Studies on phosphorus solubilizing activity of a strain of phosphobacteria isolated from chestnut type soil in China

A phosphorus solubilizing bacterium, designated phosphobacterium 9320-SD, was isolated from field soil in Tianjin, China. Cells of the phosphobacterium 9320-SD were gram-positive, rod shaped, and produced spores. When 9320-SD was inoculated into MPMLM, amended with powdered (insoluble) mineral phosphate as the single P source, and incubated at 30 degrees C, the release of soluble phosphorus increased with increasing amounts of added phosphates over the range of 0.12-4% (w/v). The maximal available phosphorus reached 12.01 mmol P/L after 7 days incubation. Furthermore, there was a direct positive correlation (r = 0.9330) between the level of soluble phosphorus release and the concentration of viable bacteria. SEM study of the phosphate powder retrieved from the phosphobacterium 9320-SD cultured medium revealed the actual dissolution of phosphate from the mineral surface. Phosphobacterium 9320-SD had significant effect (p < 0.05) on winter wheat total P and plant biomass under both pot and field conditions, although no obvious difference in plant height was found compared to the control. Taken together, these results demonstrate that phosphobacterium 9320-SD has the ability to convert non-available forms of phosphorus into plant-available forms, and therefore holds great potential for development as a biofertilizer to enhance soil fertility and promote plant growth.