Effect of osmotic stress on the organic Acid production profile and tricalcium phosphate solubilization by osmotolerant bacteria.

Abstract

Osmotolerant Plant Growth Promoting Rhizobacteria (PGPR) playsan important role in plant growth promotion in water stressed environments. Since phosphate solubilisation is one of the major mechanisms of plant growth promotion under water stressed conditions, this study was conducted to determine the effect of osmotic stress on the organic acid production profile and phosphate solubilization abilities of twelve osmotolerant bacterial isolates in NBRIP medium supplemented with 25% PEG 8000 (-1.97 MPa). It was observed that the imposed level of osmotic stress did not significantly affect the production of citric, formic, 2-keto glutaric, lactic, malic, malonic propionic and tartaric acids. Most isolates were able to solubilize tricalcium phosphate more efficiently under in vitroosmotic stress conditions compared to normal conditions. The soluble P released from tri calcium phosphate by the isolates ranged from 2.78-25.22 ppm under non osmotic conditions, while it ranged from 4.67-53.56 ppm under osmotic stress conditions. Amongst the osmotolerant bacterial cultures, Bacillus amyloliquefaciensP-72 recorded significantly higher soluble P concentrations (53.56 ppm) under osmotic stress conditions while the isolate Enterobactersp. P-39 recorded the lowest soluble P concentration (4.98 ppm).