一株产胞外多糖的山药内生细菌Lysinibacillus fusiformis S-1的分离和鉴定

Isolation and identification of an exopolysaccharide producingIsolation and identi cation of an exopolysaccharide producing endophytic strain Lysinibacillus fusiformis S-1

微生物的胞外多糖是重要的生物资源,为获得新型的具有药用价值的胞外多糖产生菌,从山药、地瓜、马铃薯和胡萝卜的根茎组织中分离、筛选到11株能产胞外多糖的植物内生菌,利用苯酚–硫酸法对这11株菌的多糖产量进行了定量分析.对多糖产量最高的S-1菌株,检测其在发酵过程中菌体生长、胞外多糖生成以及发酵过程的pH变化,绘制其胞外多糖发酵代谢曲线.通过形态观察、培养特性观察、生理生化实验和16S rDNA序列分析对该菌株进行了鉴定.结果显示,S-1菌株在产糖培养基中可以产生1.50 g/L的胞外多糖,在11株菌中产量最高.16S rDNA序列分析显示该菌属于赖氨酸芽孢杆菌(Lysinibacillus),且与纺锤形赖氨酸芽孢杆菌(L.fusiformis)亲缘最近.综合其形态特征、培养特性和生理生化实验结果,将S-1菌株鉴定为纺锤形赖氨酸芽孢杆菌.该菌在胞外多糖产生菌中少有报道,为胞外多糖的进一步研究提供了菌种资源.

For a deeper understanding of the endophytic strains producing exopolysaccharide （EPS）, new strains of this type are needed to be isolated. This paper aimed to screen endophytic strains with medicinal value, and find bacteria resources for further study. Eleven endophytic strains producing EPS were isolated from Chinese yam, pachyrhizus, potato and carrot. And their EPS yields were analyzed by phenol-sulfuric acid method. Moreover, the fermentation curve of strain S-1, with the highest amount of EPS, was drafted by detection of biomass, pH and EPS production during its growing process. The strain S-1 was identified with methods of scanning electron microscopy （SEM）, cultural characteristics, physiological and biochemical analysis and 16S rDNA sequence analysis. With the analysis of polysaccharide yield, the highest amount of EPS of 1.50 g/L was acquired from strain S-1. Phylogenetic analysis of 16S rDNA gene sequence showed that strain S-1 belonged to the genus Lysinibacillus, with its closest relatives being Lysinibacillus fusiformis.