Uncovering the genetic basis for host-specific adaptation and opportunism in the bacterial pathogen, Pantoea

揭示细菌病原体泛菌属宿主特异性适应和机会主义的遗传基础

• 批准号: RGPIN-2021-02863
• 负责人: Stavrinides, John
• 金额: $ 2.62万
• 依托单位: University of Regina
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=745899
• 关键词: Uncovering; genetic; basis; host; specific

Understanding the host range and virulence potential of bacterial pathogens is central to our ability to predict and control emerging and reemerging infectious diseases. The objective of my research program is to advance our understanding of opportunistic pathogens using the cross-kingdom bacterial group, Pantoea. Pantoea serves as the ideal study system for examining the evolution of opportunistic host association. It initially gained attention as a plant pathogenic group, but its members have since emerged as the causal agents of subcutaneous and pulmonary infections, and severe septicemia. What is unclear, however, is whether some Pantoea species have become increasingly more specialized to specific hosts, or whether all have the capacity for causing opportunistic infections. This proposal rests on the hypothesis that there are genetic determinants in some Pantoea species that facilitate host colonization and virulence. The first aim is to use whole genome data to establish a fully resolved Pantoea phylogeny. We will sequence 96 new genomes representing 12 different species of Pantoea, including pathogens of insects, plants, and humans, as well as environmental strains. We will use whole genome information together with average nucleotide identity and genetic distance of core genes to create a phylogenetic tree and delineate species boundaries. This phylogeny will establish the evolutionary framework for evaluating whether virulence is lineage specific, or whether it evolved independently. The second aim is to carry out virulence assays of the 96 sequenced strains in the waxworm model, Galleria mellonella, which will evaluate the ability of different strains to colonize the host and initiate infection. Infection assays with waxworms will involve injection with bacterial inoculum, followed by an assessment of waxworm melanization and mortality over a 48 hour period. The third objective will be to identify candidate virulence factors using comparative genomics, and then mutagenize these genes to assess their role in virulence. The comparative genomics platform, EDGAR, will be used to identify common gene sets across the most virulent strains, which will represent genes involved in host colonization. A subset of these genes will be selected and mutagenized individually by homologous recombination in the most virulent strains, and the virulence of the resulting mutants evaluated in the waxworm both qualitatively and quantitatively.  By using the evolutionary framework provided by our phylogeny, we can elucidate whether these virulence capabilities are lineage-specific or if they evolved independently. Pantoea provides a unique opportunity to study the evolution of opportunism, which will lead to a better understanding of the evolutionary processes that drive host-specific virulence and disease, and the emergence of new infectious agents.

了解细菌病原体的宿主范围和毒力潜力对于我们预测和控制新发和再发传染病的能力至关重要。我的研究计划的目标是提高我们的机会病原体的理解，使用跨王国的细菌群，泛菌。泛菌作为理想的研究系统，研究机会宿主协会的演变。它最初作为一个植物致病菌群而受到关注，但其成员已成为皮下和肺部感染以及严重败血症的致病因子。然而，目前尚不清楚的是，一些泛菌属物种是否已经变得越来越专门针对特定宿主，或者是否所有物种都有能力引起机会性感染。这一建议基于这样的假设，即在某些泛菌属物种中存在促进宿主定殖和毒力的遗传决定因素。 第一个目标是利用全基因组数据建立完全解析的泛菌遗传学。我们将对代表12种不同泛菌属物种的96个新基因组进行测序，包括昆虫、植物和人类的病原体，以及环境菌株。我们将使用全基因组信息，结合核心基因的平均核苷酸同一性和遗传距离来创建系统发育树并划定物种边界。这一系统发生学将建立进化框架，以评估毒力是谱系特异性的，还是独立进化的。第二个目标是在蜡虫模型大蜡螟中对96个测序菌株进行毒力测定，这将评估不同菌株定殖宿主和启动感染的能力。用蜡虫进行的感染测定将涉及注射细菌接种物，然后评估48小时内的蜡虫黑化和死亡率。第三个目标是利用比较基因组学鉴定候选毒力因子，然后诱变这些基因以评估它们在毒力中的作用。比较基因组学平台埃德加将用于确定最强毒株的共同基因组，这些基因组将代表参与宿主定植的基因。这些基因的一个子集将被选择和诱变个别同源重组在最毒力菌株，和由此产生的突变体的毒力评价在蜡虫定性和quantitatives.By使用我们的进化提供的框架，我们可以阐明这些毒力能力是否是谱系特异性的，或者如果他们独立进化。泛菌提供了一个独特的机会来研究机会主义的演变，这将导致更好地了解进化过程，驱动主机特定的毒力和疾病，以及新的传染性病原体的出现。