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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Minimization of the Legionella pneumophila genome reveals chromosomal regions involved in host range expansion
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Minimization of the Legionella pneumophila genome reveals chromosomal regions involved in host range expansion

机译：嗜肺军团菌基因组的最小化揭示了参与宿主范围扩展的染色体区域

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摘要

Legionella pneumophila is a bacterial pathogen of amoebae and humans. Intracellular growth requires a type IVB secretion system that translocates at least 200 different proteins into host cells. To distinguish between proteins necessary for growth in culture and those specifically required for intracellular replication, a screen was performed to identify genes necessary for optimal growth in nutrient-rich medium. Mapping of these genes revealed that the L. pneumophila chromosome has a modular architecture consisting of several large genomic islands that are dispensable for growth in bacteriological culture. Strains lacking six of these regions, and thus 18.5% of the genome, were viable but required secondary point mutations for optimal growth. The simultaneous deletion of five of these genomic loci had no adverse effect on growth of the bacterium in nutrient-rich media. Remarkably, this minimal genome strain, which lacked 31% of the known substrates of the type IVB system, caused only marginal defects in intracellular growth within mouse macrophages. In contrast, deletion of single regions reduced growth within amoebae. The importance of individual islands, however, differed among amoebal species. The host-specific requirements of these genomic islands support a model in which the acquisition of foreign DNA has broadened the L. pneumophila host range.
机译：嗜肺军团菌是变形虫和人的细菌病原体。细胞内生长需要IVB型分泌系统，该系统能将至少200种不同的蛋白质转运到宿主细胞中。为了区分培养物中生长所需的蛋白质和细胞内复制特别需要的蛋白质，进行了筛选以鉴定在营养丰富的培养基中最佳生长所需的基因。这些基因的图谱显示，嗜肺乳杆菌染色体具有模块化的结构，该结构由几个大的基因组岛组成，这些岛对于细菌培养中的生长是必不可少的。缺少这些区域中的六个区域，因此占基因组的18.5％的菌株是可行的，但需要第二个点突变才能获得最佳生长。在富含营养的培养基中，同时删除五个这样的基因组位点对细菌的生长没有不利影响。值得注意的是，这种最小的基因组菌株缺乏IVB系统已知底物的31％，仅在小鼠巨噬细胞内的细胞内生长中仅引起边缘缺陷。相反，单个区域的缺失降低了变形虫内的生长。但是，在各个变形虫物种之间，各个岛屿的重要性有所不同。这些基因组岛对宿主的特定要求支持了一种模型，在该模型中，外源DNA的获得扩大了嗜肺乳杆菌的宿主范围。

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