Identification of a Gene Cluster for the Biosynthesis of a Long, Galactose-Rich Exopolysaccharide in Lactobacillus rhamnosus GG and Functional Analysis of the Priming Glycosyltransferase
Identification of a Gene Cluster for the Biosynthesis of a Long, Galactose-Rich Exopolysaccharide in Lactobacillus rhamnosus GG and Functional Analysis of the Priming Glycosyltransferase
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DOI：
10.1128/aem.02919-08
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发表时间：
2009-06-01
影响因子：
4.4
通讯作者：
De Keersmaecker, Sigrid C. J.
中科院分区：
文献类型：
--
作者：
Lebeer, Sarah;Verhoeven, Tine L. A.;De Keersmaecker, Sigrid C. J.
细胞表面多糖在人类细菌病原体中作为毒力因子具有确定的作用。较少记载的是有益细菌中表面多糖的生物合成和生物学功能。我们确定了一个基因簇，编码酶和调节和转运蛋白的胞外多糖（EPS）的生物合成的不同步骤的记录良好的益生菌菌株鼠李糖乳杆菌GG。随后的welE基因突变，编码引发的糖基转移酶在这个集群，野生型与突变株的比较表型分析证实了该基因簇的生物合成的高分子量，富含半乳糖的杂聚EPS分子的特定功能。表型分析包括单体组成的测定，估计分离的EPS分子的聚合物长度，和表面多糖的单分子力谱。对welE突变体的进一步表征也表明，剥夺这些长的、富含半乳糖的EPS分子导致L. rhamnosus GG，可能是因为粘附素如菌毛样结构的屏蔽较少。
Cell surface polysaccharides have an established role as virulence factors in human bacterial pathogens. Less documented are the biosynthesis and biological functions of surface polysaccharides in beneficial bacteria. We identified a gene cluster that encodes the enzymes and regulatory and transporter proteins for the different steps in the biosynthesis of extracellular polysaccharides (EPS) of the well-documented probiotic strain Lactobacillus rhamnosus GG. Subsequent mutation of the welE gene, encoding the priming glycosyltransferase within this cluster, and comparative phenotypic analyses of wild-type versus mutant strains confirmed the specific function of this gene cluster in the biosynthesis of high-molecular-weight, galactose-rich heteropolymeric EPS molecules. The phenotypic analyses included monomer composition determination, estimation of the polymer length of the isolated EPS molecules, and single-molecule force spectroscopy of the surface polysaccharides. Further characterization of the welE mutant also showed that deprivation of these long, galactose-rich EPS molecules results in an increased adherence and biofilm formation capacity of L. rhamnosus GG, possibly because of less shielding of adhesins such as fimbria-like structures.