ECF Sigma Factors and the Cell Envelope Stress Response of Clostridium difficile

描述（由申请人提供）：艰难梭菌是医院获得性感染性腹泻的最常见原因，仅在美国每年的费用就超过11亿美元。尽管C. difficile，目前尚不清楚C.艰难梭菌定殖于宿主并逃避宿主的免疫防御。一些证据表明先天免疫系统的抗菌肽在控制C.艰难感染。然而C.艰难梭菌对由抗微生物肽引起的应激的反应知之甚少。缺乏了解的一个主要原因是无法从基因上操纵这种严格的厌氧菌。我们已经成功地构建了稳定的靶向突变C。很难我们的长期目标是更好地了解C。艰难梭菌在感染期间抵抗先天免疫防御。细胞质外功能因子是一类重要的细胞膜应激信号转导系统。尽管ECF因子参与革兰氏阴性病原体对先天免疫防御的抗性，但ECF因子在革兰氏阳性病原体引起的感染期间的作用尚未确定。本申请的目的是确定ECF σ因子在C.并确定这些ECF σ因子如何影响梭菌的毒力特性。很难初步证据表明，C。艰难梭菌基因组编码响应于细胞包膜应激而诱导的三种ECF σ因子。ECF σ因子在抵抗细胞被膜应激和发病机制中的作用1）确定PrsW如何控制C.艰难梭菌ECF因子CsfT和CsfU;艰难梭菌ECF因子在细胞膜应激抵抗和发病机制中的作用;艰难ECF因子。拟议的研究与NIH的使命有关，因为它有望推进我们对这种日益重要的临床革兰氏阳性病原体如何抵抗细胞包膜应激和宿主先天免疫防御的认识。更好地了解细胞包膜应激反应可能为治疗C。艰难感染。

DESCRIPTION (provided by applicant): Clostridium difficile is the most common cause of hospital-acquired infectious diarrhea, at a cost of greater than 1.1 billion dollars per year in the United States alone. Despite the clinical impact of C. difficile it remains unclear how C. difficile colonizes the host and evades the host immune defenses. Several lines of evidence suggest antimicrobial peptides of the innate immune system play an important role in controlling C. difficile infections. However how C. difficile responds to the stress caused by antimicrobial peptides is poorly understood. One major reason for this lack of understanding is the inability to genetically manipulate this strict anaerobe. We have successfully constructed stable targeted mutations in C. difficile. Our long-term goal is to better understand how C. difficile resists the innate immune defenses during an infection. Extra-Cytoplasmic Function (ECF) factors represent an important class of signal transduction systems which respond to cell envelope stresses. Although ECF factors are involved in resistance to innate immune defenses in Gram- negative pathogens, the role of ECF factors during infections caused by Gram-positive pathogens has not been established. The objective of this application is to define the role of ECF sigma factors in the cell envelope stress response of C. difficile and determine to how these ECF sigma factors contribute to the virulence properties of C. difficile. Preliminary evidence suggests the C. difficile genome encodes three ECF sigma factors which are induced in response to cell envelope stress. The role of ECF sigma factors in resistance cell envelope stress and pathogenesis C. difficile will be determined in the following specific aims: 1) Determine how PrsW controls expression of the C. difficile ECF factors CsfT and CsfU, 2) Define the role of these C. difficile ECF factors in resistance to cell envelope stress and pathogenesis, and 3) Identify the regulons of these C. difficile ECF factors. The proposed research is relevant to the mission of the NIH because it is expected to advance our knowledge of how this increasingly clinically important Gram-positive pathogen resists cell envelope stress and host innate immune defenses. A better understanding of the cell envelope stress response may provide new targets for treatment of C. difficile infections.