Young G M, Miller V L
Department of Microbiology and Molecular Genetics, University of California, Los Angeles 90095, USA.
Mol Microbiol. 1997 Jul;25(2):319-28. doi: 10.1046/j.1365-2958.1997.4661829.x.
Pathogenic species of the genus Yersinia have a marked tropism for lymphoid tissue during the early stages of infection. Bacterial survival at this site determines whether the disease is localized or progresses systemically, leading to a high rate of mortality. Several plasmid-encoded virulence genes are known to be required for survival and pathogenesis, but the contribution of chromosomal genes has been largely unexplored. This study represents the first intensive effort to characterize and determine the function of Yersinia chromosomal genes expressed in lymphoid tissue after intragastric infection. Strains harbouring cat fusions expressed in the host were isolated from Peyer's patch tissue of mice intragastrically infected and treated with chloramphenicol (Cm); genes identified in this manner were designated hre for host responsive element. The hre::cat strains that were Cm resistant in vivo (in mouse tissue) and Cm sensitive in vitro (on laboratory media at 26 degrees C) were identified and shown to consist of 61 different allelic groups. The hre::cat fusions from 48 of the allelic groups were cloned and characterized by DNA sequence analysis. The results identified genes necessary for iron acquisition, protection from environmental stresses, biosynthesis of cell envelope components and other diverse metabolic activities. However, the DNA sequence of many clones had no homology to other known genes. Insertion mutations were constructed for four hre genes and the resulting Y. enterocolitica mutants were tested in the mouse model for effects on pathogenesis. All of the mutant strains were affected for virulence when assayed for survival in host tissues and LD50 analysis.
耶尔森氏菌属的致病菌种在感染早期对淋巴组织具有明显的嗜性。细菌在该部位的存活决定了疾病是局限化还是全身性进展，从而导致高死亡率。已知几种质粒编码的毒力基因是生存和发病机制所必需的，但染色体基因的作用在很大程度上尚未得到探索。本研究首次深入努力表征和确定胃内感染后在淋巴组织中表达的耶尔森氏菌染色体基因的功能。从经胃内感染并用氯霉素（Cm）处理的小鼠派尔集合淋巴结组织中分离出在宿主中表达带有cat融合基因的菌株；以这种方式鉴定的基因被命名为hre，即宿主反应元件。鉴定出在体内（在小鼠组织中）对Cm耐药而在体外（在26摄氏度的实验室培养基上）对Cm敏感的hre::cat菌株，并显示其由61个不同的等位基因组组成。对48个等位基因组的hre::cat融合基因进行了克隆，并通过DNA序列分析进行了表征。结果鉴定出了铁摄取、抵御环境压力、细胞膜成分生物合成及其他多种代谢活动所必需的基因。然而，许多克隆的DNA序列与其他已知基因没有同源性。针对四个hre基因构建了插入突变体，并在小鼠模型中测试了所得小肠结肠炎耶尔森氏菌突变体对发病机制的影响。在宿主组织中进行生存测定和LD50分析时，所有突变菌株的毒力均受到影响。
