Investigating the molecular mechanisms underpinning the quorum sensing dependent regulation of key virulence descriptors in Yersinia spp

鼠疫耶尔森氏菌可能是造成人类死亡的最多的微生物。在第一次大爆发(大流行)期间，查士丁尼的鼠疫造成约8000万至1亿人死亡，而黑死病(约1348年至1351年)被认为导致居住在欧洲的2400万人中的三分之一至一半死亡。它作为病原体的“成功”归功于它的高度传染性，在短短1-2天内就会死亡。因此，耶尔森氏菌属在影响人类历史和文明的微生物学故事中占有突出的地位，可能比任何其他细菌都要大。在发达国家和第三世界地区，仍有暴发和随后的死亡，那里的感染表现为淋巴腺鼠疫、肺炎鼠疫或败血症鼠疫。如果不治疗，死亡率极高，对于原发性肺鼠疫，如果不治疗，死亡率可接近100%，如果使用适当的抗生素，死亡率可高达50%。由于任何特定时间的病例数量有限，人与人之间的肺鼠疫很少见，但传染性很强，10到100个细菌足以引起感染。感染也可以通过口服、皮内、皮下或静脉途径。由于鼠疫杆菌是一种使用次级哺乳动物和昆虫宿主的人畜共患传染病，因此传播大大加剧。小肠结肠炎耶尔森菌和假结核耶尔森菌(鼠疫杆菌最近进化而来)也是适应能力很强的人类主要病原体，与鼠疫杆菌引起的胃部感染不同，胃感染通常不是致命的。这三种细胞都拥有一种三型分泌系统(T3S)，它通过一种被称为注射体的大分子针状结构将效应蛋白输送到真核细胞的胞浆中，从而扰乱宿主细胞的信号系统，触发细胞骨架重排，诱导细胞凋亡。注射体的所有结构成分以及效应器都编码在一个毒力质粒上，其中表达受温度调节。这些人类病原体已经进化出复杂的分子网络，促进了环境和动物宿主之间的迁移，我们已经证明了耶尔森氏菌的群体感应细胞到细胞信号系统。调节一些与毒力相关的表型，包括运动性、生物膜形成、聚集、N-乙酰氨基葡萄糖代谢和T3S。这些毒性相关的表型代表了控制毒力的新靶点，这在多重抗药性鼠疫杆菌菌株重新出现的后果背景下尤其重要。含铁硫簇的蛋白质是一组具有一系列功能的调节器，包括感知分子氧、胁迫反应和铁调节。铁硫簇调节因子Iscr参与了一种稳态机制，在大肠杆菌和假结核杆菌中被认为调节Fe-S簇的生物发生。它已被证明通过T3S系统调节因子LcrF参与T3S系统的调节。鉴于QS和Iscr调节T3S系统，本项目将专注于研究将这三个系统联系在一起的分子调控机制。这项工作将使用假结核杆菌和鼠疫杆菌，该项目还将研究鼠疫杆菌在我们的秀丽线虫(线虫)、印鼠客蚤(东方鼠蚤)和人虫(人体虱子)模型系统中的反应。

Yersinia pestis is probably responsible for more human deaths than any other microorganism.During the first major outbreak (pandemic), the plague of Justinian, around 80-100 million peopledied whereas The Black Death (ca 1348-1351) is believed to have killed between 1/3 to 1/2 of the24 million people living in Europe. Its 'success' as a pathogen is attributed to the fact that it ishighly contagious and death can occur in as little as 1-2 days. The genus Yersinia thereforeoccupies a prominent place in the story of microbiology influencing human history and civilisationpossibly to a greater extent than any other bacterium. Outbreaks and subsequent deaths still occurin both developed and third world locations where infections present as bubonic, pneumonic orsepticaemic plague. Untreated, mortality rates are extremely high and in the case of primarypulmonary plague this can approach 100% if untreated, and up to 50 % following the use ofappropriate antibiotics. Person-to-person pneumonic plague is rare due to the limited number ofcases at any given time but is highly infectious with 10 to 100 bacteria being sufficient to causeinfection. Infection can also be through oral, intradermal, subcutaneous, or intravenous routes.Transmission is greatly exacerbated because Y. pestis is a zoonotic infection using secondarymammalian and insect hosts.Yersinia enterocolitica and Yersinia pseudotuberculosis (from which Y. pestis recently evolved) arealso highly adaptable primary human pathogens, which in contrast to Y. pestis cause gastricinfections which are usually non-lethal. All three possess a type three secretion (T3S) systemwhich delivers effector proteins into the cytosol of eukaryotic cells through a macromolecularneedle-like structure known as the injectisome causing disruption of host cell signalling systems,triggering cytoskeletal rearrangement and inducing apoptosis. All the structural components of theinjectisome, along with the effectors are encoded on a virulence plasmid where expression isregulated by temperature.These human pathogens have evolved sophisticated molecular networks that facilitate migrationbetween the environment and their animal hosts and we have shown that the quorum sensing cellto-cell signalling systems of Yersinia spp. regulates a number of virulence related phenotypesincluding motility, biofilm formation, aggregation, N-acetylglucosamine metabolism and T3S. Thesevirulence-related phenotypes represent novel targets for the control of virulence which is ofparticular importance in the context of the consequences of the re-emergence of a multi-drugresistant Y. pestis strain.Iron-sulphur cluster-containing proteins are a group of regulators with a range of functionsincluding sensing of molecular oxygen, stress response, and iron regulation. The iron sulphurcluster regulator IscR is involved in a homeostatic mechanism believed to regulate Fe-Scluster biogenesis in Escherichia coli and in Y. pseudotuberculosis it has been shown to beinvolved in the regulation of the T3S system via the T3S system regulator LcrF.Given that QS and IscR regulates the T3S system this project will focus on investigating themolecular regulatory mechanisms which link these three systems together. Y. pseudotuberculosisand Y. pestis will be used for this work and the project will also investigate the Y. pestis response inour Caenorhabditis elegans (nematode worm), Xenopsylla cheopis (oriental rat flea) and Pediculushumanus humanus (human body louse) model systems.