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

假单胞菌属和伯克霍尔德氏菌属是两组相关的革兰氏阴性细菌，它们通常存在于水、土壤和动植物表面。有些物种对人类和植物是致病的，有些会导致食品和工业腐败问题，而另一些则是有益的，促进植物生长，并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。铜绿假单胞菌产生毒力因子的军械库，并且对许多常规抗生素具有抗性，因此这种生物体的感染可能难以治疗，并且几乎不可能从囊性纤维化患者的肺部根除。诸如铜绿假单胞菌的细菌使用小的化学信号分子来协调细菌群体内的单个细胞的活动。这种细菌细胞间的通讯装置被称为群体感应（quorum sensing，QS）。铜绿假单胞菌使用至少两种化学上不同类别的QS信号分子，N-酰基高丝氨酸内酯（AHL）和2-烷基-4-喹诺酮（AQ）来控制毒力因子的产生，所述毒力因子使生物体能够对抗免疫系统并引起组织损伤和疾病。通过突变负责AQ（和阿勒）信号分子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目标。了解AQ-signaling如何在分子水平上发挥作用，将使我们能够开发新的策略来控制病原菌，如铜绿假单胞菌。在这个项目中，我们建议建立在我们以前的工作，以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-signaling是如何受到缺氧的影响，并发现AQs在清除铁中的作用（一种必需的细菌营养素）以及在应激条件下刺激一部分细菌群体的死亡，以使细菌群体整体受益。我们还计划将这些研究扩展到两种伯克霍尔德氏菌，植物伯克霍尔德氏菌和谷伯克霍尔德氏菌，它们可以引起人类感染，但主要是水稻的病原体。从我们对AQ-signaling的分子基础的理解，我们还将探索AQ-degrading酶用于控制假单胞菌和伯克霍尔德菌感染的潜力，并合成一系列AQs和AQ-precursor的类似物，这些类似物将被筛选为可能的新抗菌剂。因此，本研究将通过提供有用的科学工具，通过有助于理解基本生物系统以及通过设计和筛选用于预防和治疗假单胞菌和伯克霍尔德菌感染的新型抗菌剂而受益

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