Characterization of hypochlorous acid as potent physiological antimicrobial

病原菌的入侵引发宿主机体多种防御机制。哺乳动物宿主防御系统的细胞采用的一种非常有效的策略涉及产生高水平的次氯酸（HOCl），这是家用漂白剂的有效成分，也是一种众所周知的高效消毒剂。中性粒细胞利用hocl的产生来杀死入侵的微生物，屏障上皮细胞也利用hocl的产生来控制细菌的定植。最近的研究表明，HOCl导致细菌中无数必需蛋白质的氧化展开、失活和聚集，为漂白剂杀死细菌的机制提供了第一个线索。细菌似乎已经进化出了保护自己免受hocl压力的重要策略，使它们能够在宿主组织中定植并引起感染。初步研究表明，尿路致病性大肠杆菌（UPEC）菌株CFT073，一种以参与尿路感染而闻名的菌株，比共生实验室大肠杆菌菌株对hocl压力的抵抗力强得多。此外，UPEC菌株具有形成生物膜的能力，保护它们免受自然宿主防御系统的侵害，并进一步提高对HOCl的抵抗力。本研究的目的是鉴定和表征选定的upec特异性基因，这些基因有助于CFT073在浮游状态和/或生物膜中增强对hocl的抗性。我们认为，降低CFT073对hocl的耐药性，必然会降低其致病性。我将对选定的upec特异性基因产物进行生化表征，这些基因产物对CFT073的漂白剂抗性贡献最大，并通过使用适当的突变菌株确定它们在hocl胁迫下的体内作用。通过在尿路感染模型中使用各自的缺失突变体，我们将揭示哪些upec特异性基因产物是CFT073致病性所必需的。这些蛋白质将成为未来小型化合物筛选的靶标。总之，我将使用多方面的生化和遗传学方法来详细了解细菌如何响应和防御HOCl，并制定长期目标，以提高致病菌对HOCl的敏感性。

Invasion of pathogenic bacteria elicit multiple defense mechanisms in host organisms. One very potent strategy that cells of the mammalian host defense system employ involves the production of high levels of hypochlorous acid (HOCl), the active ingredient of household bleach and a well-known, highly effective disinfectant. HOCl-production is used by neutrophils to kill off invading microorganisms, as well as by cells of barrier epithelia to control bacterial colonization. Recent studies demonstrated that HOCl causes the oxidative unfolding, inactivation and aggregation of countless essential proteins in bacteria, providing a first clue as to the mechanism by which bleach kills bacteria. Bacteria appear to have evolved vital strategies to protect themselves against HOCl-stress, allowing them to colonize host tissues and cause infections. Preliminary studies revealed that the uropathogenic E. coli (UPEC) strain CFT073, a strain known for its involvement in urinary tract infections, is substantially more resistant to HOCl-stress than commensal lab E. coli strains. Moreover, UPEC strains have the ability to form biofilms, which shield them against natural host defense systems, and further increase HOCl resistance. Aim of this study is now to identify and characterize selected UPEC-specific genes, which contribute to the enhanced HOCl-resistance of CFT073 in the planktonic state and/or in biofilms. We reason that by decreasing the HOCl-resistance of CFT073, we will inevitably decrease its pathogenicity. I will biochemically characterize selected UPEC-specific gene products, which contribute most strongly to the bleach resistance of CFT073, and determine their in vivo role during HOCl-stress by using the appropriate mutant strains. By using the respective deletion mutants in a urinary tract infection model, we will reveal which UPEC-specific gene products are essential for CFT073 pathogenicity. These proteins will serve as targets for future small compound screens. In summary, I will use a multifaceted biochemical and genetic approach to obtain a detailed understanding about how bacteria respond to and defend themselves against HOCl with the long-term goal to develop strategies that increase the sensitivity of pathogenic bacteria to HOCl.