Identification of MrtAB, an ABC Transporter Specifically Required for Yersinia pseudotuberculosis to Colonize the Mesenteric Lymph Nodes
Identification of MrtAB, an ABC Transporter Specifically Required for Yersinia pseudotuberculosis to Colonize the Mesenteric Lymph Nodes
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DOI：
10.1371/journal.ppat.1002828
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发表时间：
2012-08-01
期刊：
影响因子：
6.7
通讯作者：
Mecsas, Joan
中科院分区：
文献类型：
--
作者：
Crimmins, Gregory T.;Mohammadi, Sina;Mecsas, Joan
一个高度保守的毒力质粒编码III型分泌系统，由三种对哺乳动物最具致病性的耶尔森氏菌共享。虽然该质粒上编码的因子增强了耶尔森氏菌在哺乳动物宿主中茁壮成长的能力，但这种毒力质粒的丧失并不会消除宿主器官的生长或存活。最值得注意的是，在肠系膜淋巴结内，活的缺乏质粒的假结核耶尔森菌(Yptb)的产量与野生型Yptb没有什么区别。为了确定在小鼠系统感染期间允许非质粒型生存的染色体毒力因子，我们在缺乏质粒的Yptb中产生了转座子插入，并筛选了一个包含20,000多个序列识别插入的文库。在以前未确定的基因座中，编码ABC家族转运蛋白的操纵子mrtAB的插入在缺乏质粒的背景下具有最深刻的表型。然而，缺少mrtAB对具有完整毒力质粒的野生型菌株在肝脏和脾中的生长没有影响，但导致肠系膜淋巴结定植的严重缺陷。虽然这一结果与Wt Yptb在肠系膜淋巴结中缺乏III型分泌系统的表达是一致的，但YopE的一名记者表示该系统的表达是强劲的。我们证明了mrtB的ATPase活性是小鼠生长所必需的，这表明毒力需要转运活性。事实上，由于ATPase活性增强了对溴乙锭的抗性，同时增加了对绿青素的敏感性，与内膜的出口一致，因此MRtAB似乎起到了外排泵的作用。
A highly conserved virulence plasmid encoding a type III secretion system is shared by the three Yersinia species most pathogenic for mammals. Although factors encoded on this plasmid enhance the ability of Yersinia to thrive in their mammalian hosts, the loss of this virulence plasmid does not eliminate growth or survival in host organs. Most notably, yields of viable plasmid-deficient Yersinia pseudotuberculosis (Yptb) are indistinguishable from wild-type Yptb within mesenteric lymph nodes. To identify chromosomal virulence factors that allow for plasmid-independent survival during systemic infection of mice, we generated transposon insertions in plasmid-deficient Yptb, and screened a library having over 20,000 sequence-identified insertions. Among the previously uncharacterized loci, insertions in mrtAB, an operon encoding an ABC family transporter, had the most profound phenotype in a plasmid-deficient background. The absence of MrtAB, however, had no effect on growth in the liver and spleen of a wild type strain having an intact virulence plasmid, but caused a severe defect in colonization of the mesenteric lymph nodes. Although this result is consistent with lack of expression of the type III secretion system by Wt Yptb in the mesenteric lymph nodes, a reporter for YopE indicated that expression of the system was robust. We demonstrate that the ATPase activity of MrtB is required for growth in mice, indicating that transport activity is required for virulence. Indeed, MrtAB appears to function as an efflux pump, as the ATPase activity enhances resistance to ethidium bromide while increasing sensitivity to pyocyanin, consistent with export across the inner membrane.