盐生植物碱蓬二型果实表生细菌的群落组成及促生属性

The community composition and growth-promoting activities of the cultivable epiphytic bacteria from the dimorphic fruits of Suaeda glauca Bunge

摘要:

【背景】碱蓬(Suaeda glauca Bunge)主要生长于含盐碱土壤，具有果实(种子)二型现象，而种子栖居有众多微生物，它们对种子萌发和幼苗建成具有重要影响。【目的】对碱蓬异型果实表生细菌的群落组成及相关细菌的促生属性进行观察研究，探讨不同类型果实表生细菌的群落组成及相关细菌的促生功能属性是否存在差异。【方法】利用纯培养方法对碱蓬二型果实的表生可培养细菌进行分离纯化，基于16S rRNA基因序列分析初步确定分离菌株的系统发育地位，并对获得菌株进行固氮、溶磷、解钾、产铁及产IAA能力的定性检测。【结果】碱蓬二型果实具有不同的表生细菌群落组成及分布比例，A型果实表生细菌分属于3纲15属，其优势属组成主要是短小杆菌属(34.33%)、芽孢杆菌属(13.43%)和泛菌属(10.45%)；B型果实表生细菌分属于4纲20属，其优势属组成主要是短小杆菌属(12.77%)、芽孢杆菌属(17.02%)和冰冻小杆菌属(14.89%)。碱蓬二型果实的表生细菌多样性指数也存在差异，A型果实的Shannon多样性指数、Margalef丰富度指数和Shannon均匀度指数显著低于B型果实；而A型果实的Berger-Parker优势度指数显著高于B型果实。碱蓬二型果实表生细菌在固氮、溶磷、解钾、产铁及产IAA能力等促生属性上的菌株分布比例存在不同变化趋势，A型和B型果实均具有较高比例固氮菌株及较低比例溶磷菌株；但在解钾菌株和产IAA菌株分布比例上具有不同变化趋势，A型果实的解钾菌株所占比例显著高于B型果实，而产IAA能力菌株所占比例显著低于B型果实。【结论】盐生植物碱蓬具有明显不同的2种类型果实，其不同类型果实具有不同的表生细菌群落组成及分布比例，且在促生功能菌株的分布上也存在不同变化趋势。

Abstract:

[Background] Seeds can harbor a lot of microorganisms and may influence a range of seed traits. The interactions between seed type and microorganisms are important for understanding seed germination and seedling growth. However, the interaction between different type seeds and seed-associated microorganisms in seed-heteromorphic plant is poor characterized. [Objective] To isolate and analyze community composition and growth-promoting activities of the epiphytic bacteria of two distinct types of fruits present on the same plant, Suaeda glauca Bunge., which mainly distributed in saline-alkaline soil. [Methods] Conventional culture dependent method was used to isolate the epiphytic bacteria from dimorphic fruits of S. glauca. The identification of the isolated strains was done based on 16S rRNA gene sequencing. The growth-promoting activities of isolated strains were also analyzed qualitatively. [Results] The epiphytic bacterial community composition of the type A fruits clearly differed from those of type B fruits. The results showed that, 67 epiphytic bacteria were isolated from type A fruits, which belonged to 3 classes, and 15 genus with Curtobacterium (34.33%), Bacillus (13.43%) and Pantoea (10.45%) as the most dominant genus; whereas 47 epiphytic bacteria were isolated from type B fruits, which belonged to 4 classes, 20 genus with Curtobacterium (12.77%), Bacillus (17.02%) and Frigoribacterium (14.89%) as the most dominant genus. The diversity of isolates were analyzed and compared using different diversity index, the shannon index, margalef index and evenness index which showed type A fruits were lower than those of type B fruits; but the Berger-Parker dominance index of type A fruits was higher than that of type B fruits. The percentage of the isolates with nitrogen-fixing, phosphate-solubilizing, potassium-dissolving, siderophore-producing and IAA-producing activity showed different changing trend in the dimorphic fruits of S. glauca. The high-proportioned nitrogen-fixing activity and the low-proportioned phosphate-solubilizing activity presented in strains which isolated from the type A and type B fruits of S. glauca. In addition, the percentage of potassium-dissolving activity in strains isolated from type A fruits showed higher than that of type B fruits, whilethe IAA-producing activity in strains isolated from type A fruits showed lower than that of type B fruits. [Conclusion] Our results show thatthe diversity, the community composition and growth-promoting activities of epiphytic bacterial communities in the dimorphic fruits of S. glauca arevaries.