Horizontal gene transfer and host specificity of beta-haemolytic streptococci:: the role of a putative composite transposon containing scpB and lmb
Horizontal gene transfer and host specificity of beta-haemolytic streptococci:: the role of a putative composite transposon containing scpB and lmb
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DOI：
10.1046/j.1365-2958.2001.02563.x
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发表时间：
2001-08-01
影响因子：
3.6
通讯作者：
Spellerberg, B
中科院分区：
文献类型：
--
作者：
Franken, C;Haase, G;Spellerberg, B
β-溶血性链球菌是重要的人类和动物病原体：然而，其与感染人类宿主的能力相关的遗传特征仍然不清楚。表面蛋白Lmb介导无乳链球菌与人层粘连蛋白的粘附。为了进一步分析相应的基因，对相邻的基因组区域进行测序。Lmb位于一个16 kb的假定复合转座子上，两侧是两个拷贝的新插入序列元件（ISSag 2）。它含有scpB和Imb基因，与化脓性链球菌的相应基因具有98%的同一性。这些基因和ISSag 2的分布在131链球菌菌株的分析表明，所有的人分离株，但只有20%（12 61）的动物分离株，含有scpB和Imb或其同源物。为了研究假定的转座子是否可以被调动，将红霉素抗性标记掺入到S.无乳。筛选对红霉素恢复敏感性的突变菌株，鉴定出scpB、Imb和一个ISSag 2拷贝缺失的菌株。我们推测，水平基因转移引起scpB和Imb的交换，S. pyogenes、S.无乳链球菌和C组和G组链球菌菌株定植或感染人类宿主取决于它们的存在。
Beta-haemolytic streptococci are important human and animal pathogens: their genetic traits that are associated with the ability to infect human hosts remain, however, unclear. The surface protein, Lmb, mediates the adherence of Streptococcus agalactiae to human laminin. For further analysis of the corresponding gene, the adjacent genomic regions were sequenced. Lmb is localized on a putative composite transposon of 16 kb and is flanked by two copies of a novel insertion sequence element (ISSag2). It harbours the genes scpB and Imb, which are 98% identical with the respective genes of Streptococcus pyogenes. Analysis of the distribution of these genes and ISSag2 among 131 streptococcal strains revealed that all of the human isolates, but only 20% (12 of 61) of the animal isolates, contained scpB and Imb or their homologues. To investigate if the putative transposon can be mobilized, an erythromycin resistance marker was incorporated into the Imb gene of S. agalactiae. Screening for mutant strains with a regained susceptibility for erythromycin identified strains with a deletion of scpB, Imb, and one copy of ISSag2. We hypothesize that a horizontal gene transfer caused the exchange of scpB and Imb and that the ability of S. pyogenes, S. agalactiae and group C and G streptococcal strains to colonize or infect human hosts is dependent on their presence.