ROLE OF A NEW SIGNAL MOLECULE IN P. AERUGINOSA VIRULENCE

铜绿假单胞菌是在医院获得性感染患者中发现的最普遍的革兰氏阴性细菌，在免疫功能低下和囊性纤维化患者中均产生高死亡率。这种机会致病菌产生一系列毒力因子，其中一些是由细胞密度监测机制如群体感应控制的。群体感应涉及一种信号分子，即自诱导剂，它随着细菌密度的增加而增加浓度，直到达到一个阈值浓度，它结合并激活转录激活蛋白。P. aeruginosa使用两种群体感应系统las和rhl，通过两种主要的自诱导剂3-oxo-C12-HSL和C4-HSL控制多种毒力因子（包括LasB弹性酶）。最近发现了第三种诱导剂分子，称为喹诺酮假单胞菌信号（PQS）。初步结果表明，PQS受最小群体感应系统的调控，诱导lasB至少需要Rh1R。为了阐明PQS的合成途径，g3ene表征了控制PQS表达的因子。为了阐明PQS前体——邻氨基苯甲酸酯（anthranilate）的合成途径，我们将研究其相关基因，并利用基于LasB产生的表型和表型筛选来克隆PQS的其他相关基因。为了确定PQS在铜绿假单胞菌毒力中的作用，将使用报告基因融合来确定PQS如何影响不同毒力基因的表达。最后，研究PQS的表达，或采用PQS生物测定法监测其在不同条件下的产量。本研究的长期目标是确定PQS在铜绿假单胞菌感染发病机制中的作用，希望它能导致新的有效的治疗铜绿假单胞菌的方法。

Pseudomonas aeruginosa is the most prevalent Gram negative bacteria found in patient with hospital-acquired infections and produces a high mortality rate in both immunocompromised and cystic fibrosis patients. This opportunistic pathogen produces an arsenal of virulence factors, some of which are controlled by the cell density monitoring mechanism as quorum sensing. Quorum sensing involves a signal molecule, the autoinducer, that builds in concentration with bacterial density until a threshold concentration is reached where it binds and activates a transcriptional activator protein. P. aeruginosa uses two quorum sensing systems, las and rhl, to control numerous virulence factors (including LasB elastase) through two primary autoinducers, 3-oxo-C12-HSL and C4-HSL. Recently a third inducer molecule designated as the Pseudomonas Quinolone Signal (PQS) was discovered. Preliminary results show that PQS is regulated by the las quorum sensing system and that it requires at least Rh1R to inducer lasB. To elucidate the PQS synthetic pathway, g3enes characterize factors controlling PQS expression. To elucidate pathway, genes responsible for anthranilate (a PQS precursor) synthesis will be studied, and a phenotypic, and a phenotypic screen based on LasB production will be used to clone other genes responsible for PQS production. To define the role of PQS in P. aeruginosa virulence, reporter gene fusions will be used to determine how PQS affects the expression of different virulence genes. Finally, to study PQS expression, or PQS bioassay will be used to monitor its production under various conditions. The long term goal of this proposal is to determine the role of PQS in the pathogenesis of P. aeruginosa infections with the hope it will lead to new and effective therapies against aeruginosa.