基因组分析揭示Streptococcus thermophilus ND-07富产胞外多糖分子机制

Genomic insights into the high exopolysaccharides-producing bacterium Streptococcus thermophilus ND-07

Streptococcus thermophilus ND-07分离自青海地区自然发酵酸牦牛奶样品,通过与商业发酵剂菌株进行发酵特性的比较,发现Streptococcus thermophilus ND-07具有优良的发酵特性,特别是具有富产胞外多糖的能力。为了深入分析Streptococcus thermophilus ND-07富产胞外多糖的分子机制,本研究利用Pac Bio RS II三代测序平台完成了Streptococcus thermophilus ND-07全基因组测序。Streptococcus thermophilus ND-07基因组全长为1,869,510-bp,编码2,095个基因。比较基因组分析发现,Streptococcus thermophilus ND-07基因组含有一个20.5-kb的胞外多糖基因簇,其中包括两对决定胞外多糖链长度的eps C-epsD基因,表明Streptococcus thermophilus ND-07可以产生两种胞外多糖:荚膜多糖和黏液多糖。本研究在分子水平上揭示了Streptococcus thermophilus ND-07富产胞外多糖的机制,为Streptococcus thermophilus ND-07的工业化应用奠定了基础。

Streptococcus thermophilus ND-07 was isolated from naturally fermented yak milk in Qinghai, China. The excellent fermentation properties make the strain to be a potentially commercial dairy starter. The complete genome sequence was carried out using the PacBio RS Ⅱ platform. The genome contains a circular chromosome with 5 101 809 bp encoding 2 095 genes in total. The genomic study found two-pair epsC-epsD genes in a 20.5-kb exopolysaccharide gene cluster of the genome. Tfiis may indicate that Streptococcus thermophilus ND-07 can produce two types of exopolysaccharides： capsular and ropy exopolysaccharides. The genome information provide a genetic basis for understanding the excellent fermentation properties of Streptococcus thermophilus ND-07.