We isolated and characterized novel insoluble phosphate (P)-solubilizing bacteria tolerant to environmental factors like high salt, low and high pHs, and low temperature. A bacterium M6 was isolated from a ginseng rhizospheric soil and confirmed to belong to Burkholderia vietnamiensis by BIOLOG system and 16S rRNA gene analysis. The optimal cultural conditions for the solubilization of P were 2.5% (w/v) glucose, 0.015% (w/v) urea, and 0.4% (w/v) MgCl2 center dot 6H(2)O along with initial pH 7.0 at 35A degrees C. High-performance liquid chromatography analysis showed that B. vietnamiensis M6 produced gluconic and 2-ketogluconic acids. During the culture, the pH was reduced with increase in gluconic acid concentration and was inversely correlated with P solubilization. Insoluble P solubilization in the optimal medium was about 902 mg l(-1), which was approximately 1.6-fold higher than the yield in NBRIP medium (580 mg l(-1)). B. vietnamiensis M6 showed resistance against different environmental stresses like 10-45A degrees C, 1-5% (w/v) salt, and 2-11 pH range. The maximal concentration of soluble P produced by B. vietnamiensis M6 from Ca-3(PO4)(2), CaHPO4, and hydroxyapatite was 1,039, 2,132, and 1,754 mg l(-1), respectively. However, the strain M6 produced soluble P with 20 mg l(-1) from FePO4 after 2 days and 100 mg l(-1) from AlPO4 after 6 days, respectively. Our results indicate that B. vietnamiensis M6 could be a potential candidate for the development of biofertilizer applicable to environmentally stressed soil.