Bik E M, Bunschoten A E, Willems R J, Chang A C, Mooi F R
Research Laboratory for Infectious Diseases, National Institute of Public Health and the Environment, Bilthoven, The Netherlands.
Mol Microbiol. 1996 May;20(4):799-811. doi: 10.1111/j.1365-2958.1996.tb02518.x.
In 1992 a new Vibrio cholerae strain, designated V. cholerae O139 Bengal, emerged which has been responsible for large outbreaks of cholera in India and Bangladesh. Previously, we have shown that this strain arose from a V. cholerae O1 strain by the acquisition of novel DNA. Sequence analysis revealed that the novel DNA is flanked by two genes, rfaD and rfbQRS, which are also found in O1 strains. The mosaic structure of rfaDVCO139 indicated that it was one of the regions involved in recombination between donor and acceptor DNA. However, sequence divergence between the O1 and O139 rfbQRS genes indicated that the second recombination site between donor and O1-acceptor DNA is probably located downstream of rfbDVCO139. The DNA region between rfaDVCO139 and rfbQRSVCO139, designated otn, contained seven open reading frames (ORFs). Two ORFs, otnA and otnB, showed homology with genes involved in cell-wall polysaccharide synthesis. Mutations in otnA and otnB indicated that they are required for capsule synthesis but not lipopolysaccharide synthesis. The otn DNA is also found in V. cholerae O69 and O141 strains, and the organization of this DNA was essentially identical to that in the O139 strain. However, sequence divergence of the otnAB genes indicated that the O139 otn DNA region was not derived from the O69 or O141 strains. No antigenic relationship was found between the different V. cholerae serotypes carrying otn DNA, so the genes determining the antigenic specificity of the O antigen or capsule must be located outside the otn DNA. The O139 otn DNA contained a JUMPstart sequence, which is associated with polysaccharide-synthetic genes in several bacterial species. Furthermore, a repeat motif was observed in extragenic regions. A number of observations suggest that these sequences may facilitate gene flow between V. cholerae strains and the assembly of clusters of functionally related genes.
1992年，一种新的霍乱弧菌菌株出现，被命名为霍乱弧菌O139孟加拉型，它在印度和孟加拉国引发了大规模霍乱疫情。此前，我们已表明该菌株是通过获取新的DNA从霍乱弧菌O1菌株演变而来。序列分析显示，新的DNA两侧是两个基因，rfaD和rfbQRS，它们在O1菌株中也能找到。rfaDVCO139的镶嵌结构表明它是供体和受体DNA之间重组所涉及的区域之一。然而，O1和O139 rfbQRS基因之间的序列差异表明，供体和O1受体DNA之间的第二个重组位点可能位于rfbDVCO139的下游。rfaDVCO139和rfbQRSVCO139之间的DNA区域，命名为otn，包含七个开放阅读框（ORF）。两个ORF，otnA和otnB，与参与细胞壁多糖合成的基因显示出同源性。otnA和otnB中的突变表明它们是荚膜合成所必需的，但不是脂多糖合成所必需的。otn DNA也存在于霍乱弧菌O69和O141菌株中，并且该DNA的组织与O139菌株中的基本相同。然而，otnAB基因的序列差异表明O139 otn DNA区域并非源自O69或O141菌株。在携带otn DNA的不同霍乱弧菌血清型之间未发现抗原关系，因此决定O抗原或荚膜抗原特异性的基因必定位于otn DNA之外。O139 otn DNA包含一个JUMPstart序列，它与几种细菌物种中的多糖合成基因相关。此外，在外源区域观察到一个重复基序。一些观察结果表明，这些序列可能促进霍乱弧菌菌株之间的基因流动以及功能相关基因簇的组装。
