玉米根内和根际土壤溶磷细菌生物学特性研究

从玉米根内和根际土壤中分离筛选到22株溶磷细菌。根据16SrRNA基因序列分析,2株溶磷效果最好的菌株分别被鉴定为伯克霍尔德氏菌(Burkholderia sp.SY9)和泛菌(Pantoea sp.Gym7c)。同时对菌株SY9和Gym7c的溶磷能力和植物促生特性进行了进一步研究。利用磷酸钙和开阳磷矿矿粉研究了菌株释放P、Ca和Fe的效能。液体培养条件下,菌株在在磷酸钙培养基中的生长好于在开阳磷矿粉培养基中的生长,同时菌株能够合成铁载体。菌株SY9从开阳磷矿粉中释放P、Ca,和Fe的能力比菌株Gym7c强。然而菌株Gym7c从磷酸钙中释放P和Ca的能力比菌株SY9强。菌株Gym7c主要是通过合成的有机酸溶解磷酸钙并释放其中的P和Ca,而菌株SY9是通过合成的有机酸和铁载体溶解开阳磷矿粉并释放出其中的P、Ca,和Fe。溶解开阳磷矿粉的有机酸主要是葡萄糖酸而溶解磷酸钙的有机酸主要包括丁二酸、丙酸、苹果酸和酒石酸等。菌株Gym7c能够合成生长素、铁载体和1-氨基环丙烷-1-羧酸脱氨酶。菌株SY9和Gym7c对酸碱、盐和温度均表现出一定的抗性。

Characterization of Phosphate-Solubilizing Bacteria from Maize Roots and Rhizosphere Soil

Twenty-two phosphate-solubilizing bacteria were isolated from the roots and rhizosphere soil of maize plants. Two best phosphate solubilizers (strain SY9 from rhizosphere soil and strain Gym7c from the root interior) were identified as Burkholderia sp. SY9 and Pantoea sp. Gym7c based on partial 16S rRNA gene sequence analysis, respectively. The two isolates were further characterized phenotypically by their phosphate solubilization and plant growth-promoting characteristics. Tricalcium phosphate and Kaiyang rock phosphate were used to investigate P, Ca and Fe mobilization by the isolates. In liquid cultures, the strains showed better growth on the tricalcium phosphate than on Kaiyang rock phosphate. CAS assay solution analysis showed the siderophores were produced by the two isolates in the presence of the two rock phosphates. Strain SY9 released more P, Ca, and Fe from Kaiyang rock phosphate than strain Gym7c did. However, in the presence of tricalcium phosphate, strain Gym7c could release more P and Ca than strain SY9. Solubilization of P and Ca from tricalcium phosphate by Gym7c resulted mostly from the action of organic acids, and solubilization of P, Ca, and Fe from Kaiyang rock phosphate by SY9 may result from the actions of organic acids and siderophores. Gluconic acid seemed to be a more active agent for the solubilization of the Kaiyang rock phosphate. Succinic, propionic, malic and tartaric acids were likely involved in the solubilization of tricalcium phosphate. Strain Gym7c produced indole acetic acid, siderophores and 1-aminocyclopropane-1-carboxylate deaminase. The two strains could be acidic or alkaline and salt tolerant and temperature resistant.