Investigating bacterial virulence using an alternative host-pathogen model

使用替代宿主病原体模型研究细菌毒力

• 批准号: RGPIN-2014-04595
• 负责人: Charette, Steve
• 金额: $ 3.86万
• 依托单位: Université Laval
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2014
• 资助国家: 加拿大
• 起止时间: 2014-01-01 至 2015-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=566621
• 关键词: Investigating; bacterial; virulence; using; alternative

Virulence is defined as the ability of a bacterial pathogen to injure a host organism by producing factors that are essential for the pathogen to invade and multiply in the host. These factors must be identified and functionally characterized in order to understand the behaviour of bacterial pathogens. The long-term objective of my research program is to identify the molecular basis of the virulence factors produced by pathogenic bacteria affecting fish as well as ways to inhibit or modulate them to prevent or treat bacterial infections in fish farms. I use an approach that combines bacterial genomics with the use of the alternative host model Dictyostelium discoideum, a soil amoeba that is a natural predator of bacteria, to achieve this goal. D. discoideum is a particularly useful tool for studying the virulence of psychrophilic pathogenic bacteria, including those that affect fish such as salmonids. Over the next five years, my research program will continue to focus on the virulence of Aeromonas salmonicida. This bacterium is a fish pathogen that has a major negative impact on aquaculture in Canada. Using the amoeba host model, we have shown that this bacterium is sensitive to stressful conditions, which cause genomic modifications that affect major virulence factors, including the type three secretion system, leading to a loss of virulence. The genomic plasticity of A. salmonicida results from the presence of abundant mobile genetic elements in its genome. Using next generation sequencing and genotyping of multiple A. salmonicida strains, we have preliminary evidence of the presence of new uncharacterized virulence factors. Based on the hypothesis that important virulence factors of A. salmonicida are affected by the activity of mobile genetic elements, we propose that other virulence factors in this bacterium are also affected by the activity of mobile genetic elements and may be targets for the prevention or treatment of A. salmonicida infections. The identification and characterization of A. salmonicida virulence factors and the evaluation of their sensitivity to the direct effect of compounds isolated from natural products or through the action of mobile genetic elements stimulated by these compounds is a promising approach. My research program will thus focus on the following short-term objectives: (1) Identify new virulence factors of A. salmonicida by genetic screening using D. discoideum as a host and by comparative genomics. (2) Functionally characterize these new virulence factors using various approaches, including challenges in fish. This part of the study will also involve the development of new genetic tools to efficiently manipulate A. salmonicida genes. (3) Identify aquaculture-compatible compounds that directly inhibit virulence factors or disrupt their genes by stimulating mobile genetic elements. The effect of these compounds on A. salmonicida virulence will be screened using D. discoideum as a host. The most promising compounds will then be tested on fish. My research program will provide a better understanding of the virulence factors of A. salmonicida. Based on our on-going effort to understand the pathogenic basis of A. salmonicida and the objectives set out in this proposal, we are confident that we will be able to modulate and inhibit the virulence of this bacterium by taking advantage of its genomic plasticity. This research is crucial for the development of novel anti-bacterial drugs that target virulence factors and that can be used as alternatives to antibiotics not only in the veterinary field but also for human health.

毒力被定义为细菌病原体通过产生对病原体入侵和繁殖在宿主中至关重要的因素来损害宿主生物的能力。必须识别这些因素并在功能上表征，以了解细菌病原体的行为。我的研究计划的长期目标是确定影响鱼类的致病细菌产生的毒力因子的分子基础，以及抑制或调节它们以预防或治疗养鱼场中细菌感染的方法。我使用一种将细菌基因组学与替代宿主模型迪斯特尔迪斯特尔（Dictyostelium discoideum）的使用（一种天然细菌捕食者）的使用方法，以实现这一目标。 D. Discoideum是研究精神病致病细菌的毒力，包括影响鱼类等鱼类的毒力的特别有用的工具。在接下来的五年中，我的研究计划将继续专注于Salmonicida Aeromonas Salmonicida的毒力。该细菌是一种鱼病原体，对加拿大的水产养殖具有重大负面影响。使用变形虫宿主模型，我们表明该细菌对压力条件敏感，这会导致影响主要毒力因子（包括三型分泌系统）的基因组修饰，从而导致毒力丧失。 salmonicida的基因组可塑性是由于其基因组中存在丰富的移动遗传因素而产生的。使用下一代测序和多种salmonicida菌株的基因分型，我们有初步证据表明存在新的未表征的毒力因子。基于以下假设：salmonicida的重要毒力因子受移动遗传元素的活性影响，我们建议该细菌中的其他毒力因子也受移动遗传元素活性的影响，并且可能是预防或治疗salmonicida a链烟草感染的靶标。萨尔霉菌毒力因子的鉴定和表征及其对从天然产物分离的化合物的直接作用的敏感性或通过这些化合物刺激的移动遗传元素的作用是一种有希望的方法。因此，我的研究计划将重点放在以下短期目标上：（1）通过使用D. discoideum作为宿主和比较基因组学来确定salmonicida链球菌的新毒力因子。 （2）在功能上使用各种方法（包括鱼类的挑战）来表征这些新的毒力因子。该研究的这一部分还将涉及开发新的遗传工具，以有效操纵A. salmonicida基因。 （3）确定与水产养殖兼容的化合物，可直接抑制毒力因子或通过刺激移动遗传元素破坏其基因。这些化合物对salmonicida毒素的影响将使用D. Discoideum作为宿主进行筛选。然后，最有希望的化合物将在鱼类上进行测试。我的研究计划将更好地理解salmonicida的毒力因素。基于我们持续的努力了解萨尔霉菌的致病基础以及该提案中提出的目标，我们有信心通过利用其基因组可塑性来调节和抑制该细菌的毒力。这项研究对于靶向毒力因素的新型抗菌药物的开发至关重要，并且可以用作兽医领域的抗生素的替代方法，而且还可以用作人类健康。