Identification of a functional capsule locus in Streptococcus mitis
Identification of a functional capsule locus in Streptococcus mitis
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DOI：
10.1111/j.2041-1014.2011.00635.x
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发表时间：
2012-04-01
影响因子：
3.7
通讯作者：
Petersen, F. C.
中科院分区：
文献类型：
--
作者：
Rukke, H. V.;Hegna, I. K.;Petersen, F. C.
肺炎链球菌的多糖荚膜是人类毒力的标志。在其近亲缓症链球菌（一种常见的人类链球菌）中，对6种菌株的测序基因组进行分析，发现其中4种菌株存在推定的荚膜位点。我们构建了一个类似于缓症链球菌的等基因突变体，该突变体来自模式菌株，该菌株在荚膜位点缺少19个开放阅读框（？cps突变体），使用类似于先前在类似于肺炎链球菌中的荚膜功能研究的缺失策略。透射电子显微镜和原子力显微镜揭示了一个类似于缓症型菌株的S.胶囊状结构，在？cps突变体。由于与缓症链球菌相似的链球菌是牙齿表面的主要口腔定殖者，因此我们解决了与缓症链球菌相似的链球菌的胶囊位点的相关性，包括整体表面性质、自动聚集和生物膜形成。胶囊删除导致突变体的疏水性增加约2倍。结合到所有的阳离子染料减少了40%，这表明在整体的突变体的表面负电荷的减少。该突变体还表现出增加的自聚集在共聚集缓冲液中，和高达六倍的生物膜水平的增加。结果表明，胶囊位点与类似于缓症链球菌的胶囊样结构的产生相关，并表明类似于缓症链球菌的胶囊样结构可能赋予与类似于肺炎链球菌的胶囊相关的表面属性相似的表面属性。
The polysaccharide capsule of Streptococcus pneumoniae is a hallmark for virulence in humans. In its close relative Streptococcus mitis, a common human commensal, analysis of the sequenced genomes of six strains revealed the presence of a putative capsule locus in four of them. We constructed an isogenic S.similar to mitis mutant from the type strain that lacked the 19 open reading frames in the capsule locus (?cps mutant), using a deletion strategy similar to previous capsule functional studies in S.similar to pneumoniae. Transmission electron microscopy and atomic force microscopy revealed a capsule-like structure in the S.similar to mitis type strain that was absent or reduced in the ?cps mutant. Since S.similar to mitis are predominant oral colonizers of tooth surfaces, we addressed the relevance of the capsule locus for the S.similar to mitis overall surface properties, autoaggregation and biofilm formation. The capsule deletion resulted in a mutant with approximately two-fold increase in hydrophobicity. Binding to the Stains-all cationic dye was reduced by 40%, suggesting a reduction in the overall negative surface charge of the mutant. The mutant exhibited also increased autoaggregation in coaggregation buffer, and up to six-fold increase in biofilm levels. The results suggested that the capsule locus is associated with production of a capsule-like structure in S.similar to mitis and indicated that the S.similar to mitis capsule-like structure may confer surface attributes similar to those associated with the capsule in S.similar to pneumoniae.