Enteric Bacterial Pathogens Laboratory, Institute for Animal Health, Compton, Berkshire RG20 7NN, UK.
Microbiology (Reading). 2010 Oct;156(Pt 10):3108-3122. doi: 10.1099/mic.0.041830-0. Epub 2010 Jul 23.
Salmonella enterica serovar Dublin (S. Dublin) is associated with enteritis, typhoid and abortion in cattle. Infections are acquired by the oral route, and the bacteria transit through varied anatomical and cellular niches to elicit systemic disease. S. Dublin must therefore sense and respond to diverse extrinsic stimuli to control gene expression in a spatial and temporal manner. Two-component systems (TCSs) play key roles in such processes, and typically contain a membrane-associated sensor kinase (SK) that modifies a cognate response regulator. Analysis of the genome sequence of S. Dublin identified 31 conserved SK genes. Each SK gene was separately disrupted by lambda Red recombinase-mediated insertion of transposons harbouring unique sequence tags. Calves were challenged with a pool of the mutants together with control strains of defined virulence by the oral and intravenous routes. Quantification of tagged mutants in output pools derived from various tissues and cannulated lymphatic vessels allowed the assignment of spatial roles for each SK following oral inoculation or when the intestinal barrier was bypassed by intravenous delivery. Mutant phenotypes were also assigned in cultured intestinal epithelial cells. Mutants with insertions in barA, envZ, phoQ, ssrA or qseC were significantly negatively selected at all enteric and systemic sites sampled after oral dosing. Mutants lacking baeS, dpiB or citA were negatively selected at some but not all sites. After intravenous inoculation, only barA and phoQ mutants were significantly under-represented at systemic sites. The novel role of baeS in intestinal colonization was confirmed by oral co-infection studies, with a mutant exhibiting modest but significant attenuation at a number of enteric sites. This is the first systematic analysis of the role of all Salmonella TCSs in a highly relevant model of enteric fever. Spatial roles were assigned to eight S. Dublin SKs, but most were not essential for intestinal or systemic infection of the target host.
都柏林沙门氏菌（S. Dublin）与牛的肠炎、伤寒和流产有关。感染是通过口服途径获得的，细菌通过各种解剖和细胞小生境传播，引起全身疾病。因此，S. Dublin 必须感知和响应各种外在刺激，以时空方式控制基因表达。双组分系统（TCS）在这些过程中起着关键作用，通常包含一个膜相关的传感器激酶（SK），它修饰同源反应调节剂。对 S. Dublin 基因组序列的分析确定了 31 个保守的 SK 基因。每个 SK 基因都分别通过 lambda Red 重组酶介导的转座子插入来破坏，这些转座子携带独特的序列标签。通过口服和静脉途径，用突变体池和具有明确毒力的对照菌株对小牛进行挑战。从各种组织和插管淋巴管衍生的输出池定量标记突变体，允许在口服接种后或通过静脉递送绕过肠道屏障时为每个 SK 分配空间作用。在培养的肠上皮细胞中也分配了突变表型。在 barA、envZ、phoQ、ssrA 或 qseC 插入突变体在口服给药后所有肠内和系统采样部位均被显著负选择。缺乏 baeS、dpiB 或 citA 的突变体在某些但不是所有部位被负选择。静脉接种后，只有 barA 和 phoQ 突变体在系统部位的代表性明显降低。通过口服共感染研究证实了 baeS 在肠道定植中的新作用，突变体在许多肠道部位表现出适度但显著的衰减。这是首次对所有沙门氏菌 TCS 在高度相关的肠热病模型中的作用进行系统分析。为 8 个 S. Dublin SK 分配了空间作用，但大多数在肠道或系统感染靶宿主方面不是必需的。
