耐盐促生菌的分离鉴定及其对设施次生盐渍化土壤的改良效果

Isolation and identification of salt-tolerant growth-promoting bacteria capable of remediating secondary salinized soils of greenhouses

摘要:

【背景】 土壤次生盐渍化现象非常普遍，严重制约了设施蔬菜产业的可持续发展。【目的】 筛选耐盐促生微生物菌株，为设施次生盐渍土壤改良提供菌种资源。【方法】 采用稀释涂平板法在含盐量5%的LB培养基上进行盐渍化土壤样品中耐盐菌株的筛选；采用浸种法筛选具有促生作用的耐盐菌株；采用形态学、生理生化和16S rRNA基因序列分析对耐盐促生菌进行分类鉴定；采用定性和定量分析法确定菌株的耐盐促生性质；采用盆栽试验评价耐盐促生菌株对设施土壤修复及黄瓜生长的效果。【结果】 从采集的37份设施盐渍化土壤样品中分离获得58株耐盐细菌，其中5株菌对黄瓜简化活力指数增长率大于15%，并且在0.3%的NaCl浓度下均对黄瓜幼苗具有一定的促生长作用，但是随着NaCl浓度升高其促生能力下降。经鉴定菌株YQ-1-8为贝莱斯芽孢杆菌(Bacillus velezensis)、菌株SN-1-4为干旱节杆菌(Arthrobacter arilaiti)、菌株3A-2为黄海芽孢杆菌(B. marisflavi)、菌株L1-2为蜡样芽孢杆菌(B. cereus)、菌株L3-3为阿氏芽孢杆菌(B. aryabhattai)，其中菌株3A-2具有解有机磷、产吲哚-3-乙酸(indole-3-acetic acid, IAA)和产胞外多糖的性质。土壤中菌株3A-2浓度为1×10⁷ cfu/g时对黄瓜幼苗有明显的促生作用，茎粗、株高、地上部鲜重、地上部干重和叶绿素分别较对照增加12.39%、14.31%、30.92%、38.46%和9.06%，并且显著增加土壤碱解氮和速效钾含量，降低土壤pH、电导率和全盐含量(P<0.05)。【结论】 菌株3A-2兼具耐盐促生作用，能够用于盐渍化土壤的改良，为次生盐渍土壤微生物改良产品的研制提供菌株资源。

Abstract:

[Background] The prevalence of secondary salinization in soil poses a significant constraint on the sustainable development of protected vegetable production. [Objective] To screen out the salt-tolerant growth-promoting microbial strains and provide bacterial resources for remediating secondary salinized soils in greenhouses. [Methods] The LB medium with 5% salt was used to screen out the salt-tolerant strains from the soil samples of vegetable greenhouses by the dilution-plate coating method. The growth-promoting ability of each strain was determined by the seed immersion method. The morphological characteristics, physiological and biochemical properties, and 16S rRNA gene sequence were used to identify the strains. The salt tolerance and growth-promoting effect of each strain were measured by quantitative and qualitative methods. Pot experiments were carried out to examine the remediation effect of each strain on salinized soil samples and the cucumber growth-promoting effect. [Results] Fifty-eight strains of salt-tolerant bacteria were isolated from 37 salinized soil samples. Among them, five strains, YQ-1-8, SN-1-4, 3A-2, L1-2, and L3-3, increased the simplified activity index of cucumber by more than 15%, and all of them had growth-promoting effects on cucumber seedlings exposed to 0.3% salt. However, the growth-promoting effect decreased with the increasement of the salt concentration. YQ-1-8 was identified as B acillus velezensis, SN-1-4 as Arthrobacter arilaiti, 3A-2 as B. marisflavi, L1-2 as B. cereus, and L3-3 as B. aryabhattai. Strain 3A-2 was capable of solubilizing organophosphorus and producing IAA and exopolysaccharide. The results of pot experiments showed that 3A-2 at 1×10⁷ cfu/g increased the stem thickness, plant height, aboveground fresh weight, aboveground dry weight, and chlorophyll by 12.39%, 14.31%, 30.92%, 38.46%, and 9.06%, respectively. In addition, the strain increased the content of available nitrogen and available potassium and decreased the pH, electrical conductivity, and total salt content in soil (P<0.05). [Conclusion] Strain 3A-2 with salt tolerance and growth-promoting effect can serve as a candidate for the development of microbial agents for the recommendation of secondary salinized soils.