Franken C, Haase G, Brandt C, Weber-Heynemann J, Martin S, Lämmler C, Podbielski A, Lütticken R, Spellerberg B
Institute of Medical Microbiology and National Reference Center for Streptococci, University Hospital Aachen, Pauwelsstr. 30, 52057 Aachen, Germany.
Mol Microbiol. 2001 Aug;41(4):925-35. doi: 10.1046/j.1365-2958.2001.02563.x.
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 lmb, 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 lmb or their homologues. To investigate if the putative transposon can be mobilized, an erythromycin resistance marker was incorporated into the lmb gene of S. agalactiae. Screening for mutant strains with a regained susceptibility for erythromycin identified strains with a deletion of scpB, lmb, and one copy of ISSag2. We hypothesize that a horizontal gene transfer caused the exchange of scpB and lmb 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.
β-溶血性链球菌是重要的人类和动物病原体：然而，它们与感染人类宿主能力相关的遗传特征仍不清楚。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基因，对其相邻的基因组区域进行了测序。Lmb位于一个推定的16 kb复合转座子上，两侧是新型插入序列元件（ISSag2）的两个拷贝。它含有scpB和lmb基因，与化脓性链球菌的相应基因有98%的同一性。对131株链球菌菌株中这些基因和ISSag2的分布分析表明，所有人类分离株，但只有20%（61株中的12株）动物分离株含有scpB和lmb或其同源物。为了研究推定的转座子是否可以被激活，将红霉素抗性标记引入无乳链球菌的lmb基因中。筛选对红霉素重新敏感的突变菌株，鉴定出scpB、lmb和一个ISSag2拷贝缺失的菌株。我们推测水平基因转移导致了scpB和lmb的交换，并且化脓性链球菌、无乳链球菌以及C组和G组链球菌菌株定殖或感染人类宿主的能力取决于它们的存在。
