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

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.

Key words:Nitrogen-fixing bacteria, Klebsiella variicola, gene sequence, exopolysaccharide, protein, structural characteristic