Mechanisms of Clostridium difficile spore germination

 描述(由申请人提供)：艰难梭菌是医院和长期保健机构中抗生素相关性腹泻的主要原因。除了患者死亡外，艰难梭菌感染给美国医疗体系带来的治疗相关成本估计为32亿美元。尽管艰难梭菌在美国的感染率正在上升，但令人惊讶的是，人们对艰难梭菌的致病机制知之甚少。艰难梭菌被认为是由宿主以休眠孢子的形式获得的。为了致病，孢子必须在胃肠道对触发萌发的信号做出反应，从而允许作为营养细菌生长、产生毒素和随后的孢子形成，然后才能排泄到环境中。我们已经证明，牛磺胆酸，一种通常在胃肠道中发现的胆汁酸，和甘氨酸是艰难梭菌孢子的共生菌。另一种胆汁酸，鹅去氧胆酸，抑制牛磺胆酸介导的萌发，对艰难梭菌的繁殖性生长有毒性。我们最近确定了艰难梭菌孢子上胆汁酸的分子靶标，从而确定了艰难梭菌孢子萌发的第一个受体。我们的长期目标是了解艰难梭菌萌发的分子机制，并利用这些知识合理设计艰难梭菌感染的抑制剂。在这一应用中，我们建议：(1)确定艰难梭菌孢子萌发受体与胆汁酸的相互作用；(2)确定艰难梭菌孢子中结合伙伴和萌发受体的超微结构位置；(3)确定CSPC将胆汁酸信号传递给初始孢子萌发；以及(4)识别其他艰难梭菌萌发受体。本文概述的实验的成功完成将扩大我们对艰难梭菌萌发机制的理解，为艰难梭菌孢子形成和孢子萌发的研究开辟新的途径，并导致在其他芽胞形成细菌中鉴定新发现的萌发受体的同源物(打开其他研究途径)。

 DESCRIPTION (provided by applicant): Clostridium difficile is the leading cause of antibiotic-associated diarrhea in the hospital and long term health care settings. In addition to the patient toll, the treatment-associated costs of C. difficile infections to the United States healthcare system have been estimated at $3.2 billion. Although the rate of C. difficile infection in the United States is rising, surprisingly little is known about the mechanisms of C. difficile pathogenesis. C. difficile is believed to be acquired by the host in the form of a dormant spore. To cause disease, the spore must respond in the gastrointestinal tract to signals that trigger germination, thereby allowing growth as a vegetative bacterium, toxin production and subsequent spore formation before excretion into the environment. We have shown that taurocholic acid, a bile acid normally found in the GI tract, and glycine are co-germinants for C. difficile spores. Another bile acid, chenodeoxycholic acid, inhibits taurocholic acid-mediated germination and is toxic for C. difficile vegetative growth. We recently identified the molecular target of bile acids on the C. difficile spore thus identifying the first C. difficile spore germinnt receptor. Our long-term goal is to understand the molecular mechanisms of C. difficile germination and use that knowledge to rationally design inhibitors of C. difficile infection. In ths application, we propose to: (1) identify how the C. difficile spore germinant receptor interacts with bile acids; (2) identify binding partners and the ultrastructural location of the germinant receptor in the C. difficile spore; (3) determine who CspC transmits the bile acid signal to initiae spore germination; and (4) identify other C. difficile germinant receptors. Successful completion of the experiments outlined herein will extend our understanding of the mechanisms of C. difficile germination, open new avenues in the study of C. difficile spore formation and spore germination and lead to the identification of homologs of the newly discovered germinant receptors in other spore-forming bacteria (opening other avenues of investigation).