柽柳根际一株盐单胞菌Bachu 26的分离、鉴定及其盐胁迫下的促生作用研究

Isolation and identification of Halomonas sp. Bachu 26 with plant growth-promoting effect from rhizosphere of Tamarix chinensis under salt stress

摘要:

盐渍化是世界性的土壤问题，植物促生根际细菌（plant growth-promoting rhizobacteria，PGPR）在盐碱地改良和促进植物生长方面具有独特优势。柽柳是典型的盐生植物，筛选其根际微生物并研究其促生效果与促生机制，以此开发微生物菌肥，具有重要的应用价值。【目的】筛选耐盐碱植物柽柳的根际微生物，对其基本特性、耐盐碱能力、促生功能及促生效果进行评估。【方法】从新疆巴楚境内野生柽柳根际土壤中筛选出一株耐盐碱细菌菌株Bachu 26；通过形态学观察、生理生化特性测定和16S rRNA基因序列分析，对该菌株进行鉴定；利用不同盐浓度（0%–20%）和不同pH （7.0–13.0），对菌株Bachu 26的耐盐耐碱能力进行测定；采用多种功能鉴定培养基测定其促生功能，并对生长素吲哚乙酸（indole-3-acetic acid，IAA）进行定量测定；通过二分格培养皿实验验证菌株产生挥发性酸性物质的能力；在普通培养皿上将拟南芥幼苗与菌株Bachu 26共培养，分析菌株对拟南芥幼苗的促生作用；在二分格培养皿上将拟南芥与Bachu 26隔离培养，分析菌株产生的挥发性酸性物质对拟南芥幼苗的促生作用；用盆栽法分析该菌株对玉米幼苗的促生作用。【结果】菌株Bachu 26为盐单胞菌属（Halomonas），将其命名为Halomonas sp.Bachu 26，该菌株生长最高耐受盐浓度达20%，耐受的最高pH值为11.0。菌株Bachu 26具有溶解有机磷、固氮、产1-氨基环丙烷-1-羧酸脱氨酶（1-aminocyclopropane-1-carboxylicacid deaminase，ACC）、IAA和挥发性酸性物质的能力，其中IAA产量可达45.885 6 mg/L。菌株Bachu 26可显著提高拟南芥幼苗在盐碱胁迫条件下的鲜重、侧根数、主根长和叶片数；盆栽实验中可显著提高玉米在盐碱胁迫下的地上鲜重、地下鲜重和株高。【结论】新分离Bachu 26具有显著的耐盐碱促生效果，为后期盐碱地的改良和耐盐碱促生微生物肥料的开发提供了材料和理论支持，同时可以促进对盐单胞菌的应用和基础研究。

Abstract:

Salinization is a global soil problem. Plant growth-promoting rhizobacteria (PGPR) have unique advantages in remediating saline-alkali soils and promoting plant growth. Screening the rhizosphere microorganisms of Tamarix chinensis, a typical halophyte, and revealing the growth-promoting effect and mechanism of these microorganisms are of great significance for developing microbial fertilizers. [Objective] To screen out the microorganisms from the rhizosphere soil of saline-alkaline tolerant T. chinensis and measure their basic characteristics, salt and alkali tolerance, and plant growth-promoting effects. [Methods] A saline-alkali tolerant strain Bachu 26 was screened out from the rhizosphere soil of wild T. chinensis in Bachu, Xinjiang and identified based on the morphological, physiological, and biochemical characteristics and 16S rRNA gene sequence. We cultured the strain Bachu 26 in the media with different salt concentrations (0%-20%) and pH values (7.0-13.0) to evaluate its salt and alkali tolerance. We then used multiple functional media to examine the growth-promoting function of Bachu 26 and measured the production of indole-3-acetic acid (IAA). The petri dishes with two compartments were used to verify the ability of Bachu 26 to produce acidic volatile substances. Arabidopsis thaliana seedlings were co-cultured with strain Bachu 26 in common culture dishes, based on which the growth-promoting effect of Bachu 26 on A. thaliana seedlings was analyzed. Furthermore, A. thaliana seedlings and Bachu 26 were cultured dividually in the petri dishes with two compartments, based on which the growth-promoting effect of volatile acidic substances produced by Bachu 26 on the seedlings was analyzed. The growth-promoting effect of Bachu 26 on maize seedlings was analyzed by pot experiments. [Results] Strain Bachu 26 was identified as a species of Halomonas and named Halomonas sp. Bachu 26, with the maximum tolerance to 20% salt and pH 11.0. Halomonas sp. Bachu 26 could solubilize organic phosphorus, fix nitrogen, and produce ACC deaminase, IAA, and volatile acidic substances, with the IAA yield reaching 45.885 6 mg/L. Halomonas sp. Bachu 26 significantly increased the fresh weight, lateral roots, taproot length, and leaves of A. thaliana seedlings under saline-alkali stress. In pot experiments, Halomonas sp. Bachu 26 significantly increased the fresh weight of aboveground part, fresh weight of underground part, and plant height of maize under saline-alkali stress. [Conclusion] The newly isolated PGPR strain Bachu 26 has a significant plant growth-promoting effect. The findings provide material and theoretical support for the remediation of saline-alkali soil and development of saline-alkali tolerant plant growth-promoting microbial fertilizers. Furthermore, the results will promote the applied and basic research on Halomonas.