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出现和重新出现的传染病的能力至关重要。我的研究计划的目标是利用跨界细菌群泛菌来加深我们对机会性病原体的理解。 Pantoea 是研究机会主义宿主关联演化的理想研究系统。它最初作为植物致病菌群而受到关注，但其成员后来成为皮下和肺部感染以及严重败血症的病原体。然而，目前尚不清楚的是，某些泛菌属物种是否变得越来越专门针对特定宿主，或者是否所有物种都具有引起机会性感染的能力。该提议基于这样的假设：一些泛菌属物种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系统发育学。我们将对代表 12 个不同泛菌属物种的 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以及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描绘物种边界。这种系统发育学将建立进化框架，用于评估毒力是否具有谱系特异性，或者是否独立进化。第二个目标是对蜡虫模型（大蜡螟）中的 96 个测序菌株进行毒力测定，这将评估不同菌株定植宿主并引发感染的能力。蜡虫感染测定将涉及注射细菌接种物，然后评估 48 小时内蜡虫黑化和死亡率。第三个目标是使用比较基因组学来识别候选毒力因子，然后对这些基因进行诱变以评估它们在毒力中的作用。比较基因组学平台 EDGAR 将用于识别最具毒性菌株的常见基因集，这些基因集将代表参与宿主定植的基因。将选择这些基因的子集，并通过在毒性最强的菌株中进行同源重组单独诱变，并在蜡虫中定性和定量地评估所得突变体的毒性。  通过使用我们的系统发育提供的进化框架，我们可以阐明这些毒力能力是谱系特异性的还是独立进化的。 Pantoea 提供了研究机会主义进化的独特机会，这将有助于更好地理解驱动宿主特异性毒力和疾病的进化过程，以及新传染源的出现。