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首页> 外文期刊>Infection and immunity >Characterization of a new region required for macrophage killing by Legionella pneumophila.
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Characterization of a new region required for macrophage killing by Legionella pneumophila.

机译：表征嗜肺军团杆菌杀死巨噬细胞所需的新区域。

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In a previous study, a collection of 55 Legionella pneumophila mutants defective for macrophage killing was isolated by transposon mutagenesis. In this study, nine of these mutants that belong to the same DNA hybridization group (group 3) were characterized. A wild-type DNA fragment that covers this DNA hybridization group was cloned and sequenced. This region was found to contain six new genes (designated icmT, icmS, icmR, icmQ, icmP, and icmO), five of which contain at least one transposon insertion. No transposon insertion was found in icmS. However, this gene was found to be required for macrophage killing, since a kanamycin resistance cassette introduced into icmS by gene replacement resulted in a mutant that was attenuated for macrophage killing. A plasmid containing the DNA fragment that covers this region complements all the mutants for macrophage killing, although various levels of complementation were observed for mutants in different genes. Complementation tests were also performed with plasmids containing one or two of these genes, as well as with plasmids containing nonpolar in-frame deletions. The results from these complementation tests indicated that all six genes located in this region are needed for macrophage killing and that they are probably arranged as two transcriptional units (icmTS and icmPO) and two genes (icmR and icmQ). A region upstream of the coding sequence of several icm genes may contain a potential promoter and/or regulatory site. Homology searches show that icmP and icmO bear significant homology to the trbA and trbC genes from the Salmonella R64 plasmid, respectively. The sequences of the other four genes do not show significant homology with any entries in sequence databases.
机译：在以前的研究中，通过转座子诱变分离了55种嗜杀军团菌的突变体，这些突变体对巨噬细胞的杀伤具有缺陷。在这项研究中，表征了属于同一DNA杂交组（第3组）的9个突变体。覆盖该DNA杂交组的野生型DNA片段被克隆并测序。发现该区域包含六个新基因（指定为icmT，icmS，icmR，icmQ，icmP和icmO），其中五个包含至少一个转座子插入。在icmS中未发现转座子插入。但是，发现该基因是巨噬细胞杀伤所必需的，因为通过基因置换引入icmS的卡那霉素抗性盒会导致突变体，对巨噬细胞杀伤作用减弱。含有覆盖该区域的DNA片段的质粒与所有突变体互补以杀死巨噬细胞，尽管在不同基因中观察到了各种水平的互补。还用含有一个或两个这些基因的质粒以及含有非极性框内缺失的质粒进行互补测试。这些互补试验的结果表明，位于该区域的所有六个基因都是巨噬细胞杀死所必需的，它们可能被安排为两个转录单位（icmTS和icmPO）和两个基因（icmR和icmQ）。几个icm基因编码序列上游的区域可能包含潜在的启动子和/或调节位点。同源性搜索显示，icmP和icmO分别与沙门氏菌R64质粒的trbA和trbC基因具有显着同源性。其他四个基因的序列与序列数据库中的任何条目均未显示出显着同源性。

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