Lakshmibala Kshetri1*, PiyushPandey1,GauriDutt Sharma2

1Department of Microbiology, Assam University, Silchar-788011, Assam, India
2Bilaspur University, Bilaspur, Chattisgarh, India


(Received: 25 October 2017; accepted: 14 December 2017)


Phosphate solubilizing bacterial strains (Arthrobacterluteolus S4C7, Klebsiellapneumoniae S4C9, K.pneumoniae S4C10, Enterobacterasburiae S5C7, K.pneumoniae S6C1 and K.quasipneumoniae S6C2) were isolated from the rhizospheric soil of Allium hookeriThwaites. 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 µg/ml of soluble phosphate when amended with 1% of RP, followed by K. quasipneumoniae S6C2 where soluble phosphate releasewas76.8µg/ml in 0.5% RP amended medium. Also, maximum solubilization was noted to correlate with decrease in pHof the medium. Strain A. luteolus S4C7 liberated small amount of P as compared to other strains. The process of phosphate solubilization was optimizedfor different carbon sources. Fructose was preferred as best carbon source by K. pneumoniae S4C10 with 85.6 µg/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 µg/ml) and K. pneumoniae S6C1 (78.4 µg/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 µg/ml).


Phosphate solubilizing bacteria; rock phosphate; carbon; nitrogen