Phosphate solubilization by endophytic bacteria isolated from banana trees

ABSTRACT Forty isolates of endophytic bacteria isolated from banana tree roots were assessed as to their capacity to solubilize phosphate in a solid culture medium supplemented with different inorganic and one organic source of phosphorus. The amount of phosphorus (P) in each liquid medium was quantified, and an indirect assessment of acid phosphatase activity was performed. All assays had a fully randomized design, with three repetitions. Approximately 67.5% of the 40 isolates assessed in solid medium solubilized phosphorus from tricalcium phosphate and 7.5% of the isolates solubilized phosphorus from soy lecithin; no isolates exhibited P solubilization capacity in medium supplemented with iron phosphate. Acid phosphatase activity was detected in 65% of the isolates; Aneurinibacillus sp. and Lysinibacillus sp. isolates presented with the best solubilization indexes. All of the assessed isolates exhibited a capacity to reduce the potential of hydrogen in liquid medium supplemented with tricalcium phosphate. Isolate EB. 78 (Bacillus sp.) exhibited P solubilization capacity in solid media when Ca3(PO4)2 and soy lecithin were used as P sources; this isolate significantly reduced the pH of the liquid medium and exhibited acid phosphatase activity. The results of the present study highlight isolates that exhibit variations in their capacity to solubilize P. These isolates should be used in future tests to assess their field performance.

摘要 本研究以从香蕉树根中分离得到的40株内生细菌（endophytic bacteria）为材料，评估其在添加不同无机磷源与1种有机磷源的固体培养基中的磷酸盐溶解能力。对各液体培养基中的磷（P）含量进行定量，并间接检测了酸性磷酸酶活性。所有试验均采用完全随机设计，设置3次生物学重复。在固体培养基中测试的40株菌株里，约67.5%可溶解磷酸三钙中的磷，7.5%的菌株可溶解大豆卵磷脂中的磷；未发现有菌株在添加磷酸铁的培养基中具备溶磷能力。65%的菌株检测到酸性磷酸酶活性；嗜氨芽孢杆菌属（Aneurinibacillus sp.）与赖氨酸芽孢杆菌属（Lysinibacillus sp.）菌株表现出最优的溶磷指数。所有供试菌株在添加磷酸三钙的液体培养基中均能降低培养基的pH值。菌株EB.78（芽孢杆菌属（Bacillus sp.））在以磷酸三钙与大豆卵磷脂作为磷源的固体培养基中均表现出溶磷能力；该菌株可显著降低液体培养基的pH值，并检测到酸性磷酸酶活性。本研究结果凸显了溶磷能力存在差异的菌株，此类菌株可用于后续田间性能评估试验。