2-Alkyl-4-quinolone signalling in Pseudomonas and Burkholderia

假单胞菌和伯克霍尔德氏菌是两个相关的革兰氏阴性菌群，广泛存在于水、土壤和动植物表面。一些物种对人类和植物是致病的，一些物种会造成食品和工业腐败问题，而另一些物种则是有益的，可以促进植物生长，可用于碳氢化合物和塑料的生物降解。该项目将主要关注铜绿假单胞菌，这是一种人类病原体，是医院患者感染的常见原因，也是囊性纤维化患者的主要问题。铜绿假单胞菌产生大量的毒力因子，对许多常规抗生素具有抗药性，因此感染这种微生物可能很难治疗，而且几乎不可能从囊性纤维化患者的肺中根除它。像铜绿假单胞菌这样的细菌使用小的化学信号分子来协调细菌种群中单个细胞的活动。这种细菌细胞间的通讯装置被称为群体感应(QS)。铜绿假单胞菌使用至少两类化学上不同的QS信号分子，N-酰基高丝氨酸内酯(AHLS)和2-烷基-4-喹诺酮(AQS)来控制毒力因子的产生，这些因子使有机体能够对抗免疫系统，导致组织损伤和疾病。通过突变负责AQ(和AHL)信号分子的产生和作用的基因使QS失活，使生物体不能引起感染。因此，QS系统是新抗菌剂的潜在靶点。在分子水平上了解AQ信号是如何工作的，将使我们能够开发新的策略来控制铜绿假单胞菌等病原菌。在这个项目中，我们建议在我们以前工作的基础上，更详细地了解铜绿假单胞菌如何合成AQ信号分子，AQS如何控制毒力因子的产生，AQ信号如何受到缺氧的影响，并发现AQS在清除铁(一种基本的细菌营养物质)以及在压力条件下刺激部分细菌种群死亡以造福于整个细菌种群方面的作用。我们还计划将这些研究扩展到两种伯克霍尔德氏菌，伯克霍尔德氏菌Plantarii和Burkholderia glumae，这两种细菌可以引起人类感染，但它们主要是水稻的病原体。根据对AQ信号分子基础的了解，我们还将探索AQ降解酶控制假单胞菌和伯克霍尔德氏菌感染的潜力，并合成一系列AQS和AQ-前体的类似物，这些类似物将被筛选为可能的新抗菌剂。因此，这项研究将有助于提供有用的科学工具，有助于了解基本的生物系统，并通过设计和筛选新的抗菌剂来预防和治疗假单胞菌和伯克霍尔德氏菌感染。

Pseudomonas and Burkholderia are two related groups of Gram-negative bacteria which are commonly found in water, soil and on the surfaces of plants and animals. Some species are pathogenic for human and plants, some cause food and industrial spoilage problems while others are beneficial and promote plant growth and can be used for biodegradation of hydrocarbons and plastics. This project will focus mainly on Pseudomonas aeruginosa, a human pathogen which is a common cause of infections in hospital patients and a major problem in individuals with cystic fibrosis. P. aeruginosa produces an armoury of virulence factors and is resistant to many conventional antibiotics and so infections with this organism can be difficult to treat and it is almost impossible to eradicate from the lungs of cystic fibrosis patients. Bacteria such as P. aeruginosa use small chemical signal molecules to co-ordinate the activities of the individual cells within the bacterial population. This bacterial cell-to-cell communication device is called quorum sensing (QS). P. aeruginosa uses at least two chemically distinct classes of QS signal molecules, the N-acylhomoserine lactones (AHLs) and the 2-alkyl-4-quinolones (AQs) to control production of virulence factors which enable the organism to combat the immune system and cause tissue damage and disease. Inactivation of QS by mutating the genes responsible for the production and action of the AQ (and AHL) signal molecules renders the organism incapable of causing infections. QS systems are therefore potential targets for new antibacterial agents. Understanding how AQ-signalling works at a molecular level will allow us to develop new strategies for controlling pathogenic bacteria such as P. aeruginosa. In this project we propose to build on our previous work to understand in more detail how P. aeruginosa synthesizes AQ signal molecules, how AQs control virulence factor production, how AQ-signalling is affected by a lack of oxygen and to discover the role of AQs in scavenging for iron (an essential bacterial nutrient) and in stimulating the death of a proportion of the bacterial population under stressful conditions for the benefit of the bacterial population as a whole. We also plan to extend these studies to two Burkholderia species, Burkholderia plantarii and Burkholderia glumae which can cause infections in humans but which are primarily pathogens of rice. From our understanding of the molecular basis of AQ-signalling, we will also explore the potential of AQ-degrading enzymes for controlling Pseudomonas and Burkholderia infections and synthesize a series of analogues of AQs and AQ-precursors which will be screened as possible new antibacterial agents. Thus this research will be of benefit by providing useful scientific tools, by contributing to the understanding of fundamental biological systems and by designing and screening novel antibacterial agents for the prevention and treatment of Pseudomonas and Burkholderia infections