Control of Flagellar Filament Length by FlaG in Polarly-Flagellated Bacterial Pathogens

FlaG 对极鞭毛细菌病原体鞭毛丝长度的控制

• 批准号: 10493413
• 负责人: DAVID R HENDRIXSON
• 金额: $ 20.5万
• 依托单位: UT SOUTHWESTERN MEDICAL CENTER
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-22 至 2024-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10493413
• 关键词: Bacteria; Biogenesis; Biological Models; Birds; Campylobacter jejuni; Cecum; Cell membrane; Cells; Data; Defect; Diffuse; Diffusion; Dimensions; Disease; Escherichia coli; Event; Filament; Flagella; Flagellin; Genetic Transcription; Impairment; Infection; Investigation; Knowledge; Length; Mastigophora; Modeling; Molecular; Molecular Chaperones; Molecular Structure; Motor; Mutation; Organelles; Organism; Outcome Study; Pathogenesis; Pathogenicity; Physiological; Polymers; Process; Production; Protein Secretion; Proteins; Pseudomonas aeruginosa; Resources; Rod; Salmonella; Sequence Homology; Structure; Surface; Swimming; Testing; Time; Type III Secretion System Pathway; Vibrio cholerae; Viscosity; base; cell motility; extracellular; host colonization; in vivo; migration; mutant; pathogen; pathogenic bacteria; periplasm; polymerization; self assembly

Project Summary Bacteria produce various macromolecular surface organelles that function in different processes. For many organelles, it is unclear how bacteria regulate their dimensions or even if a specific mechanism exists to govern the size or length of the organelle. The flagellum is a surface organelle that facilitates swimming motility and migration of pathogens to ideal niches in hosts to initiate infection and pathogenesis of disease. Two specific mechanisms have been discovered in flagellar biogenesis that regulate the length of the periplasmic rod and surface hook. However, a current hypothesis states that bacteria do not have a specific and active mechanism to regulate the length of the extracellular flagellar filament, which functions as the propeller of the flagellar motor and extends ~10 µm on the surface of model peritrichous bacteria such as Salmonella species and E. coli. Challenging this hypothesis are observations that many polarly-flagellated bacterial pathogens, such as Campylobacter jejuni, Vibrio cholerae, and Pseudomonas aeruginosa, produce flagellar filaments ~70% shorter than those of peritrichous bacteria. Furthermore, deletion of flaG that is conserved in these pathogens and many other polar flagellates but absent in peritrichous organisms, caused flagellar filaments to extend up to twice the length as those of WT cells. In addition, C. jejuni DflaG producing elongated flagellar filaments displayed a 28-fold defect for cecal colonization of the natural avian host, suggesting that properly regulating flagellar filament length is necessary for optimal colonization of a host. Together, these findings indicate that FlaG in polar flagellates is involved in a specific and active mechanism to control the extracellular length of the flagellar filament and is important for some pathogens to colonize hosts, but a molecular mechanism for how FlaG controls filament length is unknown. In this proposal, we will use C. jejuni as a model system for polar flagellates to understand how a bacterium employs FlaG to control the length of the flagellar filament by halting filament polymerization, an event that occurs at a large distance (~2-3 cell body lengths) from the bacterial surface. We will test two non-mutually exclusive hypotheses that FlaG controls flagellar filament length by the following mechanisms: 1) FlaG interfering with interactions between the filament-building flagellin subunits and the FliS chaperone to reduce flagellin secretion; and/or 2) FlaG functioning as a flagellin mimic to block flagellins from polymerizing into the filament at the tip of the flagellum. We will also investigate why production of elongated flagellar filaments by C. jejuni DflaG reduces the ability to colonize a host by analyzing the effects of elongated filaments on motility efficiency and velocity through different physiologically- relevant viscosities and secretion of proteins through the flagellum required for host interactions. Outcomes from this study will provide new knowledge regarding how bacteria control dimensions of macromolecular surface organelles to maintain proper function for host interactions and steps in pathogenesis of disease.

项目摘要 细菌产生各种大分子表面细胞器，在不同的过程中发挥作用。对于许多 细胞器，目前尚不清楚细菌如何调节其尺寸，甚至是否存在特定的机制， 控制着细胞器的大小和长度。鞭毛是促进游泳运动的表面细胞器 以及病原体迁移到宿主体内的理想小生境以引发感染和疾病的发病。两 在鞭毛生物发生中发现了调节周质长度的特殊机制 杆和表面钩。然而，目前的一种假说认为，细菌没有特异性和活性的 调节细胞外鞭毛丝长度的机制，其功能是推进器的螺旋桨。 鞭毛马达，并在模型周毛细菌（如沙门氏菌属）表面延伸约10 µ m 和e.杆菌支持这一假设的是观察到许多极鞭毛细菌病原体， 如空肠弯曲杆菌、霍乱弧菌和铜绿假单胞菌，产生鞭毛丝 比围毛型细菌短约70%。此外，在这些细胞中保守的flaG的缺失， 病原体和许多其他极性鞭毛虫，但没有在围毛生物，造成鞭毛丝， 延伸到WT细胞的长度的两倍。此外，C.空肠DflaG产生细长鞭毛 丝状体在天然鸟类宿主盲肠定殖中显示出28倍的缺陷，这表明， 调节鞭毛丝长度对于宿主的最佳定殖是必要的。总之，这些发现 表明FlaG在极性鞭毛虫中参与了一种特异的主动机制， 鞭毛丝的长度，并且对于一些病原体定殖宿主是重要的，但是分子 FlaG如何控制细丝长度的机制尚不清楚。在这个例子中，我们将使用C。空肠模型 极地鞭毛虫系统，了解细菌如何利用FlaG控制鞭毛虫的长度 通过停止细丝聚合来形成细丝，这是一个发生在很远距离（约2 - 3个细胞体长）的事件 从细菌表面。我们将测试两个不相互排斥的假设，即FlaG控制鞭毛 1）FlaG通过以下机制干扰增强的细胞间的相互作用， 鞭毛蛋白亚基和FliS伴侣蛋白以减少鞭毛蛋白分泌;和/或2）FlaG作为鞭毛蛋白发挥功能 模拟阻止鞭毛蛋白聚合成鞭毛尖端的细丝。我们亦会研究 为什么C.空肠DflaG通过以下方式降低定殖宿主的能力： 通过不同的生理学分析细长细丝对运动效率和速度的影响， 相关的粘度和分泌的蛋白质通过鞭毛所需的主机相互作用。成果 这项研究将提供关于细菌如何控制大分子尺寸的新知识。 表面细胞器，以维持宿主相互作用和疾病发病机制步骤的适当功能。