Comparative genomic analysis of Lactobacillus rhamnosus GG reveals pili containing a human-mucus binding protein
Comparative genomic analysis of Lactobacillus rhamnosus GG reveals pili containing a human-mucus binding protein
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DOI：
10.1073/pnas.0908876106
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发表时间：
2009-10-06
影响因子：
11.1
通讯作者：
de Vos, Willem M.
中科院分区：
文献类型：
--
作者：
Kankainen, Matti;Paulin, Lars;de Vos, Willem M.
为了阐明广泛使用的益生菌鼠李糖乳杆菌GG的生物学功能，我们将其3.0-Mbp的基因组序列与相似大小的L. rhamnosus LC 705，一种表现出与粘液结合减少的辅助起子培养物。两个基因组表现出高度的序列同一性和同线性。然而，对于这两个菌株，基因组岛，5在GG和4在LC 705，打断共线性。在这些岛屿中预测了大量的菌株特异性基因（GG中80个，LC 705中72个）。GG特异性岛包括编码噬菌体组分、糖代谢和运输以及胞外多糖生物合成的基因。一个岛只有在L。鼠李糖酵母GG含有3种分泌型LPXTG样菌毛蛋白（spaCBA）和一种菌毛蛋白专用分选酶的基因。使用抗SpaC抗体，通过免疫印迹证实细胞壁结合的皮利的物理存在。免疫金电子显微镜显示，SpaC菌毛蛋白位于菌毛尖端，但也零星的整个结构。此外，菌株GG对人肠粘液的粘附被SpaC抗血清阻断，并在携带失活的spaC基因的突变体中被废除。类似地，证明了纯化的SpaC蛋白与粘液的结合。我们的结论是，SpaC的存在是必不可少的粘液相互作用的L。rhamnosusGG，并可能解释其在干预试验期间在人肠道中持续时间长于LC 705的能力。非致病性革兰氏阳性细菌菌株表面上粘液结合皮利的存在揭示了所选益生乳酸杆菌与宿主组织相互作用的先前未描述的机制。
To unravel the biological function of the widely used probiotic bacterium Lactobacillus rhamnosus GG, we compared its 3.0-Mbp genome sequence with the similarly sized genome of L. rhamnosus LC705, an adjunct starter culture exhibiting reduced binding to mucus. Both genomes demonstrated high sequence identity and synteny. However, for both strains, genomic islands, 5 in GG and 4 in LC705, punctuated the colinearity. A significant number of strain-specific genes were predicted in these islands (80 in GG and 72 in LC705). The GG-specific islands included genes coding for bacteriophage components, sugar metabolism and transport, and exopolysaccharide biosynthesis. One island only found in L. rhamnosus GG contained genes for 3 secreted LPXTG-like pilins (spaCBA) and a pilin-dedicated sortase. Using anti-SpaC antibodies, the physical presence of cell wall-bound pili was confirmed by immunoblotting. Immunogold electron microscopy showed that the SpaC pilin is located at the pilus tip but also sporadically throughout the structure. Moreover, the adherence of strain GG to human intestinal mucus was blocked by SpaC antiserum and abolished in a mutant carrying an inactivated spaC gene. Similarly, binding to mucus was demonstrated for the purified SpaC protein. We conclude that the presence of SpaC is essential for the mucus interaction of L. rhamnosus GG and likely explains its ability to persist in the human intestinal tract longer than LC705 during an intervention trial. The presence of mucus-binding pili on the surface of a nonpathogenic Gram-positive bacterial strain reveals a previously undescribed mechanism for the interaction of selected probiotic lactobacilli with host tissues.