Solubilization of Inorganic Rock Phosphate by Rhizobacteria of Allium hookeri Thwaites and Influence of Carbon and Nitrogen Sources Amendments

摘要

Phosphate solubilizing bacterial strains [Arthrobacter luteolus S4C7, Klebsiella pneumoniae S4C9, K. pneumoniae S4C10, Enterobacter asburiae S5C7, K. pneumoniae S6C1 and K. quasipneumoniae S6C2) were isolated from the rhizospheric soil of Allium hookeri Thwaites. All the isolates were proved to be positive for rock phosphate (RP) solubilization at different concentration (0.5%, 1.0% and 1.5%). K. pneumoniae S4C10 was found to be most efficient as 81.6 jug/ml of soluble phosphate when amended with 1%of RP, followed by K. quasipneumoniae S6C2 where soluble phosphate release was 76.8 jug/ml in 0.5% RP amended medium. Also, maximum solubilization was noted to correlate with decrease in p" of the medium. Strain A. luteolus S4C7 liberated small amount ofP as compared to other strains. The process of phosphate solubilization was optimized for different carbon sources. Fructose was preferred as best carbon source by K. pneumoniae S4C10 with 85.6 fig/ml of solubilized P in NBRIP broth medium. However, after fructose, glucose also proved to be best carbon source by K. quasipneumoniae S6C2 (83.2 /ig/ml) and K. pneumoniae S6C1 (78.4 /ig/ml) in the NBRIP medium. Among different nitrogen sources, di-ammonium sulphate was found to be best for phosphate solubilization by the strain K. pneumoniae S6C1 (151.2 /ig/ml).