Bacterial strain A3 with high ability of producing siderophore was isolated from rhizosphere of greenhouse vegetables.The relative siderophore content was measured by chrome azurol S（CAS） assay and was identified using the Shenker＇s test.The results show that the relative siderophore content is 93.40% and the type is a kind of carboxylate type siderophore.In addition,the strain A3 also has a high ability of solubilizing phosphate and is able to produce indol-3-acetic（IAA） and 1-aminocyclopropane-1-carboxylate（ACC） deaminase under different substrates.According to the morphological,physiological-biochemical properties,API system and the 16S rRNA sequence analysis,the strain A3 is identified as Pseudomonas putida.The results from solution culture experiments reveals that compared to other treatments,the growth of cucumber seedlings is increased under the treatment of siderophore filtrate of strain A3 with 50 μmol/L FeCl3 in iron deficiency Hoagland solution,especially for shoot height,root length,leaf length,fresh mass and total leaf chlorophyll content.These may provide strong evidence that the siderophore produced by P.putida A3 is helpful to the growth promotion of cucumber seedlings under low iron conditions.%从大棚蔬菜根际土中分离到一株嗜铁素高产菌株A3,铬天青（CAS）法定量检测其嗜铁素相对含量达93.40%,Shenker＇s实验确定为羧酸型嗜铁素。在不同底物诱导下,该菌株可不同程度地产生吲哚乙酸（IAA）及1-氨基环丙烷-1-羧酸（ACC）脱氨酶,并具有一定的溶磷能力。根据形态特征、生理生化、API系统及16S rRNA基因序列分析,将菌株A3鉴定为恶臭假单胞菌（Pseudomonas putida）。在缺铁Hoagland营养液中添加难溶性铁及菌株A3嗜铁素发酵滤液的处理组,能够显著提高黄瓜幼苗的株高、根长、叶长、鲜重及叶绿素含量,表明菌株A3产生的嗜铁素在低铁条件下对黄瓜幼苗具有促生作用。
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