Host-induced Initiation of Clostridium difficile Sporulation

 描述(申请人提供)：艰难梭菌是一种主要的医院病原体，可引起高度传染性和难以治疗的严重腹泻疾病。艰难梭菌很容易传播，因为受感染的宿主会形成和排出传染性孢子。艰难梭菌的孢子形态对大多数消毒剂具有抵抗力，对于细菌在宿主外的生存至关重要。唯一已知的支持艰难梭菌孢子形成的自然环境是胃肠道，但我们对孢子形成的方式知之甚少。我们推测艰难梭菌的孢子形成是通过未知和独特的遗传机制，对宿主肠道内发现的信号做出反应。该项目的长期目标是发现触发艰难梭菌产孢量的肠道环境。这项应用的具体目标是确定孢子启动所需的遗传机制，并确定在寄主中如何启动孢子形成。利用我们以前在枯草杆菌芽胞形成、革兰氏阳性肠道致病机制和艰难梭菌分子遗传学方面的经验，我们将通过两个具体目标的详细实验来实现这些目标。首先，我们将揭示艰难梭菌孢子起始的遗传机制。 通过对产孢量缺陷突变体和新发现的早期产孢量调节因子的遗传分析。同时，我们将评估已确定的和可疑的孢子形成诱导化合物对孢子形成时间和频率的影响。本申请中提出的研究是创新的，因为它代表了作为艰难梭菌孢子起始的原型标准的孢子形成模式的背离，并试图揭示调节这种病原体的孢子形成的独特机制。这项拟议研究的预期贡献是详细了解孢子起始和寄主内孢子发育所需的基因。这一贡献意义重大，因为它是预防艰难梭菌形成孢子的策略发展的第一个STE。

 DESCRIPTION (provided by applicant): Clostridium difficile is a major nosocomial pathogen that causes severe diarrheal disease that is highly infectious and difficult to treat. C. difficileis easily transmitted due to the formation and expulsion of contagious spores from infected hosts. The spore form of C. difficile is resistant to most disinfectants and is critical for the survival f the bacterium outside of the host. The only natural environment known to support C. difficile spore formation is the gastrointestinal tract, yet we know very little about how spore formation occurs. We hypothesize that sporulation of C. difficile is initiated in response to signals found within the host intestine, through unknown and unique genetic mechanisms. The long-term goal of this project is to uncover the intestinal environment triggers C. difficile sporulation. The specific objectives of this application are to identify the genetic mechanisms required for spore initiation and determine how sporulation is initiated in the host. Capitalizing on our previous experience with Bacillus subtilis sporulation, Gram-positive intestinal pathogenesis and C. difficile molecular genetics, we will meet these objectives through the experiments detailed in two specific aims. First, we will reveal the genetic mechanisms of spore initiation in C. difficile through genetic analysis of sporulation-defective mutants and newly identified early sporulation regulators. In parallel, we will evaluate the effects of identified and suspected sporulation-inducing compounds on the timing and frequency of spore formation. The research proposed in this application is innovative because it represents a departure from the model sporulation paradigm as the archetypal standard for spore initiation by C. difficile and seeks to uncover the unique mechanisms that regulate sporulation in this pathogen. The expected contribution of the proposed research is a detailed understanding of the genes required for spore initiation and the development of spores within the host. This contribution is significant because it is the first ste in the development of strategies to prevent spore formation by C. difficile.