A novel linear plasmid mediates flagellar variation in Salmonella Typhi.
A novel linear plasmid mediates flagellar variation in Salmonella Typhi.
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DOI：
10.1371/journal.ppat.0030059
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发表时间：
2007-05-11
期刊：
影响因子：
6.7
通讯作者：
Dougan, Gordon
中科院分区：
文献类型：
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作者：
Baker, Stephen;Hardy, Jonathan;Sanderson, Kenneth E;Quail, Michael;Goodhead, Ian;Kingsley, Robert A;Parkhill, Julian;Stocker, Bruce;Dougan, Gordon
与大多数肠道沙门氏菌血清型不同，伤寒沙门氏菌（S. Typhi），即人类伤寒的病原体，是单相的。伤寒沙门氏菌通常仅含有第1相鞭毛蛋白基因（fliC），其编码H:d抗原。然而，在印度尼西亚发现的一些伤寒沙门氏菌菌株表达一种额外的鞭毛蛋白抗原，称为H:z66。对H:z66⁺伤寒沙门氏菌的分子分析表明，H:z66鞭毛蛋白结构基因（fljBz66）由一个线性质粒编码，我们将其命名为pBSSB1。pBSSB1的DNA序列测定为略超过27kbp，预计编码33个编码序列。据我们所知，pBSSB1是在肠杆菌科中描述的第一个与噬菌体无关的线性质粒。
鞭毛是细菌细胞表面的鞭状结构，介导游动。鞭毛含有一种称为鞭毛蛋白的蛋白质，它被免疫系统识别为危险信号。伤寒沙门氏菌，即引起伤寒的细菌，通常具有称为H:d的鞭毛，但一些仅来自印度尼西亚的菌株表达独特的鞭毛，称为H:z66。在这项研究中，我们定位并测定了负责表达这些替代鞭毛的基因的序列。值得注意的是，这些基因位于一个线性质粒上，这是一种染色体外元件，我们将其命名为pBSSB1。这一发现的意义在于，线性质粒在链霉菌属和疏螺旋体属等细菌物种中相对常见。然而，这样的线性元件以前从未在大肠杆菌和沙门氏菌等肠道细菌中被描述过。在遗传上易于操作的细菌中鉴定出这种新型线性质粒将有助于未来对线性质粒生物学以及鞭毛和伤寒沙门氏菌致病性的研究。
Unlike the majority of Salmonella enterica serovars, Salmonella Typhi (S. Typhi), the etiological agent of human typhoid, is monophasic. S. Typhi normally harbours only the phase 1 flagellin gene (fliC), which encodes the H:d antigen. However, some S. Typhi strains found in Indonesia express an additional flagellin antigen termed H:z66. Molecular analysis of H:z66+ S. Typhi revealed that the H:z66 flagellin structural gene (fljBz66) is encoded on a linear plasmid that we have named pBSSB1. The DNA sequence of pBSSB1 was determined to be just over 27 kbp, and was predicted to encode 33 coding sequences. To our knowledge, pBSSB1 is the first non-bacteriophage–related linear plasmid to be described in the Enterobacteriaceae. Flagella are whip-like structures found on the surface of bacterial cells that mediate swimming. Flagella contain a protein called flagellin, which is recognised as a danger signal by the immune system. Salmonella Typhi, the bacteria that causes typhoid fever, normally have flagella called H:d, but some strains only from Indonesia express distinct flagella, called H:z66. In this study we have located and sequenced the genes responsible for expressing these alternative flagella. Remarkably, these genes are located on a linear plasmid, an extra-chromosomal element that we have named pBSSB1. The significance of this finding is that linear plasmids are relatively common in bacterial species such as Streptomyces and Borrelia. However, such a linear element has never previously been described in enteric bacteria such as Escherichia coli and Salmonella. The identification of this novel linear plasmid in genetically tractable bacteria will facilitate future studies on the biology of linear plasmids and the pathogenicity of both flagella and Salmonella Typhi.