Using a nitrogen-free media, 232 bacteria were isolated from 50 soil samples collected in the provinces East Azerbaijan, Gilan and Ardabil in North of Iran. Plant growth-promoting traits of selected isolates were assessed under in vitro conditions. Moreover, PCR–RFLP analysis of the 16S rDNA and nifH genes was applied to investigate their genetic diversity. Forty percent of the bacteria were able to produce siderophores and the isolate 36A-2 (Pseudomonas) was identified as the best siderophore producer. All bacteria showed a much better phosphate solubilizing capacity with tricalcium phosphate than with rock phosphate as the phosphate source. The bacterial isolate 23A-6 (Pseudomonas) was observed to be the best phosphate solubilizers in the presence of tricalcium phosphate and 34SPIII (Pseudomonas) in the presence of rock phosphate. A K releasing capacity was shown for the bacterial isolates 36A-2 (Pseudomonas), 44SP-2 (Azotobacter chroococcum), 14SPIII (Achromobacter), 14SP2-1 (Azotobacter chroococcum) and 14A-4 (Agrobacterium). However, for most of the bacteria no K releasing ability was observed. The best IAA producer in the presence of 100 mg L⁻¹ L-tryptophan (12.26 mg L⁻¹) was found to be the bacterial isolate 23A-6 (Pseudomonas). Molecular and biochemical identification revealed that the isolates included in the study belong to the genera Azotobacter, Beijerinckia, Klebsiella, Pseudomonas, Rhizobium, Agrobacterium, Achromobacter, Stenotrophomonas and Sphingomonas. The Azotobacteria included in the study were all identified as A. chroococcum. With the exception of the isolate 35A-2, all of them produced the same PCR–RFLP pattern with the 16S rDNA and nifH PCR products. The bacterial isolates 23A-6, 34SPIII and 36A-2 (Pseudomonas) were identified as promising candidates to be used as plant growth-promoting bacteria.

使用无氮培养基，从伊朗北部东阿塞拜疆省、吉兰省和阿尔达比勒省收集的 50 个土壤样本中分离出 232 种细菌。在体外条件下评估所选分离株的植物生长促进性状。此外，应用 16S rDNA 和nifH基因的 PCR-RFLP 分析来研究它们的遗传多样性。40% 的细菌能够产生铁载体，分离株 36A-2（假单胞菌）被确定为最好的铁载体生产者。所有细菌都表现出用磷酸三钙比用磷酸岩作为磷酸盐源更好的磷酸盐溶解能力。细菌分离物 23A-6（假单胞菌属) 被观察到在磷酸三钙和 34SPIII（假单胞菌）存在下在磷酸岩存在下是最好的磷酸盐增溶剂。对于细菌分离株 36A-2（假单胞菌属）、44SP-2（浅色固氮菌）、14SPIII（无色杆菌）、14SP2-1（浅色固氮菌）和 14A-4（农杆菌）显示了 AK 释放能力。然而，对于大多数细菌，没有观察到 K 释放能力。发现存在 100 mg L ^-1 L-色氨酸 (12.26 mg L ^-1 ) 的最佳 IAA 生产者是细菌分离物 23A-6 (假单胞菌属）。分子和生化鉴定结果表明，本研究纳入的分离菌属于固氮菌属、拜耶林克菌属、克雷伯菌属、假单胞菌属、根瘤菌属、农杆菌属、无色杆菌属、窄食单胞菌属和鞘氨醇单胞菌属。研究中包括的固氮菌都被确定为A. chroococcum。除了分离株 35A-2 外，它们都产生了与 16S rDNA 和nifH PCR 产物相同的 PCR-RFLP 模式。细菌分离物 23A-6、34SPII 和 36A-2（假单胞菌) 被确定为有希望用作植物生长促进细菌的候选物。