一株嗜盐嗜碱菌属促生菌的分离及功能鉴定

Isolation and functional identification of a growth-promoting rhizobacterial strain of Alkalibacterium

摘要:

【背景】土壤盐碱化是一个全球性问题，耐盐植物根际存在大量未被开发的功能微生物，例如植物根际促生菌(plant growth-promoting rhizobacteria, PGPR)。这些微生物能够通过自身的促生功能帮助植物抵抗盐碱胁迫并促进植物生长。【目的】筛选出具有耐盐碱作用的PGPR，研究其促生功能，为研发盐碱地专用功能性微生物肥料提供候选菌株。【方法】从新疆维吾尔自治区喀什地区野生柽柳根际土壤中筛选出一株耐盐碱细菌Bachu49；通过形态学、生理生化特性和16S rRNA基因测序技术对其进行分类鉴定；利用多种功能鉴定培养基测定菌株Bachu49的解钾、固氮、解磷、吲哚乙酸合成、1-氨基环丙烷-1-羧酸(1-aminocyclopropane-1-carboxylate, ACC)脱氨酶和铁载体合成等促生能力；采用二分格培养皿验证菌株Bachu49产生挥发性酸性物质的能力；最后分别通过平皿和盆栽试验测定菌株对拟南芥和玉米幼苗生长的影响。【结果】从供试土壤样品中筛选分离到一株耐盐碱菌株Bachu49，经16S rRNA基因序列比对分析鉴定为嗜盐嗜碱菌属(Alkalibacterium)；菌株Bachu49拥有固氮、解有机磷和分泌吲哚乙酸(indole-3-acetic acid，IAA)等促生能力，可在盐浓度0−160 g/L、pH 7.0−11.0的条件下生长，该菌还具有一定的降碱能力。在pH 8.0、9.0和10.0的条件下，降碱率分别为9.75%、15.56%和20.60%。促生试验结果表明菌株Bachu49可以显著促进拟南芥、玉米在盐碱胁迫条件下的生长。其中，在pH 8.0、2 mmol/L NaHCO₃的盐碱胁迫条件下，接种了菌株Bachu49后拟南芥的根长、侧根数目、鲜重和叶片数分别增加了239.86%、1 952.83%、389.71%和91.23%；在15 g/kg的盐胁迫条件下，玉米的地下鲜重增加了10.14%，而在30 g/kg的盐碱胁迫条件下，玉米的地上鲜重、茎粗和株高分别增加了42.04%、23.14%和40.91%。【结论】Alkalibacterium sp. Bachu49具有优良的耐盐碱与促生能力，能够显著促进植物在盐碱胁迫下的生长，这为今后在研发盐碱地专用功能型微生物肥料方面提供了菌种资源和理论基础。

Abstract:

[Background] Soil salinization is a global problem, and there are a large number of undeveloped functional microorganisms in the rhizosphere of salt tolerant plants, such as plant growth-promoting rhizobacteria (PGPR). These microorganisms can help plants resist salt alkali stress and promote plant growth through their own growth promoting functions. [Objective] This study screened plant growth-promoting rhizobacteria (PGPR) with salt-alkali tolerance and evaluated their growth-promoting effects, aiming to provide candidate strains for the development of microbial fertilizers for saline-alkaline land. [Methods] A bacterial strain Bachu49 with salt-alkali tolerance was isolated from the rhizosphere soil of wild Tamarix chinensis in Kashgar Prefecture of Xinjiang. This strain Bachu49was identified based on morphological, physiological, and biochemical characteristics and 16S rRNA gene sequence. Multiple media for functional identification were used to examine the growth-promoting effects [solubilizing potassium, fixing nitrogen, solubilizing phosphorus, synthesizing indole-3-acetic acid (IAA), secreting 1-aminocyclopropane-1-carboxylate (ACC) deaminase, and producing siderophores] of Bachu49. The Petri dish with two compartments was used to examine the production of volatile acid substances by Bachu49. Finally, the effects of Bachu49 on the growth of Arabidopsis and maize seedlings were analyzed by plate and pot experiments, respectively. [Results] A strain Bachu49 with salt-alkali tolerance was isolated from the soil samples. This strain was identified as Alkalibacterium sp. and named Alkalibacterium sp. Bachu49. Strain Bachu49 had the effects of fixing nitrogen, solubilizing organic phosphorus, and synthesizing IAA. It survived within the salt concentration of 0−160 g/L and pH 7.0−11.0 and showed the ability of reducing alkali. At pH 8.0, 9.0, and 10.0, the alkali reduction rates of Bachu49 were 9.75%, 15.56%, and 20.60%, respectively. Strain Bachu49 promoted the growth of Arabidopsis and maize seedlings under salt-alkali stress. Specifically, at pH 8.0 and 2 mmol/L NaHCO₃, inoculation with strain Bachu49 increased the root length, number of lateral roots, fresh weight, and number of leaves of Arabidopsis by 239.86%, 1 952.83%, 389.71%, and 91.23%, respectively. Inoculation of this strain increased the underground fresh weight of maize seedlings by 10.14% in the presence of 15 g/kg salt-alkali, and it increased the aboveground fresh weight, stem diameter, and plant height of maize seedlings by 42.04%, 23.14%, and 40.91%, respectively, under 30 g/kg salt-alkali stress. [Conclusion] Alkalibacterium sp. Bachu49 has excellent salt-alkali tolerance and plant-growth promoting effects under salt-alkali stress. This study provides a candidate strain and a theoretical basis for the future development of specialized microbial fertilizers for saline-alkali soil.