Biotype-specific evolution

项目摘要 霍乱目前是由O 1血清群El Tor生物型霍乱弧菌引起的，它出现于1961年，引发了霍乱流行。 第七次大流行。前6次霍乱大流行是由O 1血清群经典生物型V引起的。 胆汁。在过去的60年里，经典生物型基本上已经从水生环境中消失 也是霍乱的原因之一然而，其原因尚不清楚。环境中的霍乱弧菌 与许多脊椎鱼类有关。拟议的工作将使用斑马鱼模型为V。 霍乱弧菌，可以调查霍乱弧菌和天然水生宿主之间的相互作用，覆盖整个 传染周期先前的工作发现，在斑马鱼定居的时间轴上，经典的 和El Tor生物型，经典型在72小时内被清除，El Tor能够定殖长达14天， 高水平的细菌复制。我们假设，这种长期的鱼类定居和复制提供了 El Tor具有强大的选择优势，使其能够在环境利基中取代经典。霍乱弧菌 Tor生物型有两个致病岛，称为VSP-1和VSP-2，这是经典型所缺乏的。初步数据 实验表明缺失VSP-1的El Tor菌株具有正常的鱼定殖表型，而缺失VSP-1的El Tor菌株具有正常的鱼定殖表型。 缺失VSP-2的菌株在长期定殖方面有缺陷。因此，很可能VSP-2中的基因 对长期殖民至关重要本提案的目标1将使用逐步删除策略， 和表征VSP-2内对延长定殖重要的基因，并评估这种基因是否 基因足以延长经典的殖民。在宿主方面，先天免疫和适应性免疫提供了 保护免受入侵的病原体。鱼类具有与哺乳动物非常相似的先天免疫反应， 适应性免疫反应，在生命的前4-6周内发展。我们假设经典生物型 通过严格的先天反应迅速清除，而El Tor只能通过适应性免疫清除。 反应本提案的目标2-1将使用具有完全功能的斑马鱼幼鱼来测试这些假设。 先天反应，但未开发的适应性反应。目标2-2将进一步检验El Tor 清除需要通过使用在适应性免疫中有缺陷的斑马鱼突变体的适应性免疫。 完成拟议的工作，使用斑马鱼作为环境V.霍乱宿主模型，将显着 推进我们对天然储层中V. cholesterol演化和选择性压力的理解。长期 这项工作的目标是更好地了解霍乱弧菌的生命周期，它如何有助于人类的发病机制， 并确定新的战略，以打击霍乱弧菌疾病和传播。 .

PROJECT SUMMARY Cholera is presently caused by O1 serogroup, El Tor biotype V. cholerae, which emerged in 1961 to initiate the ongoing seventh pandemic. The prior 6 cholera pandemics were caused by O1 serogroup classical biotype V. cholerae. Over the past 60 years, classical biotype has essentially disappeared from the aquatic environment and as a cause of cholera. However, the reasons for this are unknown. V. cholerae in the environment is found in association with numerous vertebrate fish species. The proposed work will use a zebrafish model for V. cholerae that can investigate interactions between V. cholerae and natural aquatic hosts covering the entire infectious cycle. Previous work found dramatic differences in the timeline of zebrafish colonization by classical and El Tor biotypes, with classical being cleared within 72 h and El Tor able to colonize for up to 14 days with high levels of bacterial replication. We hypothesize that this prolonged fish colonization and replication provided a strong selective advantage to El Tor, allowing it to replace classical in environmental niches. V. cholerae El Tor biotype has 2 pathogenicity islands termed VSP-1 and VSP-2 that classical lacks. Data from preliminary experiments indicate an El Tor strain deleted for VSP-1 has a normal fish colonization phenotype, whereas a strain deleted for VSP-2 is defective in prolonged colonization. Therefore, it is likely that gene(s) within VSP-2 are essential for prolonged colonization. Aim 1 of this proposal will use a progressive deletion strategy to identify and characterize gene(s) within VSP-2 that are important for prolonged colonization and assess whether such genes are sufficient to prolong classical colonization. On the host side, innate and adaptive immunity provide protection from invading pathogens. Fish have innate immune responses very similar to mammals, as well as adaptive immune responses that develop over the first 4-6 weeks of life. We hypothesize that classical biotype is rapidly cleared by a strictly innate response, whereas El Tor can only be cleared by an adaptive immune response. Aim 2-1 of this proposal will test these hypotheses using larval zebrafish, which have a fully functioning innate response but an undeveloped adaptive response. Aim 2-2 will further test the hypothesis that El Tor clearance requires adaptive immunity by using zebrafish mutants that are defective in adaptive immunity. Completion of the proposed work, using zebrafish as an environmental V. cholerae host model, will significantly advance our understanding of V. cholerae evolution and selective pressures in a natural reservoir. The long term goal of this work is to better understand the V. cholerae life cycle, how it contributes to pathogenesis in humans, and identify new strategies to combat V. cholerae disease and transmission. .