固氮菌Klebsiella variicola GN02基因序列及其分泌胞外多糖的相关特性

Gene sequence of nitrogen-fixing bacteria Klebsiella variicola GN02 and its association with exopolysaccharide secretion

摘要:

【背景】一些固氮菌能分泌胞外多糖，与宿主植物的关系密切，在提供氮素和促进植物生长有重要作用。【目的】进行固氮菌Klebsiella variicola GN02的基因序列分析，了解分泌胞外多糖的相关基因和其蛋白的结构特性。【方法】用二代和三代测序技术相结合的方法对GN02菌株进行全基因组分析，并对其分泌的胞外多糖进行理化、结构特性解析。【结果】GN02菌株基因组中含有许多与氮代谢及多糖合成、分泌相关的基因及蛋白，该菌株培养后提取的胞外多糖得率为6.90 g/L、分子量1.8×103 Da、比旋度[α]25D75°、粘度[η] 80.28；多糖组成为葡萄糖、半乳糖和甘露糖，为(1→3)及(1→6)糖苷键连接的β构型多糖，具有多糖的红外光谱特征吸收峰。【结论】提供了K. variicola GN02菌株基因组序列，解析了分泌胞外多糖的基因相关蛋白、理化性质及结构特性，有助于进一步了解该固氮菌分泌多糖的机理及为植物促生作用的相关性研究提供基础。

Abstract:

[Background] Some nitrogen-fixing bacteria can secrete exopolysaccharide, which was closely related to the host plants, and plays an important role in providing nitrogen and promoting the growth of plants. [Objective] To analyze the gene sequence of nitrogen-fixing bacteria Klebsiella variicola GN02, and the structural characteristics of the genes and proteins relating to the secretion of extracellular polysaccharides were investigated. [Methods] The whole genome of GN02 strain was analyzed by the combination of the second and third-generation sequencing techniques, and the physicochemical and structural characteristics of its secreted extracellular polysaccharides were also analyzed. [Results] The genome of GN02 strain contains many genes and proteins relating to nitrogen metabolism and polysaccharide synthesis and secretion. The yield of exopolysaccharide extracted by GN02 strain was 6.90 g/L, molecular weight was 1.8×103 Da, specific rotation [α] 25D 75° and the viscosity [η] was 80.28. The polysaccharides consist of glucose, galactose and mannose, which were β-configuration polysaccharides linked by (1→3) and (1→6) glycoside bonds, and had the characteristic absorption peak in infrared spectrum. [Conclusion] The genomic sequence of K. variicola GN02 strain was provided, and the gene-relating proteins, physicochemical properties and structural properties of extracellular polysaccharides were analyzed, which helped to further understand the mechanism of exopolysaccharides secreted by nitrogen-fixing bacteria and to provide the basis for the correlation research of plant growth promoting effect.