Karaolis D K, Johnson J A, Bailey C C, Boedeker E C, Kaper J B, Reeves P R
Center for Vaccine Development, University of Maryland School of Medicine, Baltimore, MD 21201, USA.
Proc Natl Acad Sci U S A. 1998 Mar 17;95(6):3134-9. doi: 10.1073/pnas.95.6.3134.
The bacterial species Vibrio cholerae includes harmless aquatic strains as well as strains capable of causing epidemics and global pandemics of cholera. While investigating the relationship between pathogenic and nonpathogenic strains, we identified a chromosomal pathogenicity island (PAI) that is present in epidemic and pandemic strains but absent from nonpathogenic strains. Initially, two ToxR-regulated genes (aldA and tagA) were studied and were found to be associated with epidemic and pandemic strains but absent in nontoxigenic strains. The region containing aldA and tagA comprises 13 kb of previously unidentified DNA and is part of a PAI that contains a regulator of virulence genes (ToxT) and a gene cluster encoding an essential colonization factor and the cholera toxin phage receptor (toxin-coregulated pilus; TCP). The PAI is 39.5 kb in size, has low %G+C (35%), contains putative integrase and transposase genes, is flanked by att sites, and inserts near a 10Sa RNA gene (ssrA), suggesting it may be of bacteriophage origin. We found this PAI in two clinical non-O1/non-O139 cholera toxin-positive strains, suggesting that it can be transferred within V. cholerae. The sequence within this PAI includes an ORF with homology to a gene associated with the type IV pilus gene cluster of enteropathogenic Escherichia coli, a transposase from Vibrio anguillarum, and several ORFs with no known homology. As the PAI contains the CTXPhi receptor, it may represent the initial genetic factor required for the emergence of epidemic and pandemic cholera. We propose to call this island VPI (V. cholerae pathogenicity island).
霍乱弧菌这一细菌物种既包括无害的水生菌株，也包括能够引发霍乱流行和全球大流行的菌株。在研究致病性菌株与非致病性菌株之间的关系时，我们鉴定出了一个染色体致病岛（PAI），该致病岛存在于流行菌株和大流行菌株中，但在非致病性菌株中不存在。最初，对两个受ToxR调控的基因（aldA和tagA）进行了研究，发现它们与流行菌株和大流行菌株相关，但在非产毒菌株中不存在。包含aldA和tagA的区域由13 kb先前未鉴定的DNA组成，是一个PAI的一部分，该PAI包含一个毒力基因调节因子（ToxT）以及一个编码必需定植因子和霍乱毒素噬菌体受体（毒素协同调节菌毛；TCP）的基因簇。该PAI大小为39.5 kb，G+C含量低（35%），包含推测的整合酶和转座酶基因，两侧为附着位点，并插入到一个10Sa RNA基因（ssrA）附近，这表明它可能起源于噬菌体。我们在两株临床非O1/非O139霍乱毒素阳性菌株中发现了这个PAI，这表明它可以在霍乱弧菌内转移。该PAI内的序列包括一个与肠致病性大肠杆菌IV型菌毛基因簇相关基因具有同源性的开放阅读框、一个来自鳗弧菌的转座酶，以及几个无已知同源性的开放阅读框。由于该PAI包含CTXPhi受体，它可能代表了流行和大流行霍乱出现所需的初始遗传因素。我们提议将这个岛称为VPI（霍乱弧菌致病岛）。
