Derzelle Sylviane, Turlin Evelyne, Duchaud Eric, Pages Sylvie, Kunst Frank, Givaudan Alain, Danchin Antoine
Unité de Génétique des Génomes Bactériens. Laboratoire de Génomique des Microorganismes Pathogènes, Institut Pasteur, 75724 Paris, France.
J Bacteriol. 2004 Mar;186(5):1270-9. doi: 10.1128/JB.186.5.1270-1279.2004.
Photorhabdus luminescens is a symbiont of entomopathogenic nematodes. Analysis of the genome sequence of this organism revealed a homologue of PhoP-PhoQ, a two-component system associated with virulence in intracellular bacterial pathogens. This organism was shown to respond to the availability of environmental magnesium. A mutant with a knockout mutation in the regulatory component of this system (phoP) had no obvious growth defect. It was, however, more motile and more sensitive to antimicrobial peptides than its wild-type parent. Remarkably, the mutation eliminated virulence in an insect model. No insect mortality was observed after injection of a large number of the phoP bacteria, while very small amounts of parental cells killed insect larvae in less than 48 h. At the molecular level, the PhoPQ system mediated Mg(2+)-dependent modifications in lipopolysaccharides and controlled a locus (pbgPE) required for incorporation of 4-aminoarabinose into lipid A. Mg(2+)-regulated gene expression of pbgP1 was absent in the mutant and was restored when phoPQ was complemented in trans. This finding highlights the essential role played by PhoPQ in the virulence of an entomopathogen.
发光光杆状菌是昆虫病原线虫的共生菌。对该生物体基因组序列的分析揭示了PhoP-PhoQ的一个同源物，PhoP-PhoQ是一种与细胞内细菌病原体毒力相关的双组分系统。已证明该生物体对环境中镁的可利用性有反应。在该系统调节成分（phoP）中具有敲除突变的突变体没有明显的生长缺陷。然而，与野生型亲本相比，它的运动性更强，对抗菌肽更敏感。值得注意的是，该突变消除了在昆虫模型中的毒力。注射大量phoP细菌后未观察到昆虫死亡，而极少量的亲本细胞在不到48小时内就杀死了昆虫幼虫。在分子水平上，PhoPQ系统介导脂多糖中镁离子依赖的修饰，并控制将4-氨基阿拉伯糖掺入脂质A所需的一个基因座（pbgPE）。突变体中不存在镁离子调节的pbgP1基因表达，当phoPQ通过反式互补时，该表达得以恢复。这一发现突出了PhoPQ在昆虫病原体毒力中所起的重要作用。
