Host cell killing and bacterial conjugation require overlapping sets of genes within a 22-kb region of the Legionella pneumophila genome
Host cell killing and bacterial conjugation require overlapping sets of genes within a 22-kb region of the Legionella pneumophila genome
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DOI：
10.1073/pnas.95.4.1669
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发表时间：
1998-02-17
影响因子：
11.1
通讯作者：
Shuman, HA
中科院分区：
文献类型：
--
作者：
Segal, G;Purcell, M;Shuman, HA
描述了嗜肺军团菌的一个22-kb DNA位点，其含有18个基因，其中16个是巨噬细胞杀伤所需的（icm基因）。本文通过发现位于两个icm基因座之间的五个基因，将两个先前描述的icm基因座连锁起来。新描述的基因中有四个是巨噬细胞杀伤（icmMLKE）所需的，一个是p53。16个icm基因似乎被组织为6个单独的基因（icmR、icmQ、icmG、icmC、icmD和icmF）和4个操纵子（icmTS、icmPO、icmMLKE和icmJB）。4个icm基因（icmP、icmO、icmL和icmE）显示出与参与接合的质粒基因的显著序列相似性，而发现其它icm基因与数据库条目不具有任何序列相似性。我们发现L.嗜肺菌能以每供体10（-3）至10（-4）的频率介导质粒DNA转移。在两个icm基因（icmT和icmR）中含有无效突变的菌株显示接合频率和巨噬细胞杀伤严重降低。在其他四个icm基因中含有插入片段的菌株（icmF、icmE、icmC和dotA）显示在接合中具有不太严重的缺陷，其他11个icm基因中的突变对接合频率没有影响，我们目前不知道接合本身是否在巨噬细胞杀伤中起作用，可能是小质粒可以利用现有的分泌系统被动员，或者DNA转移是L.嗜肺菌
A 22-kb DNA locus of Legionella pneumophila is described that contains 18 genes, 16 of which are required for macrophage killing (icm genes). In this paper two previously described icm loci were linked by the discovery of five genes located between the two loci. Four of the newly described genes are required for macrophage killing (icmMLKE) and one is dispensable. The 16 icm genes appeared to be organized as six individual genes (icmR, icmQ, icmG, icmC, icmD and icmF), and four operons (icmTS, icmPO, icmMLKE, and icmJB). Four icm genes (icmP, icmO, icmL, and icmE) show significant sequence similarity to plasmid genes involved in conjugation, whereas the other icm genes were found not to bear any sequence similarity to database entries. We found that L. pneumophila can mediate plasmid DNA transfer at a frequency of 10(-3) to 10(-4) per donor, Strains containing null mutations in two icm genes (icmT and icmR) showed a severe reduction in conjugation frequency and macrophage killing. Strains containing an insertion in four other icm genes (icmF, icmE, icmC, and dotA) were shown to have a less severe defect in conjugation, Mutations in the other 11 icm genes had no effect on conjugation frequency, We currently do not know whether conjugation itself plays a role in macrophage killing, It is possible either that small plasmids can take advantage of an existing secretion system to be mobilized or that DNA transfer is required for human macrophage killing by L. pneumophila.