蒙古黄芪内生细菌产IAA菌株筛选与培养条件优化

Identification and selection of IAA-producing strains from endophytic bacteria of Astragalus membranaceus var. mongholicus root and optimization of culture conditions

摘要:

【目的】探寻蒙古黄芪内生菌的促生功能，挖掘优异微生物资源。【方法】采用前期从蒙古黄芪品系甘芪 1 号根中分离纯化的 20 株内生细菌菌株（B1~B20，GenBank 序列收录号 OM938262~OM938281）为研究对象，以纯培养液为对照（CK），利用 Salkowski 显色法对产吲哚乙酸 （IAA）功能菌株鉴定，然后对优异菌株的培养条件进一步进行优化研究。【结果】甘芪 1 号根可培养内生细菌菌株，有 12 株菌株较 CK 有明显 Salkowski 显色反应，测量各菌株产 IAA 浓度依次为 B16＞B18 ＞B10＞B20＞B8＞B13＞B11＞B3＞B4＞B6＞B1＞B17，产 IAA 浓度范围为 2. 74~26. 48 mg/L，平均 10. 10 mg/L，其中 B16 高稳产 IAA（GenBank OM938262），平均产 IAA 浓度高达 26. 48 mg/L，极显著高于其他菌株产 IAA 的水平。培养条件优化显示，B16 菌株培养最适温度为 15~25 ℃，在浓度为 0. 1%~7% 的 NaCl培养基均能正常生长，最适 NaCl浓度为 1%，最适 pH 为 7. 0，最适碳、氮源分别为酵母提取物和蛋白胨 。 培养条件优化后 B16 增殖及 IAA 产能较优化前分别极显著提高 28. 6% 和 53. 5%。【结论】蒙古黄芪根内生细菌中产 IAA 菌株比例较高，是优异豆科药用植物微生物资源宝库， 且筛选到一株高稳产 IAA 菌株 B16，经过培养条件优化可达到 40. 658 mg/L，是有较大的生态调控利用潜力的菌株。

Abstract:

【Objective】 To explore the growth promoting capabilities of its endophytic bacteria and harness excellent microbial resources.【Method】 We isolated and purified 20 endophytic bacterial strains （B1 ~B20，GenBank serial numbers OM938262~OM938281） from the roots of "Ganqi No. 1". Using a pure culture medium as control （CK），we identified functional strains capable of producing indoleacetic acid （IAA） through salkowski chromogenic method. Subsequently，we optimised the culture conditions for the outstanding strains.【Result】 The results showed that 12 strains of endophytic bacteria from the root of "Ganqi No. 1" exhibited significant Salkowski color reactions compared to CK. Among them，strain B16 demonstrated the highest IAA production concentration，followed by B18 > B10 > B20 > B8 > B13 > B11 > B3 > B4 > B6 > B1 > B17，respectively. The IAA production concentrations ranged from 2. 74 to 26. 48 mg/L，average 10. 10 mg/L. Notably，strain B16（GenBank OM 938262） consistently produced IAA at a high concentration of 26. 48 mg/L，significantly outperforming other strains. Optimization of culture conditions showed that strain B16 thrived in 0. 1%~7% NaCl medium at temperatures ranging 15 ℃ to 25 ℃，with the optimum NaCl concentration being 1% and the optimal pH level at 7. 0. Yeast extract and peptone were identified as the optimal carbon and nitrogen sources respectively. Following optimization process，strain B16 exhibited a 28. 6% increase in proliferation and a 53. 5% enhancement in IAA production.【Conclusion】 These findings highlight the prevalence of IAA‐producing strain among the endophytic bacteria of Astragalus mongholicus root，underscoring their importance as a valuable resource for medicinal leguminous plants. Strain B16，in particular，emerged as a highly stable producer of IAA with its production reaching 40. 658 mg/L postculture condition optimization. This strain holds significant potential for ecological regulation and utilization.