TRANSPOSON MUTAGENESIS OF TYPE-III GROUP-B STREPTOCOCCUS - CORRELATION OF CAPSULE EXPRESSION WITH VIRULENCE
TRANSPOSON MUTAGENESIS OF TYPE-III GROUP-B STREPTOCOCCUS - CORRELATION OF CAPSULE EXPRESSION WITH VIRULENCE
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DOI：
10.1073/pnas.84.20.7208
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发表时间：
1987-10-01
影响因子：
11.1
通讯作者：
KASPER, DL
中科院分区：
文献类型：
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作者：
RUBENS, CE;WESSELS, MR;KASPER, DL
III型B族链球菌（GBS）的荚膜多糖被认为是该生物体毒力的主要因素。转座子诱变用于获得GBS血清型III临床分离株（COH 31 r/s）的等基因菌株，该菌株在负责胶囊产生的基因中具有位点特异性突变。在与粪链球菌菌株CG 110在膜滤器上孵育期间，将自接合转座子Tn 916转移到菌株COH 31 r/s。11个transconjugant克隆不结合III型GBS抗血清的免疫印迹。免疫荧光，竞争性ELISA，和电子显微镜证实，在一个transconjugants，COH 31-15的情况下，检测GBS III型荚膜多糖。用Tn 916探针的Southern杂交分析证实了每个突变体内存在转座子序列。从突变体COH 31-15亚克隆Tn 916序列侧翼的3.0-内切酶EcoRI片段。该片段与来自其他GBS血清型的DNA共享同源性，表明不同荚膜类型的生物体共享的荚膜的共同序列。在新生大鼠模型中，荚膜表达的丧失导致毒力丧失。我们的结论是，一个共同的所有荚膜类型的GBS的基因是必需的III型荚膜的表面表达，该基因的失活Tn 916的结果在丧失毒力。
The capsular polysaccharide of type III group B Streptococcus (GBS) is thought to be a major factor in virulence of this organism. Transposon mutagenesis was used to obtain isogenic strains of a GBS serotype III clinical isolate (COH 31r/s) with site-specific mutations in the gene(s) responsible for capsule production. The self-conjugative transposon Tn916 was transferred to strain COH 31r/s during incubation with Streptococcus faecalis strain CG110 on membrane filters. Eleven transconjugant clones did not bind type III GBS antiserum by immunoblot. Immunoflourescence, competitive ELISA, and electron microscopy confirmed the absence of detectable GBS type III capsular polysaccharide in one of the transconjugants, COH 31-15. Southern hybridization analysis with a Tn916 probe confirmed the presence of the transposon sequence within each mutant. A 3.0-kilobase EcoRI fragment that flanked the Tn916 sequence was subcloned from mutant COH 31-15. This fragment shared homology with DNA from the other GBS serotypes, suggesting a common sequence for capsulation shared by organisms of different capsular types. Loss of capsule expression resulted in loss of virulence in a neonatal rat model. We conclude that a gene common to all capsular types of GBS is required for surface expression of the type III capsule and that inactivation of this gene by Tn916 results in the loss of virulence.