产铁载体菌株的分离、培养条件优化及初步应用

Isolation,culture condition optimization,and preliminary application of siderophore-producing strains

摘要:

【背景】微生物菌肥是推动绿色农业发展的关键。铁载体是由植物根际微生物产生的 一类低分子量金属离子螯合物，可通过螯合Fe³⁺促进植物生长，因此，筛选具有高产铁载体功能的菌种意义重大。【目的】从植株根际土壤中分离高产铁载体微生物，为开发植物根际促生菌提供种质资源。【方法】采用chrome azurol sulfonate (CAS)平板覆盖法分离、纯化获得高产铁载体真菌菌株，通过形态观察及18S rRNA基因序列分析对菌株进行鉴定，在此基础上，采用单因素实验法优化其产铁载体条件，并通过上海青水培试验，初步考察菌株的促生效应。【结果】分离获得 4株产铁载体真菌菌株，其中一株菌产铁载体能力相对较强，编号为RL1，初步鉴定为黑曲霉(Aspergillus niger)。RL1的最佳产铁载体培养条件为：初始pH 5.0，碳源葡萄糖含量5 g/L，温度20 ℃，培养时间5 d，转速60 r/min。随着RL1菌悬液浓度的增加，上海青植株的鲜重和叶片光合色素含量均逐渐增大。当施加最大浓度孢子菌悬液(3.2×10⁸ CFU/mL)时，植株的总鲜重量和茎叶鲜重量增幅分别为75.0%和74.4%，叶绿素a、叶绿素b和类胡萝卜素含量增幅分别为49.8%、70.9%和26.7%。【结论】本研究分离获得一株高产铁载体真菌菌株RL1，优化后的培养条件更利于菌株铁载体的合成，而且该菌株能够有效促进上海青幼苗的生长。

Abstract:

[Background] The key to promoting green agriculture is microbial fertilizer.Siderophore is a low molecular iron chelate produced by rhizosphere microorganisms,which can promote plant growth by chelating Fe³⁺.Therefore,it is of great significance to screen out the strains with high-yield siderophore.[Objective] In order to provide germplasm resources for the development of plant growth-promoting bacteria,we isolated high-yielding siderophore microorganisms from rhizosphere soil.[Methods] A fungal strain with high yield of siderophore was isolated and purified by chrome azurol sulfonate (CAS) overlay plate method.The strain was identified based on morphological observation and 18S rRNA gene analysis.The culture conditions for siderophore production were optimized by single factor experiment,and the growth-promoting effect of the strain was preliminarily investigated by hydroponic experiment of Chinese cabbage.[Results] Four strains of siderophore-producing fungi were isolated,one of which with strong siderophores-producing ability was numbered RL1 and preliminarily identified as Aspergillus niger.The optimal culture conditions for siderophore production of strain RL1 were as follows:initial pH 5.0,carbon source of glucose at 5 g/L,temperature at 20℃,culture time of 5 days,and rotational speed of 60 r/min.The fresh weight and photosynthetic pigment content of Chinese cabbage increased with the increase in the concentration of RL1 suspension.When the maximum concentration (3.2×10⁸ CFU/mL) of suspension was applied,the total fresh weight and the aboveground weight of Chinese cabbage increased by 75.0% and 74.4%,respectively,and the content of chlorophyll a,chlorophyll b,and carotenoid increased by 49.8%,70.9% and 26.7%,respectively.[Conclusion]In this study,a fungal strain RL1 with high-yield siderophore was isolated.High siderophore production of the strain was achieved at optimized culture conditions,and the strain could effectively promote the growth of Chinese cabbage seedlings.