Type VI secretion is a major virulence determinant in Burkholderia mallei
Type VI secretion is a major virulence determinant in Burkholderia mallei
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DOI：
10.1111/j.1365-2958.2007.05734.x
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发表时间：
2007-06-01
影响因子：
3.6
通讯作者：
DeShazer, David
中科院分区：
文献类型：
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作者：
Schell, Mark A.;Ulrich, Ricky L.;DeShazer, David
鼻疽伯克霍尔德氏菌是一种适应宿主的病原体，属于B类生物威胁因子。虽然B. mallei VirAG双组分调控系统是仓鼠毒力所必需的，其调控的毒力基因尚不清楚。在这里，我们显示与表达谱，过表达的virAG导致转录激活类似的60个基因，包括一些参与胶囊生产，肌动蛋白为基础的细胞内运动，和VI型分泌（T6 S）。编码均聚荚膜的主要糖组分的15个基因上调表达> 2.5倍，但在不存在virAG的情况下仍然产生荚膜。肌动蛋白尾的形成需要virAG以及bimB、bimC和bimE，这三个先前未表征的基因在VirAG过度产生时被激活4至15倍。令人惊讶的是，肌动蛋白聚合被发现是仓鼠的毒力。相比之下，编码T6 S系统的基因上调表达多达30倍，并且该T6 S基因簇中的突变导致在仓鼠中无毒的菌株。SDS-PAGE和质谱分析表明，当virAG过表达时，BMAA 0742由T6 S系统分泌。纯化的His标记的BMAA 0742被马、人和小鼠的鼻疽抗血清识别，表明这种HCP家族蛋白在感染过程中体内产生。
Burkholderia mallei is a host-adapted pathogen and a category B biothreat agent. Although the B. mallei VirAG two-component regulatory system is required for virulence in hamsters, the virulence genes it regulates are unknown. Here we show with expression profiling that overexpression of virAG resulted in transcriptional activation of similar to 60 genes, including some involved in capsule production, actin-based intracellular motility, and type VI secretion (T6S). The 15 genes encoding the major sugar component of the homopolymeric capsule were up-expressed > 2.5-fold, but capsule was still produced in the absence of virAG. Actin tail formation required virAG as well as bimB, bimC and bimE, three previously uncharacterized genes that were activated four- to 15-fold when VirAG was overproduced. Surprisingly, actin polymerization was found to be dispensable for virulence in hamsters. In contrast, genes encoding a T6S system were up-expressed as much as 30-fold and mutations in this T6S gene cluster resulted in strains that were avirulent in hamsters. SDS-PAGE and mass spectrometry demonstrated that BMAA0742 was secreted by the T6S system when virAG was overexpressed. Purified His-tagged BMAA0742 was recognized by glanders antiserum from a horse, a human and mice, indicating that this Hcp-family protein is produced in vivo during infection.