MOLECULAR AND FUNCTIONAL ANALYSES OF THE PMRA/PMRB REGULATORY SYSTEM

性状（由申请人提供）：革兰氏阴性菌的最外层是脂多糖（即LPS）。这种分子构成了保护细菌免受各种有害物质侵害的渗透性屏障，并且它被不同动物的宿主先天免疫系统识别，并被几种天然抗微生物肽靶向。许多革兰氏阴性病原体已经进化出以降低宿主识别并增加对抗菌肽和某些有毒金属的抗性的方式修饰其LPS的机制。在伤寒和胃肠炎的病原体肠道沙门氏菌中，许多LPS修饰仅在激活PmrA/PmrB调节系统的条件下观察到。该提案描述了旨在了解PmrA/PmrB系统的活性如何动态控制以响应内部和外部输入的实验。我们的研究将集中在一个新的基因，编码小肽和小RNA，并在一组沙门氏菌特异性基因，所需的生存在巨噬细胞内。此外，我们将分析PmrD蛋白在沙门氏菌中发挥的独特特性，在沙门氏菌中，它的功能是激活PmrA蛋白，在相关物种大肠杆菌中，它缺乏这种能力。我们将研究是否有能力的Escherosal E。大肠杆菌在小鼠肠道中定植的能力受到损害。大肠杆菌在促进沙门氏菌中这种激活的诱导条件下进行PmrA控制的LPS修饰。这些目标的实现将揭示PmrA/PmrB系统-肠道细菌中LPS修饰的主要调节因子-如何以保护其免受抗菌素损伤的方式控制其细胞表面的重塑。公共卫生相关性：细菌通常以改变其对抗菌剂的抗性的方式修饰其细胞表面。拟议的研究将揭示导致病原体肠道沙门氏菌和人类植物群大肠杆菌正常成员细胞表面决定簇差异控制的机制。

DESCRIPTION (provided by applicant): The outermost part of Gram-negative bacteria is the lipopolysaccharide (i.e. LPS). This molecule constitutes a permeability barrier that protects bacteria from a variety of noxious agents, and it is recognized by the host innate immune system of different animals and targeted by several natural antimicrobial peptides. Many Gram-negative pathogens have evolved mechanisms to modify their LPS in ways that decrease recognition by the host and increase resistance to antimicrobial peptides and certain toxic metals. In Salmonella enterica, which is the etiologic agent of typhoid fever and gastroenteritis, many of these LPS modifications are observed only under conditions that activate the PmrA/PmrB regulatory system. This proposal describes experiments aimed at understanding how the activity of the PmrA/PmrB system is dynamically controlled in response to internal and external inputs. Our studies will focus on a novel gene that encodes both a small peptide and small RNA, and on a set of Salmonella-specific genes that are required for survival inside macrophages. In addition, we will analyze the distinct properties that the PmrD protein plays in Salmonella, where it functions to activate the PmrA protein, and in the related species Escherichia coli, where it lacks this ability. We will examine whether the ability of commensal E. coli to colonize the mouse intestine is compromised when E. coli carries out the PmrA-controlled LPS modifications under inducing conditions that promote such activation in Salmonella. An accomplishment of these goals will uncover how the PmrA/PmrB system - a major regulator of LPS modifications in enteric bacteria - controls the remodeling of its cell surface in ways that protect it from antimicrobial insult. PUBLIC HEALTH RELEVANCE: Bacteria often modify their cell surface in ways that alter their resistance to antimicrobial agents. The proposed research will uncover the mechanisms that result in differential control of cell surface determinants in the pathogen Salmonella enterica and in the normal member of the human flora Escherichia coli.