Real-time host-parasite coevolution in natural microbial communities

所有生态系统的功能最终取决于其细菌群落的多样性。维持这些群落多样性的一个关键因素是病毒，它们在群落内部繁殖并最终杀死细菌。我们最近的工作表明，细菌和它们的病毒在我们周围的土壤中，在几天的时间里不断进化，陷入了共同进化的军备竞赛中，细菌进化出对病毒的抵抗力，病毒进化出克服这种防御的能力。除了影响群落结构外，这种快速的共同进化还具有其他重要的间接影响，例如导致“突变”细菌的进化，从而对其他生物体构成重大的健康风险。我们的目标是跟踪和描述自然环境中细菌和病毒之间的实时共同进化军备竞赛：这是以前从未对任何生物体做过的事情。通过使用独特的遗传标记，我们可以通过时间释放并重新捕获进化的细菌和病毒。我们将利用我们使用下一代测序的经验，将抗性和感染性性状的变化与生物体基因组内发生的突变联系起来。除了描述这些共同进化的动力外，我们还将测试关于环境如何影响共同进化的假设。我们的初步工作表明，根据土壤混合的程度，以及细菌与植物的接近程度，共同进化可能从根本上有所不同，植物为细菌提供了高营养的食物。具体来说，军备竞赛将更加激烈，因此对于在植物周围混合良好的土壤中构建群落具有更大的意义。虽然这项工作调查了土壤中自然细菌-病毒共同进化的相互作用，但其更广泛的含义是广泛的。首先，人们对利用病毒杀死导致人类、动物和农作物感染的细菌越来越感兴趣，因此确定进化在这些生物之间的斗争中的重要性至关重要。其次，对自然环境中实时协同进化的研究在任何其他系统中都是不可能的，这使我们能够测试通过几十年的理论工作、自然调查和实验室研究得出的基本假设。

The functioning of all ecosystems is ultimately dependent on the diversity of its community of bacteria. A key factor maintaining diversity in these communities are viruses that reproduce inside and ultimately kill bacteria. Our recent work has shown that bacteria and their viruses are literally evolving in the soil all around us over a matter of days, locked into coevolutionary arms races where bacteria evolve resistance to viruses and viruses evolve to overcome this defense. As well as affecting community structure, this rapid coevolution has other important indirect effects, such as causing the evolution of 'mutator' bacteria that pose a significant health risk to other organisms. Our aim is to follow and characterise these real-time coevolutionary arms races between bacteria and viruses in natural environments: something never previosuly done for any organisms. By using unique genetic markers, we can release and then re-capture through time the evolving bacteria and viruses. We will take advantage of our experience using next generation sequencing to link changes in resistance and infectivity traits with mutations occurring within the genomes of the organisms.In addition to characterising these coevolutionary dynamics, we will test hypotheses about how the environment affects coevolution. Our preliminary work suggests that coevolution is likely to fundmantally differ based on the extent to which soil is mixed, and how close bacteria are to plants, which exude highly nutritious food for bacteria. Specifically, the arms race will be more intense and hence be of greater significance for structuring communities in well mixed soil around plants.While the work investigates natural bacteria-virus coevolutionary interactions in soil, the broader implications are extensive. First, there is increasing interest in using viruses to kill bacteria that cause infections of humans, animals and crops, hence determing the significance of evolution in the fight between these organisms is crucial. Second, the study of real-time coevolution in natural environments has simply not been possible in any other system, allowing us to test fundamental hypotheses developed through decades of theoretical work, natural surveys and laboratory studies.