| Phosphate-solubilizing bacteria (PSB) were isolated from the rhizosphere soils. These bacteria were identified as Enterobacter agglomerans using API 20E;HPLC results identified oxalic acid as the main organic acid along with several other organic acids released by E. agglomerans. The released acids highly solubilized HY in broth culture media. When phosphate solubilization by E. agglomerans was compared with that by HCl, citric acid, oxalic acid, and lactic acid, a high P concentration was shown in E. agglomerans growing for 84 hours despite similar pH.;To examine the effect of organic energy sources on survival of E. agglomerans and soil microbial activities, E. agglomerans was introduced into soil containing organic energy sources and HY. Acid and alkaline phosphatase activities and soil microbial biomass C in glucose (GL) and soluble starch (SS) treatments were greater compared to phytic acid (PA) and glycerol-2-phosphate (GP) treatments; however, P concentration was greater in PA and GP treatments. When no organic C sources were added into soil, E. agglomerans introduced was not detectable after day 22.;To examine the effects of mycorrhizae and PSB on tomato growth and soil microbial activities, tomato seedlings were grown in non-sterile soil containing HY and glucose inoculated with E. agglomerans (E), Glomus etunicatum (G), a combination of both E and G (E + G), or control without any microorganism (C). P concentration was similar in all treatments over time. The P concentration was greatest in all treatments at 55 d. Alkaline phosphatase activity was higher in G and E + G compared with C at 35 and 55 days. Highest acid phosphatase activity was observed in E at 35 days. High concentrations of oxalic and acetic acids were detected in the rhizosphere of the non-sterile soil. Highest N and P uptake and plant growth were observed in E + G. This study suggests a synergistic interaction between E and G. |
