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Expression of Legionella pneumophilaVirulence Traits in Response to Growth Conditions

机译:应对生长条件的嗜肺军团菌致病力表达

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In nature, Legionella pneumophila replicates exclusively as an intracellular parasite of amoebae, but it also persists in the environment as a free-living microbe. Studies of how this opportunistic pathogen recognizes and responds to distinct extracellular and intracellular environments identified a link between the growth phase and expression of traits previously correlated with virulence. When cultured in broth, only post-exponential-phase L. pneumophila was sodium sensitive, cytotoxic, osmotically resistant, competent to evade macrophage lysosomes, infectious, and motile. Likewise, the L. pneumophila phenotype changed during growth in macrophages. During the intracellular replication period, this bacterium was sodium resistant and lacked flagella; concomitant with macrophage lysis, L. pneumophilabecame sodium sensitive and flagellated. Expression of the virulent phenotype was a response to starvation, since exponential-phaseL. pneumophila became cytotoxic, sodium sensitive, and motile after incubation in broth from stationary-phase cultures, except when it was supplemented with amino acids. Together, these data indicate that while nutrients are plentiful, intracellularL. pneumophila organisms are dedicated to replication; when amino acids become limiting, the progeny express virulence factors to escape the spent host, to disperse and survive in the aquatic environment, and to reestablish a protected intracellular niche favorable for growth.
机译:在自然界中,嗜肺军团菌(Legionella pneumophila)仅作为变形虫的胞内寄生虫复制,但在环境中仍以自由生存的微生物的形式存在。关于这种机会病原体如何识别和响应不同的细胞外和细胞内环境的研究确定了生长阶段和以前与毒力相关的性状表达之间的联系。当在肉汤中培养时,仅指数后期 L。嗜肺细胞对钠敏感,具有细胞毒性,抗渗透性,能够逃避巨噬细胞溶酶体,具有传染性和运动能力。同样, L。巨噬细胞生长过程中嗜肺菌的表型发生变化。在细胞内复制期间,这种细菌耐钠,缺乏鞭毛。伴随巨噬细胞溶解, L。肺炎变为钠敏感和鞭毛虫。自指数期以来,毒性表型的表达是对饥饿的反应。在补充固定氨基酸的肉汤中培养后,嗜肺细胞变得细胞毒性,对钠敏感并能运动。总之,这些数据表明,虽然营养丰富,但细胞内的L却很高。嗜肺菌生物致力于复制;当氨基酸变得有限时,后代会表达毒力因子,以逃避用过的宿主,在水生环境中分散和生存,并重建对生长有利的受保护细胞内生态位。

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