GENE EXPRESSION IN MYCOBACTERIUM TUBERCULOSIS

结核病是人类的一大祸害，是全世界因单一传染病而死亡的主要原因。尽管结核病的发病率在美国再次开始下降，但结核病在这个国家仍然是一个重大的健康问题，最常见的影响人群是老年人、无家可归者、艾滋病患者和来自结核病流行国家的移民。尽管结核病的病原体结核分枝杆菌在一个世纪前就已被发现，但关于结核分枝杆菌的基本生理能力、遗传学和致病性机制的知识直到现在才开始出现。我们已经鉴定出几个基因，当结核分枝杆菌在培养的人巨噬细胞中生长时，这些基因在结核分枝杆菌H37Rv中表达，而在实验室培养液中生长时，这些基因在结核分枝杆菌H37Rv中不表达。我们推测这些基因及其产物可能在巨噬细胞中结核分枝杆菌的生存和生长中起重要作用，并可能参与结核杆菌的致病性。我们建议(1)通过对巨噬细胞中协调表达的cosmid基因（一个推定的应答调节基因）和mceD基因（一个已被证明能提高培养巨噬细胞中大肠杆菌存活的基因）上的基因进行分子和遗传表征，确定巨噬细胞表达的特定基因产物对巨噬细胞中结核分枝杆菌存活和生长的贡献；(2)鉴定和表征结核分枝杆菌在吞噬后早期、晚期和培养的人巨噬细胞生长过程中表达的基因和基因产物。

Tuberculosis, one of the great scourges of humankind, is the leading cause of death worldwide from a single infectious disease. Although the incidence of TB has again begun to decline in the U.S., TB remains a significant health problem in this country, most frequently affecting the elderly, the homeless, individuals with AIDS and immigrants from nations where TB is endemic. Although the causative agent of TB, Mycobacterium tuberculosis, was identified a century ago, knowledge about fundamental physiological capabilities, the genetics and the mechanisms of pathogenicity of M. tuberculosis is only now beginning to emerge. We have identified several genes which are expressed by M. tuberculosis H37Rv when the bacilli are growing in human macrophages in culture, but which are not expressed by the bacilli when they are growing in laboratory broth culture. We hypothesize that these genes and their products may be important in the survival and growth of M. tuberculosis in macrophages and may contribute to the pathogenicity of the tubercle bacilli. We propose to (1) determine the contribution of specific macrophage-expressed gene products to survival and growth of M. tuberculosis in macrophages by molecular and genetic characterization of genes on a cosmid that appear to be coordinately expressed, a putative response regulator gene, and mceD, a gene that has been shown to enhance survival of E. coli in cultured macrophages; and (2) to identify and characterize genes and gene products of M. tuberculosis that are expressed at early times after phagocytosis, at late times, and throughout growth in human macrophages in culture.