Bacterial Iron Acquisition Strategies of Gram-Negative Bacteria from the Pasteurellaceae that Inhabit the Upper Respiratory Tract of Food Production Animals

我的研究项目包括表征食品生产动物重要革兰氏阴性细菌病原体中的铁获取系统，以及开发疾病预防疫苗。这个NSERC应用程序的重点是负责牛肉和奶牛的牛呼吸道疾病（BRD）的病原体。重要的BRD病原体（溶血Mannhemia haemolytica， Histophilus somni，多杀性巴斯德菌）在细菌细胞表面具有从宿主转铁蛋白中提取铁的表面受体，提供了独立于粘膜表面其他微生物增殖并引起侵袭性感染的能力。我们针对这些受体蛋白的疫苗策略是基于这样一个前提，即我们将消除BRD病原体增殖和引起侵袭性感染的能力，但不消除相关的共生物种。然而，我们目前对BRD病原体和相关共生菌株中铁获取基因的流行、多样性和交换的了解目前不足以衡量抗原变异的储存库和疫苗接种对上呼吸道微生物组的影响。因此，该计划的主要目标是确定：(i)铁获取基因的流行程度，（ii）遗传交换的效率，以及（ii）栖息在牛上呼吸道的巴氏杆菌科致病性和共生菌株和物种的功能性铁获取能力。我们将对微生物组样本、从微生物组样本中分离的细菌和BRD分离物中存在的铁获取基因的存在和多样性进行全面分析。为了评估这些相关细菌物种之间的遗传交换程度，我们将确定BRD病原体的自然转化系统是否有效，然后测试BRD病原体和相关共生细菌之间的交换效率。将评估细菌利用微生物组成分产生的铁载体或各种宿主铁源来支持铁限制条件下生长的能力。将对这些基因进行敲除，以确认它们在从不同铁源获取铁中的作用。该规划将为制定合理的疫苗战略奠定基础，并确定开发针对所有三种BRD病原体的单一疫苗所需的条件。

My research program involves characterizing iron acquisition systems in important Gram-negative bacterial pathogens of food production animals and developing vaccines for disease prevention. This NSERC application is focused on the pathogens responsible for bovine respiratory disease (BRD) in beef and dairy cattle. The important BRD pathogens (Mannhemia haemolytica, Histophilus somni, Pastuerella multocida) possess surface receptors to extract iron from host transferrin at the bacterial cell surface, providing the ability to proliferate independently from other microbes on the mucosal surface and cause invasive infection. Our vaccine strategy targeting these receptor proteins is based on the premise that we will eliminate the ability of BRD pathogens to proliferate and cause invasive infection but not eliminate related commensal species. However, our current understanding of the prevalence, diversity and exchange of iron acquisition genes amongst the BRD pathogens and related commensal strains is currently inadequate to gauge the reservoir of antigenic variants and the consequence of vaccination on the upper respiratory tract microbiome. Thus the main goals of this program are to determine, (i) the prevalence of iron acquisition genes, (ii) the efficiency of genetic exchange, and (ii) the functional iron acquisition capabilities of pathogenic and commensal strains and species of the Pasteurellacea family that inhabit the bovine upper respiratory tract. We will perform a comprehensive analysis of the presence and diversity of iron acquisition genes present in microbiome samples, in bacteria isolated from microbiome samples and in collections of BRD isolates. In order to evaluate the extent of genetic exchange amongst these related bacterial species we will determine whether the natural transformation systems of the BRD pathogens are functional and then test the efficiency of exchange amongst the BRD pathogens and related commensal bacteria. The ability of the bacteria to use siderophores produced by microbiome constituents or various host iron sources to support growth under iron-limited conditions will be evaluated. Knockouts of the genes will be performed to confirm their role in iron acquisition from different iron sources. This program will provide the foundation for development of rational vaccine strategy and determine what will be required for development of a single vaccine targeting all three BRD pathogens.