Peptide-Based Quorum Sensing Controlling Virulence in Bacillus anthracis

性状（由申请人提供）：炭疽芽孢杆菌是B的成员。包括B的蜡状菌群。cereus和B.苏云金杆菌三种细菌物种在核苷酸水平上共享>90%相同的基因组，但它们通过宿主特异性和/或疾病表现来区分。而B.苏云金杆菌主要是一种昆虫病原菌和B.蜡状芽孢杆菌引起人类非致死性食物中毒，B。炭疽感染（炭疽）在哺乳动物中是极其致命的。B.炭疽杆菌主要归因于它的两个质粒pXO 1和pXO 2，它们携带编码炭疽毒素的结构基因和参与合成聚-D-谷氨酸胶囊的基因。这些毒力质粒在典型的B分离株中是不存在的。cereus和B.苏云金杆菌然而，同样明显的是，毒性基因表达的调节机制在B中是不同的。炭疽病例如，已知PlcR是B中的主要毒力调节因子。cereus和B.苏云金杆菌，但在B中无功能。炭疽病是由于plcR中的无义突变。PlcR与PapR构成基于肽的群体感应系统，PapR作为前原肽产生，分泌并经蛋白水解加工成PapR的活性形式。在达到足够的细胞外浓度后，活性PapR被输入细胞，在其中它结合并激活PlcR，随后控制靶毒力基因的表达。到目前为止，基于肽的群体感应系统是否存在于B。炭疽是完全未知的。我们的初步研究结果强烈表明，B。炭疽菌具有一种尚未被表征的基于肽的群体感应系统，命名为AqsR和AqsP，即炭疽群体感应调节剂和肽，其似乎与PlcR-PapR不同。AqsR-AqsP的失活呈现B。在肺炭疽的小鼠模型中，炭疽杆菌减毒，表明AqsR-AqsP系统调节B中毒力相关基因的表达。炭疽病在拟议的研究中，我们将确定构成和控制AqsR-AqsP群体感应系统的遗传成分，并确定和表征AqsR/AqsP调节的毒力基因。这些目标的实现将使AqsR-AqsP群体感应成为B中一种新的毒力调节机制。炭疽病，推进我们对B的病理生理学的认识。炭疽病，并帮助制定更好的反炭疽战略。此外，因为完整的AqsR-AqsP在两个B中似乎是保守的。cereus和B.苏云金芽孢杆菌，本研究中获得的知识也将适用于B的生理。蜡状菌群。 公共卫生相关性：在炭疽芽孢杆菌中还没有证实存在基于肽的群体感应系统及其与毒力的相关性。在拟议的研究中实现的目标将定义一个新的群体感应系统的遗传组成部分，并建立这个调控系统如何控制B中的毒力基因表达。炭疽病这个项目的结果将促进我们对B的认识。炭疽病的病理生理学，并帮助制定更好的抗炭疽战略。

DESCRIPTION (provided by applicant): Bacillus anthracis is a member of the B. cereus group that includes B. cereus and B. thuringiensis. Three bacterial species share >90% identical genomes at the nucleotide level, but they are differentiated by host specificity and/or disease manifestation. Whereas B. thuringiensis is mainly an insect pathogen and B. cereus causes a nonlethal food poisoning in humans, B. anthracis infections (anthrax) are extremely lethal in mammals. The virulence of B. anthracis has been primarily attributed to its two plasmids pXO1 and pXO2, which carry the structural genes encoding the anthrax toxins and genes involved in the synthesis of the poly-D- glutamate capsule. These virulence plasmids are absent in typical isolates of B. cereus and B. thuringiensis. However, it is also evident that regulatory mechanisms for virulence gene expression are distinct in B. anthracis. PlcR, for example, has been known to be a master virulence regulator in B. cereus and B. thuringiensis, but is nonfunctional in B. anthracis due to a nonsense mutation in plcR. PlcR constitutes a peptide-based quorum sensing system with PapR, which is produced as a pre-propeptide, secreted and processed proteolytically into an active form of PapR. Upon reaching a sufficient extracellular concentration, the active PapR is imported into the cell, in which it binds and activates PlcR, subsequently controlling expression of target virulence genes. To date, whether a peptide-based quorum sensing system exists in B. anthracis is completely unknown. Results from our preliminary study strongly indicate that B. anthracis possesses an as-yet-uncharacterized peptide-based quorum sensing system, named AqsR and AqsP for Anthrax quorum sensing Regulator and Peptide, which appears to be distinct from PlcR-PapR. Inactivation of AqsR-AqsP renders B. anthracis attenuated in a murine model of pulmonary anthrax, suggesting that the AqsR-AqsP system regulates expression of virulence-related genes in B. anthracis. In proposed studies, we will identify genetic components constituting and controlling the AqsR-AqsP quorum sensing system, and identify and characterize AqsR/AqsP-regulated virulence genes. An accomplishment of these goals will establish the AqsR-AqsP quorum sensing as a new virulence regulatory mechanism in B. anthracis, advance our knowledge about the pathophysiology of B. anthracis, and help the development of better anti-anthrax strategies. Moreover, because an intact AqsR-AqsP appears to be conserved in both B. cereus and B. thuringiensis, knowledge obtained in this study will also be applicable to the physiology of the B. cereus group of bacteria. PUBLIC HEALTH RELEVANCE: Existence of a peptide-based quorum sensing system and its relevance for virulence have not been demonstrated in Bacillus anthracis. Achieving the goals in the proposed research will define the genetic components of a novel quorum sensing system and establish how this regulatory system controls virulence gene expression in B. anthracis. Results from this project will advance our knowledge about B. anthracis pathophysiology and help develop better anti-anthrax strategies.