Identification and Characterization of a Novel Type III Secretion System in trh-Positive Vibrio parahaemolyticus Strain TH3996 Reveal Genetic Lineage and Diversity of Pathogenic Machinery beyond the Species Level
Identification and Characterization of a Novel Type III Secretion System in trh-Positive Vibrio parahaemolyticus Strain TH3996 Reveal Genetic Lineage and Diversity of Pathogenic Machinery beyond the Species Level
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DOI：
10.1128/iai.01184-08
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发表时间：
2009-02-01
影响因子：
3.1
通讯作者：
Honda, Takeshi
中科院分区：
文献类型：
--
作者：
Okada, Natsumi;Iida, Tetsuya;Honda, Takeshi
副溶血性弧菌是一种引起食源性胃肠炎的细菌病原体。对具有神奈川现象（Kanagawa phenomenon， KP）的副溶血性弧菌RIMD2210633进行全基因组测序，发现其III型分泌系统（T3SS）的两组基因分别位于1号和2号染色体T3SS1和T3SS2上。虽然RIMD2210633菌株的T3SS2被认为与人类致病性有关，即肠毒性，但在同样对人类致病的trh阳性（kp阴性）副溶血性弧菌菌株中未发现T3SS2基因。在本研究中，对一株trh阳性副溶血性弧菌TH3996株的trh基因周围约100 kb的DNA区域进行了测序，并确定了其遗传组织。这表明在该区域存在一种新的T3SS基因。动物实验使用一个基因的缺失突变株（vscC2）用于新的T3SS装置，表明T3SS对TH3996菌株的肠毒性是必不可少的。PCR分析结果显示，所有trh阳性的副溶血性弧菌株均含有新的T3SS相关基因。系统发育分析表明，虽然新的T3SS与kp阳性副溶血性弧菌的T3SS2密切相关，但它属于一个明显不同的谱系。此外，在致病性霍乱弧菌非o1 /非o139株中也发现了两种类型的T3SS2谱系。我们的研究结果表明，这两种不同类型的弧菌不仅分布在一个物种内，而且还分布在物种水平之外，并为弧菌物种的致病性和进化提供了新的见解。
Vibrio parahaemolyticus is a bacterial pathogen causative of food-borne gastroenteritis. Whole-genome sequencing of V. parahaemolyticus strain RIMD2210633, which exhibits Kanagawa phenomenon (KP), revealed the presence of two sets of the genes for the type III secretion system (T3SS) on chromosomes 1 and 2, T3SS1 and T3SS2, respectively. Although T3SS2 of the RIMD2210633 strain is thought to be involved in human pathogenicity, i. e., enterotoxicity, the genes for T3SS2 have not been found in trh-positive (KP-negative) V. parahaemolyticus strains, which are also pathogenic for humans. In the study described here, the DNA region of approximately 100 kb that surrounds the trh gene of a trh-positive V. parahaemolyticus strain, TH3996, was sequenced and its genetic organization determined. This revealed the presence of the genes for a novel T3SS in this region. Animal experiments using the deletion mutant strains of a gene (vscC2) for the novel T3SS apparatus indicated that the T3SS is essential for the enterotoxicity of the TH3996 strain. PCR analysis showed that all the trh-positive V. parahaemolyticus strains tested possess the novel T3SS- related genes. Phylogenetic analysis demonstrated that although the novel T3SS is closely related to T3SS2 of KP-positive V. parahaemolyticus, it belongs to a distinctly different lineage. Furthermore, the two types of T3SS2 lineage are also found among pathogenic Vibrio cholerae non-O1/non-O139 strains. Our findings demonstrate that these two distinct types are distributed not only within a species but also beyond the species level and provide a new insight into the pathogenicity and evolution of Vibrio species.