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首页> 外文期刊>Journal of bacteriology >Characterization of a Legionella pneumophila relA Insertion Mutant and Roles of RelA and RpoS in Virulence Gene Expression
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Characterization of a Legionella pneumophila relA Insertion Mutant and Roles of RelA and RpoS in Virulence Gene Expression

机译：嗜肺军团菌relA插入突变体的表征以及RelA和RpoS在毒力基因表达中的作用

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To investigate the involvement of RelA in the regulation of Legionella pneumophila virulence, a deletion substitution was constructed in the relA gene. The relA knockout resulted in an undetectable level of ppGpp in the cells during the stationary phase, but the original level was restored when the relA gene product was supplied on a plasmid. The effect of the relA mutation was examined with two systems that are known to be expressed during the stationary phase in L. pneumophila. Pigment production was found to be dependent on the relA gene product, and only one-half as much pigment was produced by the relA mutant as by the wild-type strain. Flagellum gene expression was also found to be dependent on the relA gene product, as determined with a flaA::lacZ fusion. However, the relA gene product was found to be dispensable for intracellular growth both in HL-60-derived human macrophages and in the protozoan host Acanthamoeba castellanii. To determine the involvement of the relA gene product in expression of L. pneumophila genes required for intracellular growth (icm/dot genes), nine icm::lacZ fusions were constructed, and expression of these fusions in the wild-type strain was compared with their expression in relA mutant strains. Expression of only one of the icm::lacZ fusions was moderately reduced in the relA mutant strain. Expression of the nine icm::lacZ fusions was also examined in a strain containing an insertion in the gene that codes for the stationary-phase sigma factor RpoS, and similar results were obtained. We concluded that RelA is dispensable for intracellular growth of L. pneumophila in the two hosts examined and that both RelA and RpoS play minor roles in L. pneumophila icm/dot gene expression.
机译：为了调查RelA参与调节肺炎军团菌毒力，在 relA 基因中构建了一个缺失替代。 relA 敲除导致静止期细胞中无法检测到ppGpp的水平，但是当在质粒上提供 relA 基因产物时，原始水平得以恢复。用两个已知在 L固定期表达的系统检查了 relA 突变的作用。肺炎。发现色素的产生依赖于 relA 基因产物，并且 relA 突变体产生的色素只有野生型菌株产生的色素的一半。还发现鞭毛基因表达依赖于 relA 基因产物，通过 flaA :: lacZ 融合蛋白测定。但是，发现在HL-60衍生的人类巨噬细胞和原生动物宿主 Acanthamoeba castellanii 中， relA 基因产物对于细胞内生长都是必不可少的。要确定 relA 基因产物与 L的表达有关。胞内生长所需的嗜肺细胞基因（ icm / dot 基因），九个 icm :: lacZ 融合体的构建和表达将这些融合体在野生型菌株中的表达与在 relA 突变株中的表达进行了比较。在 relA 突变株中，仅一种 icm :: lacZ 融合体的表达适度降低。还在菌株中检测了九种 icm :: lacZ 融合蛋白的表达，该菌株在编码固定相sigma因子RpoS的基因中包含一个插入片段，得到了相似的结果获得。我们得出结论，RelA对于 L的细胞内生长是必不可少的。肺炎在两个宿主中得到证实，并且RelA和RpoS在 L中均起较小作用。肺炎支原体icm / dot 基因表达。

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