Legionella pneumophila developmental cycle & virulence

嗜肺军团菌是一种原生动物的胞内寄生虫，生活在水生环境中。 当通过气雾剂传播给易感人群时，会产生一种名为 退伍军人症。这种疾病的传播总是单向的--从环境到人类， 尽管进行了30年的研究，但对这种疾病为什么不会在人与人之间传播的解释 还没有被提供。我们已经记录了基于细胞的感染模型的发育周期 营养细菌分化成囊状代谢休眠形式，具有很强的韧性和高度的休眠性。 有感染力。这些包囊对抗生素、洗涤剂和其他有毒物质的影响具有抵抗力，并且可以 在水源对健康构成危害的情况下长期坚持使用。以确定这些是否 包囊是军团病传播的罪魁祸首，我们提出以下目标：1)发展 原生动物和自来水中的感染模型以确定促进包囊的环境条件 形态发生，其子目标是(I)通过光学和电子显微镜跟踪形态发生；(I)记者 基因融合；(Iii)脉冲追逐放射性标记和蛋白质组谱；以及(Iv)评估包囊形态 对洗涤剂、杀生剂和抗生素的抵抗力；对阿米巴和A/J小鼠的传染性 巨噬细胞。2)在A/J小鼠气溶胶攻击模型中评估包囊的毒性；以及3) 原生动物、水和HeLa细胞的囊样形态特征：(I)双向凝胶蛋白质组图谱 对于独特的蛋白质，(Ii)包囊分级研究，以确定外膜、周质和 细胞膜和(Iii)使用基于突变的方法来研究发育调节基因 以及监管因素。我们预计，对浮游孢囊的继续研究将做出重大贡献 对其生物学、发病机制、持久性和传播性的新认识 退伍军人症。与人类健康相关。退伍军人症是一种迅速增长的健康风险 世界范围内，尤其是对老年人和免疫功能受损的人。从这些活动中获得的知识 研究应该导致改进检测和控制措施，以降低对人类的风险。这些 研究还应提供与其他机会性环境病原体相关的见解，包括 Oxiella、Burkholderia和分支杆菌的种类。

Legionella pneumophila (L. pneumophila) resides in aquatic habitats as an intracellular parasite of protozoa and when transmitted in aerosols to susceptible humans, produces an acute pneumonia known as Legionnaires' disease. Transmission of this disease is always one-way - from the environment to humans, and despite 30 years of research, an explanation for why this disease is not spread from person to person has not been offered. We have documented a developmental cycle in cell based infection models in which vegetative bacteria differentiate into cyst-like metabolically dormant forms that are resilient and highly infectious. These cysts are resistant to the effects of antibiotics, detergents and other toxic agents and can persist in water sources for extended periods where they present a health hazard. To determine if these cysts are responsible for transmission of Legionnaires' disease we propose the following aims: 1) To develop infection models in protozoa and in tap water to identify environmental conditions that promote cyst morphogenesis with sub aims of (i) tracking morphogenesis by light and electron microscopy; (i) by reporter gene fusions; (iii) pulse chase radiolabeling and proteome profiling and (iv)to assess cyst forms for resilience to detergents, biocides, and antibiotics; and infectiousness for amoebae and A/J mouse macrophages. 2) Assessment of virulence of cysts in an A/J mouse aerosol challenge model; and 3) To characterize the cyst like forms arising from protozoa,water and HeLa cells by (i) 2D gel proteome profiling for unique proteins, (ii)cyst fractionation studies to identify proteins of the outer membrane, periplasm and cytoplasmic membrane and (iii) use a mutation based approach to study developmentally regulated genes and regulatory factors. We anticipate that continued study of the planktonic cysts will contribute significant new knowledge to our understanding of the biology, pathogenesis, persistence and transmission of Legionnaires' disease. Relevance to human health. Legionnaires' disease is a rapidly growing health risk world wide, and especially for the elderly and immunocompromised. The knowledge gained from these studies should lead to improved detection and control measures that reduce the risk to humans. These studies should also provide insights relevant to other opportunistic environmental pathogens including oxiella, Burkholderia and species of Mycobacterium.