石灰性土壤解磷细菌的鉴定及其对土壤无机磷形态的影响
Identification of PSB and their impact on soil inorganic phosphorus

【目的】从北方石灰性土壤中分离筛选解磷细菌，对其进行鉴定，并测定其解磷能力，为筛选高效稳定的解磷菌株提供参考。【方法】采集陕西杨凌地区白菜、葡萄、猕猴桃3种植物根际土样，采用稀释涂布法分离土壤解磷细菌，对分离到的细菌进行革兰氏染色，观察菌落形态及颜色，测定其生理生化性质，并结合16S rRNA法对其进行鉴定；测定各菌株在固体及液体培养基中的解磷能力大小；分析浇灌无机解磷细菌发酵液后石灰性土壤中无机磷形态及其含量的变化。【结果】共分离筛选得到10株解磷细菌，其中2株为有机解磷细菌(Y1和Y2)，4株为无机解磷细菌(W1、W2、W3和W4)，其余4株既能分解有机磷，也能分解无机磷，为双解磷细菌(WY1、WY2、WY3和WY4)；分离到的10株解磷细菌为革兰氏阴性菌，其中WY1和Y2为短杆菌，其余均为杆菌。生理生化性质及16S rRNA序列分析结果表明，10株菌株中 8株属于芽孢杆菌属(Bacillus)，其中WY2、W1、W2、W3与腊状芽孢杆菌相似，WY3和W4与苏云金芽孢杆菌相似，WY4与巨大芽孢杆菌相似，Y2与Bacillus aryabhattai相似；WY1和Y1分别与耐寒短杆菌、杨氏柠檬酸杆菌相似。不同类型解磷细菌在固、液体培养基中解磷能力不同；高效液相色谱分析结果表明，筛选得到的无机解磷细菌部分分泌草酸，部分分泌酒石酸。石灰性土壤浇灌无机解磷细菌发酵液后，Ca8-P、Ca2-P含量增加，Fe-P含量减少，Al-P、Ca10-P、O-P含量变化不大。【结论】石灰性土壤中解磷细菌具有物种多样性，无机解磷细菌能使石灰性土壤中可利用有效磷含量增加。
【Objective】This study isolated phosphate-solubilizing bacteria (PSB) from northern calcareous soils,investigated their species, and detected their ability of solubilizing fixed phosphorus to provide reference for screening highly efficient and stable solubilizing strains.【Method】Soil samples were collected from the rhizosphere of Brassica rapa chinensis,Actinidia chinensis and Vitis vinifera in Yangling,Shaanxi province.The soil bacteria were isolated by dilution plate method.Gram stain was employed to observe the bacteria appearance.Physicochemical properties of strains were also measured and combined with the 16S rRNA gene sequencing and blasting to identify the strains.Then the phosphate-solubilizing ability of each strain on solid and liquid medium was detected.After being cultured in liquid medium,inorganic phosphorus morphologies were determined in calcareous soil.【Result】Ten PSB strains were obtained with 2 of them were organic phosphate solubilizing bacteria:Y1 and Y2,4 strains were inorganic phosphate-solubilizing bacteria:W1,W2,W3 and W4,and 4 strains with capacity of dissolving both inorganic and organic phosphorus:WY1,WY2,WY3,and WY4.Eight of 10 strains were bacillus while the other 2 strains were bacillus brevisthe.Based on physicochemical properties and 16S rRNA sequence analysis,1 strain belonged to Citrobacter youngae,1 belonged to Brevibacterium frigoritolerans,while the other 8 were Bacillus.Among the 8 Bacillus strains,4 were similar to Bacillus cereus,1 belonged to Bacillus megaterium,1 was Bacillus aryabhattai,and 2 were Bacillus thuringiensis.After the inoculation of inorganic phosphate-solubilizing bacteria,the contents of Ca8-P and Ca2-P increased,the content of Fe-P decreased,while the contents of Al-P,Ca10-P and O-P changed slightly.【Conclusion】PSB of calcareous soil were diverse,and inorganic PSB of calcareous soil increased available phosphorus