Adhikari P, Allison G, Whittle B, Verma N K
Division of Biochemistry and Molecular Biology, Faculty of Science, The Australian National University, Canberra, ACT 0200, Australia.
J Bacteriol. 1999 Aug;181(15):4711-8. doi: 10.1128/JB.181.15.4711-4718.1999.
The factors responsible for serotype 1a O-antigen modification in Shigella flexneri were localized to a 5.8-kb chromosomal HindIII fragment of serotype 1a strain Y53. The entire 5.8-kb fragment and regions up- and downstream of it (10.6-kb total) were sequenced. A putative three-gene operon, which showed homology with other serotype conversion genes, was identified and shown to confer serotype 1a O-antigen modification. The serotype conversion genes were flanked on either side by phage DNA. Multiple insertion sequence (IS) elements were located within and upstream of the phage DNA in a composite transposon-like structure. Host DNA homologous to the dsdC and the thrW proA genes was located upstream of the IS elements and downstream of the phage DNA, respectively. The sequence analysis indicates that the organization of the 10.6-kb region of the Y53 chromosome is unique and suggests that the serotype conversion genes were originally brought into the host by a bacteriophage. Several features of this region are also characteristic of pathogenicity islands.
负责福氏志贺菌1a血清型O抗原修饰的因子定位于1a血清型菌株Y53的一个5.8kb染色体HindIII片段。对整个5.8kb片段及其上下游区域（共10.6kb）进行了测序。鉴定出一个假定的三基因操纵子，它与其他血清型转换基因具有同源性，并显示可赋予1a血清型O抗原修饰。血清型转换基因两侧均为噬菌体DNA。多个插入序列（IS）元件以复合转座子样结构位于噬菌体DNA内部和上游。与dsdC和thrW proA基因同源的宿主DNA分别位于IS元件上游和噬菌体DNA下游。序列分析表明，Y53染色体10.6kb区域的组织是独特的，并提示血清型转换基因最初是由噬菌体带入宿主的。该区域的几个特征也是致病岛的特征。
