不携带霍乱毒素基因的CTXΦ类前噬菌体基因组克隆与分析  

Clone and Analysis of CTXΦ Prophage Genome Which not Carrying Toxin Genes of Vibrio cholerae

作　　者：阚飙[1] 刘延清[1] 祁国明[1] 章丽娟[1] 高守一[1] 

机构地区：[1]中国预防医学科学院流行病学微生物学研究所,卫生部医学分子细菌学重点实验室,北京102206

出　　处：《微生物学报》2002年第5期573-581,共9页Acta Microbiologica Sinica

基　　金：国家自然科学基金 ( 39870 0 31 );国家重大基础研究项目课题 (G1 9990 5 4 1 0 2 )资助~~

摘　　要：霍乱弧菌的霍乱毒素基因ctxAB由其溶原性噬菌体CTXΦ编码 ,由此携带毒素基因在产毒株与非产毒株间水平转移。从无ctxAB的ElTor型菌株中 ,发现不同时间、地点来源的部分菌株仍带有CTXΦ基因组的其它基因 ,在研究菌株染色体上呈双拷贝串联排列。克隆后测序发现基因组全长 5 70 8bp ,其抑制基因rstR却与古典型菌株来源CTXΦ的相同 ,因此从E1Tor菌株中发现整合有古典型来源的这类噬菌体。其它各基因与CTXΦ序列基本一致 ,但nct CTXΦ的zot基因末端及下游间隔区与CTXΦ的相差很大 ,进一步的序列测定与比较表明nct CTXΦ中无ctxAB应是其固有结构 ,而不是ctxAB丢失所形成的。将这种独特的前噬菌体命名为nct CTXclassΦ。研究菌株染色体上nct CTXΦ基因组上下游也各存在TLC因子和RTX毒力基因簇的同源序列 ,揭示它们与nct CTXΦ基因组有与CTXΦ相同的联系。从序列分析上认为nct CTXΦ与CTXΦ在遗传分化上有不同 ,可能是CTXΦ的前体形式 ,这对CTXΦ的来源。Cholera toxin gene (ctxAB) is encoded by the lysogenic bacteriophage CTXΦ of Vibrio cholerae,and can be transfered horizontally from toxigenic strains to non-toxigenic strains.In our study in the ctxAB - El Tor strains,some of different isolation regions and years were found possessing the isogenous sequences of the other genes of CTXΦ.Two copies of this novel ctxAB - CTXΦ prophage genome linked tandemly in the chromosomal.The whole genome is 5708 bp in length.Its rstR is homologous to the classical-derived CTX classΦ′s,indicates that classical-derived member of CTXΦ family integrates in the chromosome of El Tor strains.The other genes of nct-CTXΦ are highly homologous to those of CTXΦ's,except for zot. The end 15 amino acid residues of Zot are different obviously from the CTXΦ′s.We have disignated this prophage nct-CTX classΦ.TLC element is also in the upstream of nct-CTX classΦ genome,which is considered to play some role in the biology of CTXΦ, and RTX virulence gene cluster in the downstream,suggests their close relationship.In view of its genome characters,it suggests that it has structural basis which does not carry ctxAB, but not the result of the deletion of ctxAB from CTXΦ,nct-CTXΦ should be the precusor of CTXΦ.This may give new proof for the study of the source and divergence of CTXΦ and the emergence of new pathogenic strains of V.cholerae.

关 键 词：霍乱毒素基因 CTXφ类前噬菌体 基因组克隆 溶原性噬菌体 

分 类 号：Q785[生物学—分子生物学]