Gene Expression Patterns and Lifestyles in Legionella

嗜肺军团菌是导致军团病和其他急性呼吸道疾病的革兰氏阴性细菌，它在广泛的吞噬宿主细胞中复制。在军团病期间，嗜肺性乳杆菌在肺泡巨噬细胞中复制。在环境中，它可以在一系列非同寻常的原生动物宿主中复制。嗜肺乳杆菌在原生动物中的复制被认为是在浮游和生物膜条件下都发生的。在社区获得性感染和医院感染暴发期间，生物膜被认为是有机体的主要来源。嗜肺性乳杆菌在如此广泛的环境环境中生存和繁殖的分子基础知之甚少。几位研究人员提出，嗜肺性乳杆菌经历了不同形式之间的发育转换 解释了观察到的生活方式变化的多样性。嗜肺乳杆菌全基因组序列和包含所有已知嗜肺乳杆菌基因、开放阅读框和基因间隔区的微阵列的可获得性将允许评估几种可能解释这些不同生理状态的假说。具体地说，我们建议：(1)检验嗜肺乳杆菌在细胞内生存和生长过程中伴随着离散事件的不同基因表达模式的假设；(2)检验以下假设：在感染后的不同时间将从人的巨噬细胞中分离RNA，并使用全基因组军团菌微阵列来确定军团菌基因表达的整体模式；(2)检验以下假设 不同的基因表达模式解释了观察到的轴向生长和原生动物生长的嗜肺乳杆菌之间的表型差异；将从原生动物生长的军团菌中分离出RNA，并将全球基因表达模式与在无菌介质中生长的军团菌以及暴露在环境胁迫下的军团菌进行比较；(3)检验在原生动物宿主存在下特定的基因表达模式促进含有军团菌生物膜的形成的假设； 将从含有生物膜的军团菌中分离出RNA，并将基因表达模式与浮游阶段的细菌进行比较；(4)开发模型网络，描述已检查的不同条件下的相关基因表达模式，以确定针对每种军团菌生活方式或环境条件的特定报告。

Legionella pneumophila, the gram-negative species that causes legionnaires' disease and other acute respiratory diseases, replicates within a wide range of phagocytic host cells. During legionnaires' disease, L. pneumophila replicates in alveolar macrophages. In the environment, it can replicate in an extraordinary range of protozoan hosts. Replication of L. pneumophila in protozoa is thought to occur in both planktonic and biofilm conditions. Biofilms are thought to be a primary source of the organism during outbreaks in both community-acquired and nosocomial infections. Little is known about the molecular basis for the ability of L. pneumophila to survive and multiply within such a wide range of environmental settings. Several investigators have proposed that L. pneumophila undergoes a developmental switch between distinct forms to account for the observed versatility in changing lifestyles. The availability of the complete L. pneumophila genome sequence and a microarray containing all known L. pneumophila genes, open reading frames and intergenic regions will permit the evaluation of several hypotheses that may account for these different physiologic states. In particular we propose to: (1) Test the hypothesis that distinct patterns of gene expression accompany discrete events during intracellular survival and growth of L. pneumophila; RNA from human macrophages will be isolated at various times after infection and the global pattern of Legionella gene expression will be determined using a whole genome Legionella microarray; (2)Test the hypothesis that distinct patterns of gene expression account for the observed phenotypic differences between axenically-grown and protozoan-grown L. pneumophila; RNA will be isolated from Legionella grown in protoza and the pattern of global gene expression will be compared to that of Legionella grown in axenic media as well as to Legionella that have been exposed to environmental stresses; (3) Test the hypothesis that specific patterns of gene expression in the presence of protozoan hosts promote the formation of Legionella-containing biofilms; RNA will be isolated from Legionella containing biofilms and the patterns of gene expression will be compared to the bacteria in the planktonic phase; (4) Develop model networks that describe relevant patterns of gene expression from the different conditions that have been examined to define specific reporters for each Legionella lifestyle or environmental condition.