Genes in the Yersinia pestis lifecycle

鼠疫耶尔森菌是鼠疫的病原体，鼠疫是一种影响许多不同哺乳动物物种的疾病。鼠疫是由跳蚤传播的，跳蚤在吸血过程中被感染，并通过胃肠道生物膜定植。当定居的昆虫以新宿主为食时，通常是啮齿动物，就会传播。从历史上看，啮齿动物中的动物流行病暴发曾引发鼠疫通过跳蚤传播到人群中，造成毁灭性后果。因此，鼠疫杆菌被认为是最致命的单一细菌病原体和大规模杀伤性武器。鼠疫杆菌是一种克隆性病原体，其基因组包含4012个染色体基因和3个毒力质粒。pCDI质粒编码III型分泌机，将Yop效应物递送到宿主免疫细胞中。这种基本的毒力策略受到两个环境信号的调节：温度变化，因为细菌从跳蚤（18-30°C）转移到哺乳动物（37°C），以及细胞外钙离子的下降，被认为是III型针复合物穿透宿主免疫细胞（LCR，低钙反应）。大多数毒力质粒上基因的功能已被揭示，但染色体基因及其对鼠疫杆菌独特生命周期的贡献知之甚少。将体外培养的鼠疫杆菌的转录组与跳蚤生物膜中的细菌和侵入大鼠腹腔的鼠疫杆菌进行了比较：214个基因在跳蚤肠道中特异性上调，而119个基因在大鼠腹腔中特异性表达。在这里，我们将研究在跳蚤肠道或大鼠腹腔中上调的未表征的鼠疫杆菌基因的功能。为此，我们分离出7,832个突变体，在鼠疫杆菌C092染色体上绘制了插入病灶。在未知orf、假设基因和小rna中发生病变的突变体将分析跳蚤定植、LCR、111型分泌和效应器易位到宿主免疫细胞中的缺陷。选择的突变体将分析黑死病的发病机制和这种疾病的组织病理学特征。蚤生物膜或鼠疫发病机制存在缺陷的突变体将进行生化研究，从而探索未知基因产物和小rna在鼠疫菌生命周期中的具体功能。

Yersinia pestis is the causative agent of plague, a disease that affects many different mammalian species. Plague is transmitted by fleas, which are infected during blood meals and colonized via a gastrointestinal biofilm. Transmission occurs when colonized insects feed on new hosts, typically rodents. Historically, epizootic outbreaks in rodents have triggered flea-born transmission of plague into human populations with devastating consequences. For this reason, Y. pestis is considered the single most virulent bacterial pathogen and weapon of mass destruction. Y. pestis is a clonal pathogen with a genome of 4,012 chromosomal genes and three virulence plasmids. The pCDI plasmid encodes the type III secretion machine for delivery of Yop effectors into host immune cells. This essential virulence strategy is regulated by two environmental signals: temperature shift, as bacteria are transferred from fleas (18-30°C) to mammals (37°C), and a drop in extracellular calcium ions, perceived as type III needle complexes penetrate host immune cells (LCR, low-calcium response). The functions of most genes on the virulence plasmids have been revealed, however very little is known about chromosomal genes and their contributions to the unique lifecycle of Y. pestis. The transcriptome of Y. pestis grown in vitro has been compared with bacteria in a flea biofilm and Y. pestis invading a rat bubo: 214 genes are specifically upregulated in the flea gut, whereas 119 genes are specifically expressed in the rat bubo. Here we will investigate the function of uncharacterized Y. pestis genes upregulated in either the flea gut or the rat bubo. Towards this goal, we have isolated 7,832 mutants with mapped insertional lesions on the Y. pestis C092 chromosome (PEST-Library). Mutants with lesions in unknown ORFs, hypothetical genes and small RNAs will be analyzed for defects in flea colonization, the LCR, type 111 secretion and effector translocation into host immune cells. Selected mutants will be analyzed for the pathogenesis of bubonic plague and the histopathological features of this disease. Mutants with defects in flea biofilm or plague pathogenesis will be subjected to biochemical studies, thereby exploring the specific functions of unknown gene products and small RNAs in the Y. pestis lifecycle.