Nakanishi S, Tazumi A, Moore J E, Millar B C, Matsuda M
Laboratory of Molecular Biology, Graduate School of Environmental Health Sciences, Azabu University, Sagamihara, Japan.
Br J Biomed Sci. 2010;67(4):208-15. doi: 10.1080/09674845.2010.11730321.
Molecular and comparative analyses of the full-length cytolethal distending toxin (cdt) gene operon and its adjacent genetic loci (2.7-9.4 kilo base pairs in length) are carried out with 12 urease-positive thermophilic Campylobacter (UPTC) isolates using several polymerase chain reaction (PCR) primer pairs. Three putative open reading frames (ORFs) for cdtA, cdtB and cdtC, two putative promoters and a hypothetically intrinsic rho-independent transcription terminator were identified in all the operons of the 12 UPTC isolates examined. Although the number of amino acid residues slightly varied for the putative cdtA and cdtC ORFs, those for the cdtB were similar among all the UPTC isolates, as well as the six urease-negative (UN) C. lari examined previously. Regarding the cdt genes in UPTC CF89-12, each ORF commenced with an ATG start codon and terminated with a TAG stop codon for cdtA and cdtB and a TAA for cdtC. Start and stop codons of the three ORFs for the other 11 UPTC isolates were identical to those from the UPTC CF89-12 isolate except for the TTG start codon for cdtC in the two isolates (NCTC12892 and 12893) and the TGA stop codon for cdtA in five isolates (A1, A2, A3, 89049 and 92251). Two putative promoter structures, consisting of sequences at the -35-like (TTAATA) and -10-like (TATTAA) regions, as well as the start codon (ATG), were identified for the transcriptional promoter, immediately upstream of the cdtA gene in all the 12 isolates, Although the genetic heterogeneity of the cdtB gene locus occurred in all 28 C. lari isolates (n = 16 UN C. lari; n = 12 UPTC) examined, all nine amino acid-specific DNase residues were completely conserved in all their cdtB genes. Variable gene insertions with heterogeneous order and combinations occurred between cdtC and lpxB genes in the all UPTC organisms examined.
使用几种聚合酶链反应（PCR）引物对，对12株脲酶阳性嗜热弯曲菌（UPTC）分离株的全长细胞致死膨胀毒素（cdt）基因操纵子及其相邻基因位点（长度为2.7 - 9.4千碱基对）进行了分子和比较分析。在所检测的12株UPTC分离株的所有操纵子中，鉴定出了cdtA、cdtB和cdtC的三个推定开放阅读框（ORF）、两个推定启动子和一个假定的固有ρ因子非依赖性转录终止子。尽管推定的cdtA和cdtC ORF的氨基酸残基数略有不同，但所有UPTC分离株以及先前检测的6株脲酶阴性（UN）海鸥弯曲菌中cdtB的氨基酸残基数相似。关于UPTC CF89 - 12中的cdt基因，每个ORF以ATG起始密码子开始，cdtA和cdtB以TAG终止密码子结束，cdtC以TAA结束。除了两个分离株（NCTC12892和12893）中cdtC的TTG起始密码子以及五个分离株（A1、A2、A3、89049和92251）中cdtA的TGA终止密码子外，其他11株UPTC分离株的三个ORF的起始和终止密码子与UPTC CF89 - 12分离株的相同。在所有12株分离株中，在cdtA基因上游紧邻处鉴定出了由 - 35样（TTAATA）和 - 10样（TATTAA）区域的序列以及起始密码子（ATG）组成的两个推定启动子结构。尽管在所检测的所有28株海鸥弯曲菌分离株（n = 16株UN海鸥弯曲菌；n = 12株UPTC）中cdtB基因位点存在遗传异质性，但其所有cdtB基因中的9个氨基酸特异性DNase残基完全保守。在所检测的所有UPTC菌株中，cdtC和lpxB基因之间发生了具有异质顺序和组合的可变基因插入。
