated from non rhizospheric soils. Five isolates were identified by 16s rDNA sequencing. According to sequencing and phylogenetic tree analysis, these five isolates were in high similarity with B. megaterium. Abiotic stresses such as temperature, pH and salt tolerance of five strains were examined for the application for abiotic stressed agricultural soils. All five strains could grow well above 40ºC. For pH, five strains demonstrated their growth on minimal media at pH 9 but the growth rates were decreased. Among abiotic stress factors, to obtain salt tolerance phosphate solubilizing B. megaterium was the main objective of this research work. So, salt tolerance of isolates were screened preliminary, all five strains had the ability to grow on minimal media containing 6% NaCl concentration but the growth rates were not in high rates. Preliminary screening results enhanced to continue for quantative determination of phosphate solubilization under salt stressed conditions. In detection of phosphate solubilization by the method of Olsen P, all five strains could solubilize insoluble phosphate, Tricalcium phosphate, under NaCl stressed conditions. Among 4%, 5% and 6% NaCl concentrations, soluble phosphate concentrations released by five strains were decreased with increasing NaCl concentrations, but it was not obviously different.