K3解磷菌的解磷机理及其对缓冲容量的响应

以对磷酸三钙具有高效溶解作用且对玉米苗生长有促生效果的假单胞菌K3为模式菌株，采用NBRIP液体培养基研究了解磷菌K3的解磷机制及缓冲容量对其解磷量的影响。结果表明，解磷菌K3液体摇瓶培养7 d后，培养液中水溶性磷从6.54 μg/mL增加至655.23 μg/mL，pH从7.00降至3.99。高效液相色谱测定发现，K3菌液中的主要代谢产物为苹果酸、乳酸和草酸，浓度分别为47.39 mmol/L、25.67 mmol/L和1.89 mmol/L。人工模拟K3菌株产生的有机酸及调节培养基不同pH值对磷酸三钙溶解度影响的试验表明，有机酸的螯合作用是解磷细菌K3菌株解磷的主要机理，而调节培养基pH对解磷的作用有限。液体摇瓶和土培试验结果显示，土壤缓冲容量对K3解磷菌的解磷效应有显著的抑制作用。

Mechanism on phosphate solubilization of Pseudomonas sp. K3 and its phosphate solubilization ability under buffering condition

Pseudomonas sp. K₃ was identified with a high ability for solubilizing tricalcium phosphate (TCP) and enhances the growth of maize seedling. This study investigated the mechanism of phosphate solubilization and assesses the influence of buffer capacity under in vitro condition on the phosphate solubilizing ability of K₃. We collected filtrates from 7 days incubation in a liquid medium NBRIP, and found that the P concentration in the solution increased from 6.54 μg/mL to 655.23 μg/mL, when the pH decreased from 7.00 to 3.99. Results form HPLC-analysis showed that the solubilization of TCP was mainly caused by the release of 47.39 mmol/L malic acid, 25.67 mmol/L lactic acid and 1.89 mmol/L oxalic acid. At these concentration, malic acid, lactic acid and oxalic acid could solubilizing 535.31μg/mL, 279.06 μg/mL and 46.58 μg/mL P from TCP, respectively. It demonstrated that organic acid excretion by K₃ was the main mechanism for P solubilization. Liquid culture and soil incubation experiments showed that the buffering capacity of soil could limit the solubilization of insoluble phosphate by K₃ strain.