Institut Pasteur, Biologie des Bactéries Intracellulaires, CNRS URA 2171, Paris, France.
PLoS Genet. 2010 Feb 19;6(2):e1000851. doi: 10.1371/journal.pgen.1000851.
Legionella pneumophila and L. longbeachae are two species of a large genus of bacteria that are ubiquitous in nature. L. pneumophila is mainly found in natural and artificial water circuits while L. longbeachae is mainly present in soil. Under the appropriate conditions both species are human pathogens, capable of causing a severe form of pneumonia termed Legionnaires' disease. Here we report the sequencing and analysis of four L. longbeachae genomes, one complete genome sequence of L. longbeachae strain NSW150 serogroup (Sg) 1, and three draft genome sequences another belonging to Sg1 and two to Sg2. The genome organization and gene content of the four L. longbeachae genomes are highly conserved, indicating strong pressure for niche adaptation. Analysis and comparison of L. longbeachae strain NSW150 with L. pneumophila revealed common but also unexpected features specific to this pathogen. The interaction with host cells shows distinct features from L. pneumophila, as L. longbeachae possesses a unique repertoire of putative Dot/Icm type IV secretion system substrates, eukaryotic-like and eukaryotic domain proteins, and encodes additional secretion systems. However, analysis of the ability of a dotA mutant of L. longbeachae NSW150 to replicate in the Acanthamoeba castellanii and in a mouse lung infection model showed that the Dot/Icm type IV secretion system is also essential for the virulence of L. longbeachae. In contrast to L. pneumophila, L. longbeachae does not encode flagella, thereby providing a possible explanation for differences in mouse susceptibility to infection between the two pathogens. Furthermore, transcriptome analysis revealed that L. longbeachae has a less pronounced biphasic life cycle as compared to L. pneumophila, and genome analysis and electron microscopy suggested that L. longbeachae is encapsulated. These species-specific differences may account for the different environmental niches and disease epidemiology of these two Legionella species.
嗜肺军团菌和长滩军团菌是一种广泛存在于自然界中的大型细菌属的两个物种。嗜肺军团菌主要存在于自然和人工水路中，而长滩军团菌主要存在于土壤中。在适当的条件下，这两个物种都是人类病原体，能够引起一种严重的肺炎，称为军团病。在这里，我们报告了四个长滩军团菌基因组的测序和分析，其中一个是长滩军团菌 NSW150 血清群（Sg）1 的完整基因组序列，另外三个是属于 Sg1 的基因组序列和两个属于 Sg2 的基因组序列。四个长滩军团菌基因组的基因组组织和基因含量高度保守，表明适应生态位的压力很大。对长滩军团菌 NSW150 菌株与嗜肺军团菌的分析和比较显示了该病原体特有的共同但也出乎意料的特征。与宿主细胞的相互作用表现出与嗜肺军团菌不同的独特特征，因为长滩军团菌具有独特的潜在 Dot/Icm 型 IV 型分泌系统底物、真核样和真核结构域蛋白的 repertoire，并且编码额外的分泌系统。然而，分析长滩军团菌 NSW150 的 dotA 突变体在棘阿米巴属和小鼠肺部感染模型中的复制能力表明，Dot/Icm 型 IV 型分泌系统对于长滩军团菌的毒力也是必不可少的。与嗜肺军团菌不同，长滩军团菌不编码鞭毛，这为两种病原体在小鼠易感性方面的差异提供了一个可能的解释。此外，转录组分析表明，与嗜肺军团菌相比，长滩军团菌的两相生命周期不那么明显，基因组分析和电子显微镜观察表明长滩军团菌被囊封。这些种特异性差异可能解释了这两种军团菌在不同环境生态位和疾病流行病学方面的差异。
