Li Laam, Faucher Sébastien P
Department of Natural Resource Sciences, Faculty of Agricultural and Environmental Sciences, McGill University, Montréal, QC H9X 3V9, Canada.
Can J Microbiol. 2017 Jun;63(6):535-545. doi: 10.1139/cjm-2016-0780. Epub 2017 Mar 6.
The water-borne Gram-negative bacterium Legionella pneumophila (Lp) is the causative agent of Legionnaires' disease. Lp is typically transmitted to humans from water systems, where it grows inside amoebae. Survival of Lp in water is central to its transmission to humans. A transcriptomic study previously identified many genes induced by Lp in water. One such gene, lpg2524, encodes a putative LuxR family transcriptional regulator. It was hypothesized that this gene could be involved in the survival of Lp in water. Deletion of lpg2524 does not affect the growth of Lp in rich medium, in the amoeba Acanthamoeba castellanii, or in human macrophage-like THP-1 cells, showing that Lpg2524 is not required for growth in vitro and in vivo. Nevertheless, deletion of lpg2524 results in a faster colony-forming unit (CFU) reduction in an artificial freshwater medium, Fraquil, indicating that Lpg2524 is important for Lp to survive in water. Overexpression of Lpg2524 also results in a survival defect, suggesting that a precise level of this transcriptional regulator is essential for its function. However, our result shows that Lpg2524 is dispensable for survival in water when Lp is at a high cell density (10 CFU/mL), suggesting that its regulon is regulated by another regulator activated at high cell density.
水传播的革兰氏阴性菌嗜肺军团菌（Lp）是军团病的病原体。Lp通常从水系统传播给人类，它在变形虫体内生长。Lp在水中的存活是其传播给人类的关键。一项转录组学研究先前鉴定出Lp在水中诱导的许多基因。其中一个基因lpg2524编码一种假定的LuxR家族转录调节因子。据推测，该基因可能参与Lp在水中的存活。缺失lpg2524并不影响Lp在丰富培养基、在卡氏棘阿米巴中或在人巨噬细胞样THP-1细胞中的生长，表明Lpg2524在体外和体内生长中不是必需的。然而，在人工淡水培养基Fraquil中，缺失lpg2524会导致菌落形成单位（CFU）更快减少，这表明Lpg2524对Lp在水中存活很重要。Lpg2524的过表达也会导致存活缺陷，这表明这种转录调节因子的精确水平对其功能至关重要。然而，我们的结果表明，当Lp处于高细胞密度（10 CFU/mL）时，Lpg2524对于在水中存活是可有可无的，这表明其调控子由在高细胞密度下激活的另一种调节因子调控。
