Kamachi Kazunari, Sota Masahiro, Tamai Yuji, Nagata Noriyo, Konda Toshifumi, Inoue Toshiro, Top Eva M, Arakawa Yoshichika
Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1 Gakuen, Musashimurayma, Tokyo 208-0011, Japan.
Department of Biological Sciences, University of Idaho, Moscow, ID 83844-3051, USA.
Microbiology (Reading). 2006 Dec;152(Pt 12):3477-3484. doi: 10.1099/mic.0.29056-0.
The complete 41,268 bp nucleotide sequence of the IncP-1beta plasmid pBP136 from the human pathogen Bordetella pertussis, the primary aetiological agent of whooping cough, was determined and analysed. This plasmid carried a total of 46 ORFs: 44 ORFs corresponding to the genes in the conserved IncP-1beta backbone, and 2 ORFs similar to the XF1596 and XF1597 genes with unknown function of the plant pathogen Xylella fastidiosa. Interestingly, pBP136 had no accessory genes carrying genetic traits such as antibiotic or mercury resistance and/or xenobiotic degradation. Moreover, pBP136 had only two of the kle genes (kleAE) that have been reported to be important for the stability of IncP-1 plasmid in Pseudomonas aeruginosa. Phylogenetic analysis of the Kle proteins revealed that the KleA and KleE of pBP136 were phylogenetically distant from those of the present IncP-1 plasmids. In contrast, IncC1 and KorC, encoded upstream and downstream of the kle genes respectively, and the replication-initiation protein, TrfA, were closely related to those of the IncP-1beta 'R751 group'. These results suggest that (i) pBP136 without any apparent accessory genes diverged early from an ancestor of the present IncP-1beta plasmids, especially those of the R751 group, and (ii) the kle genes might be incorporated independently into the backbone region of the IncP-1 plasmids for their stable maintenance in various host cells.
百日咳博德特氏菌是百日咳的主要病原体，属于人类病原体。对其携带的IncP-1β质粒pBP136的41268 bp完整核苷酸序列进行了测定和分析。该质粒共携带46个开放阅读框（ORF）：44个ORF对应于保守的IncP-1β骨架中的基因，另外2个ORF与植物病原体木质部难养菌功能未知的XF1596和XF1597基因相似。有趣的是，pBP136没有携带抗生素或汞抗性和/或异生物降解等遗传特性的辅助基因。此外，pBP136仅含有两个据报道对IncP-1质粒在铜绿假单胞菌中稳定性很重要的kle基因（kleAE）。对Kle蛋白的系统发育分析表明，pBP136的KleA和KleE在系统发育上与目前的IncP-1质粒的Kle蛋白相距较远。相比之下，分别在kle基因上游和下游编码的IncC1和KorC以及复制起始蛋白TrfA与IncP-1β“R751组”的密切相关。这些结果表明：（i）没有任何明显辅助基因的pBP136较早地从目前IncP-1β质粒的祖先中分化出来，尤其是R751组的祖先；（ii）kle基因可能独立地整合到IncP-1质粒的骨架区域，以便在各种宿主细胞中稳定维持。
