广西葛根内生细菌的分离鉴定及其促生特性

Endophytic bacteria from Pueraria montana var. lobata in Guangxi: isolation, identification, and characterization of plant growth-promoting effect

摘要:

【背景】植物内生菌长期与宿主共生，对宿主生长发育产生影响。葛根作为重要的药食两用作物，葛根内生菌的研究具有重要实践意义。【目的】对广西葛根根部内生细菌进行分离、鉴定及促植物生长特性分析，旨在了解该药食同源植物内生细菌种群结构及其促生特性，为分析内生菌群体在药食同源植物产量和品质形成的作用及其内生细菌资源的开发利用提供参考。【方法】采用6种不同的培养基从广西葛根的根瘤、根系和根愈伤组织分离内生细菌，16S rRNA基因测序和系统发育分析内生细菌的分布特征和遗传多样性，采用生理生化方法测定分离菌株的固氮活性、溶磷特性、产生嗜铁素、分泌吲哚乙酸(indole-3-acetic acid, IAA)等促生特性。【结果】从葛根根瘤、根系和根部愈伤组织中共分离得到223个菌株，16S rRNA基因测序鉴定这些菌株隶属于2门4纲10科19属，其中芽孢杆菌属、假单胞菌属、土壤杆菌属、肠杆菌属为葛根优势菌群；内生细菌数量和群落组成存在明显的组织特异性，其数量表现为根瘤>根系>根愈伤组织，但其种群多样性表现为根愈伤组织>根系>根瘤。不同培养基分离出的细菌种群丰富度有差异。从供试菌株中筛选出6株具有nifH基因的内生菌，15株兼具固氮、溶磷、产生嗜铁素、分泌IAA 4种促生特性的内生菌，17株兼具3种促生特性的内生菌。【结论】广西葛根内生细菌资源非常丰富，内生菌在葛根体内分布具有明显的组织特异性，兼具多种促生特性。

Abstract:

[Background] Endophytic bacteria coexist with the host for a long time, posing an impact on the growth and development of the host. Pueraria montana is an important plant with both medicinal and edible values. The research on the endophytic bacteria of this plant is of practical significance. [Objective] To isolate and identify the endophytic bacteria from the roots of Pueraria. montana var. lobata growing in Guangxi and analyze their growth-promoting effect, so as to learn the community structure and growth-promoting effects of endophytic bacteria from the medicinal and edible plants, and provide references for revealing the role of endophytic bacteria in the production and quality formation of medicinal and edible plants and the development and utilization of endophytic bacterial resources. [Methods] Six different media were used to isolate the endophytic bacterial strains from the root nodules, root system, and root callus of Pueraria montana var. lobata. The 16S rRNA gene sequencing was employed to explore the distribution characteristics and genetic diversity of the endophytic bacteria. The physiological and biochemical tests were carried out to determine the nitrogen-fixing activity, phosphorous-solubilizing properties, siderophore production, and indole acetic acid (IAA) secretion of the isolated strains. [Results] A total of 223 strains were isolated from the root nodules, root system, and root callus of Pueraria montana var. lobata. These isolates were phylogenetically classified into 19 genera, 10 families, 4 classes of 2 phyla based on their 16S rRNA gene sequences. Bacillus, Pseudomonas, Agrobacterium, Enterobacter were the predominant taxa. The number and community structure of the endophytic bacteria varied between tissues. Specifically, the number of the endophytic bacteria was in the order of root nodules>root system>root callus and the diversity in the order of root callus>root system>root nodules. Furthermore, the bacterial communities were also distinct from various culture media showed different richness. There were 6 strains with nifH gene, 15 strains with four growth-promoting properties including nitrogen fixation, phosphorous solubilizing, siderophore production, and IAA secretion, and 17 strains with three growth-promoting properties were selected from the tested strains. [Conclusion] The endophytic bacteria in the roots of Pueraria montana var. lobata from Guangxi are genetically diverse, with the distribution varying between tissues and multiple growth-promoting properties.