Deletion of TolC orthologs in Francisella tularensis identifies roles in multidrug resistance and virulence
Deletion of TolC orthologs in Francisella tularensis identifies roles in multidrug resistance and virulence
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DOI：
10.1073/pnas.0602582103
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发表时间：
2006-08-22
影响因子：
11.1
通讯作者：
Thanassi, David G.
中科院分区：
文献类型：
--
作者：
Gil, Horacio;Platz, Gabrielle J.;Thanassi, David G.
革兰氏阴性杆菌是图拉热症的病原体。由于它被归类为生物恐怖主义的A类病原体，人们对这种人畜共患病病原体的兴趣有所增加，但人们对其毒力背后的分子机制知之甚少，特别是存在哪些分泌系统和毒力因子。在这项研究中，我们鉴定了图拉氏杆菌基因组中的两个基因toIC和一个我们称为fltc的基因，其产物与大肠杆菌ToIC蛋白有很高的同源性。ToIC作为I型分泌物和多药外排系统的外膜通道成分。我们用等位基因置换的方法构建了图拉氏F菌活疫苗株中这些基因的缺失突变。ToIC或WC的缺失导致对各种抗生素、洗涤剂和染料的敏感性增加，这表明这两个基因都参与了图拉氏革兰氏杆菌的多药耐药机制。反式缺失突变的互补恢复耐药。在小鼠骨髓来源的巨噬细胞中复制活疫苗株既不需要TOIC，也不需要FltC。然而，在图拉热症的小鼠模型中，toIC的缺失，而不是fltc的缺失，导致了毒力的显著减弱，这可以通过在反式中添加toIC来补充。因此，toIC除了在多药耐药中发挥作用外，还是图拉氏福氏杆菌的一个关键毒力因子，这表明存在一种功能性的I型分泌系统。
The Gram-negative bacterium Francisella tularensis is the causative agent of tularemia. Interest in this zoonotic pathogen has increased due to its classification as a category A agent of bioterrorism, but little is known about the molecular mechanisms underlying its virulence, and especially what secretion systems and virulence factors are present. In this study, we characterized two genes in the F. tularensis genome, toIC and a gene we term fltC, whose products have high homology with the Escherichia coli ToIC protein. ToIC functions as the outer membrane channel component for both type I secretion and multidrug efflux systems. We constructed deletion mutations of these genes in the F. tularensis live vaccine strain by allelic replacement. Deletion of either toIC or WC caused increased sensitivity to various antibiotics, detergents, and dyes, indicating both genes are involved in the multidrug resistance machinery of F. tularensis. Complementation of the deletion mutations in trans restored drug resistance. Neither toIC nor fltC was required for replication of the live vaccine strain in murine bone marrow-derived macrophages. However, deletion of toIC, but not fltC, caused a significant attenuation of virulence in a mouse model of tularemia that could be complemented by addition of toIC in trans. Thus, toIC is a critical virulence factor of F. tularensis in addition to its role in multidrug resistance, which suggests the presence of a functional type I secretion system.