Conjugative Plasmids of Neisseria gonorrhoeae
Conjugative Plasmids of Neisseria gonorrhoeae
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DOI：
10.1371/journal.pone.0009962
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发表时间：
2010-04-01
期刊：
影响因子：
3.7
通讯作者：
van der Does, Chris
中科院分区：
文献类型：
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作者：
Pachulec, Emilia;van der Does, Chris
许多人类病原体淋病奈瑟菌的临床分离株都含有接合质粒。这些质粒的宿主范围仅限于奈瑟氏菌，但其中几个质粒中插入的四环素决定簇是四环素耐药性迅速传播的重要原因。以前已经确定了具有不同骨架(荷兰和美国类型的骨架)以及具有和不具有不同的TETM决定簇(荷兰和美国类型的TETM决定簇)的质粒。在测试的菌株中，所有带有美国或荷兰型TETM决定簇的质粒都含有荷兰型质粒骨架。这表明，不应使用TETM决定簇来区分结合质粒骨架。测定了不含TETM决定簇(PEP5233)和含有荷兰(PEP5289)或美国(PEP5050)型TETM决定簇的荷兰型质粒骨架的接合质粒的核苷酸序列。对骨架序列的分析表明，它们属于一个新的IncP1亚家族，它与IncP1α、β、伽马、Delta和epsilon亚家族有所不同。TETM决定簇被插入到在所有这些质粒中发现的遗传负荷区。插入伴随着一个功能未知的基因的插入，以及毒素/抗毒素基因簇的重排。基因负荷区包含两种毒素/抗毒素，一种是以前仅在革兰氏阳性生物中发现的Zeta/Epsilon毒素/抗毒素家族的毒素/抗毒素，另一种是VapD/VapX毒素/抗毒素家族的毒力相关蛋白D。显著地，pJD1的VapX在受体菌株中的存在显著地提高了接合效率，这表明它对接合的质粒具有抗毒素的作用。不同质粒上毒素和抗毒素的存在可能解释了为什么该IncP1质粒的寄主范围仅限于奈瑟氏菌。分离的质粒在淋球菌菌株之间有效地结合，但不能促进遗传标记的转移。
Many clinical isolates of the human pathogen Neisseria gonorrhoeae contain conjugative plasmids. The host range of these plasmids is limited to Neisseria species, but presence of a tetracycline (tetM) determinant inserted in several of these plasmids is an important cause of the rapid spread of tetracycline resistance. Previously plasmids with different backbones (Dutch and American type backbones) and with and without different tetM determinants (Dutch and American type tetM determinants) have been identified. Within the isolates tested, all plasmids with American or Dutch type tetM determinants contained a Dutch type plasmid backbone. This demonstrated that tetM determinants should not be used to differentiate between conjugal plasmid backbones. The nucleotide sequences of conjugative plasmids with Dutch type plasmid backbones either not containing the tetM determinant (pEP5233) or containing Dutch (pEP5289) or American (pEP5050) type tetM determinants were determined. Analysis of the backbone sequences showed that they belong to a novel IncP1 subfamily divergent from the IncP1 alpha, beta, gamma, delta and epsilon subfamilies. The tetM determinants were inserted in a genetic load region found in all these plasmids. Insertion was accompanied by the insertion of a gene with an unknown function, and rearrangement of a toxin/antitoxin gene cluster. The genetic load region contains two toxin/antitoxins of the Zeta/Epsilon toxin/antitoxin family previously only found in Gram positive organisms and the virulence associated protein D of the VapD/VapX toxin/antitoxin family. Remarkably, presence of VapX of pJD1, a small cryptic neisserial plasmid, in the acceptor strain strongly increased the conjugation efficiency, suggesting that it functions as an antitoxin for the conjugative plasmid. The presence of the toxin and antitoxin on different plasmids might explain why the host range of this IncP1 plasmid is limited to Neisseria species. The isolated plasmids conjugated efficiently between N. gonorrhoeae strains, but did not enhance transfer of a genetic marker.