Spatial patterns of coevolution in multispecies host-parasite interactions

疟疾和猪流感等传染病继续对人类健康造成重大问题，而口蹄疫等病毒性疾病和叶枯病等细菌性病原体则对我们的食物供应构成重大威胁。同样，传染病在自然界广泛存在，对我们的环境构成严重威胁。由于这些疾病对它们的植物或动物宿主造成重大伤害，它们像所有其他生物体一样，随着时间的推移而进化。细菌病原体对抗生素产生耐药性的能力日益引起人们的关注，并促使人们继续寻找控制疾病传播的替代方法。一个有希望的替代方案是使用噬菌体（感染并打开细菌细胞的病毒）来控制细菌种群的生长。“噬菌体疗法”，即使用噬菌体病毒的组合来靶向和感染特定的致病性细菌菌株，正开始成为一种安全和商业上可行的管理策略。当然，细菌宿主也可以进化以保护自己免受寄生虫的侵害，例如噬菌体，因此研究噬菌体与其细菌宿主之间的“共同进化”是至关重要的。我的提案将研究一些关键问题，以了解宿主-寄生虫共同进化的核心。首先，我将确定噬菌体是否与细菌病原体，番茄植物叶片中的丁香假单胞菌（细菌是重要的农业病原体）和七叶树木质部或韧皮部中的细菌（细菌引起出血溃疡病并威胁自然种群）共同进化。我正在使用这两个系统，以便我可以将自然界中细菌和噬菌体之间的相互作用与受控的实验室实验结果进行比较，从而使我能够直接研究共同进化的过程和含义。我将研究植物环境如何影响细菌和噬菌体之间的共同进化，以及噬菌体感染如何影响细菌对其植物宿主造成的损害程度。这项工作对于评估噬菌体治疗作为控制细菌性疾病的机制的长期意义至关重要。此外，这项研究将强调共同进化往往比简单的两个物种的相互作用更复杂，而且理解多物种的相互作用是预测疾病在自然界中如何进化的关键。

Infectious diseases such as Malaria and Swine Flu continue to cause major problems to human health while viral diseases, such as Foot and Mouth, and bacterial pathogens, like Leaf Blight, are a major threat to our food supply. Similarly, infectious diseases are widespread in nature and pose a severe threat to our environment. Since these diseases cause significant harm to their plant or animal hosts they, like all other organisms, evolve through time. The ability of bacterial pathogens to evolve resistance to antibiotics is of increasing concern and has fuelled a continued search for alternative ways to control the spread of disease. One promising alternative is the use of bacteriophages (viruses that infect and burst open bacterial cells) to control the growth of bacterial populations. 'Phage therapy', in which combinations of bacteriophage viruses are used to target and infect specific pathogenic strains of bacteria, is beginning to emerge as a safe and commercially viable management strategy. Of course, bacterial hosts can also evolve to defend themselves against parasites, such as phage, and it is thus crucial to study the 'coevolution' between phage and their bacterial hosts. My proposal will examine a number of key issues central to understanding host-parasite coevolution. First, I will determine whether phage are coevolving with the bacterial pathogen, Pseudomonas syringae within leaves of tomato plants (where the bacteria is an important agricultural pathogen) and within the xylem or phloem of horse chestnut trees (where the bacteria is causing bleeding canker disease and threatening natural populations). I am using these two systems so that I can compare the interaction between bacteria and phage in nature with results from controlled, laboratory experiments, allowing me to directly investigate the process and implications of coevolution. I will examine both how the plant environment influences the coevolution between bacteria and phage and how infection by phage influences the amount of damage that the bacteria cause to their plant host. This work will be critical to evaluating the long-term implications of phage therapy as a mechanism for controlling bacterial disease. Further, this research will emphasise that coevolution is often more complex than simple, two species interactions and that understanding multi-species interactions is key to making predictions of how diseases will evolve in nature.