Co-evolutionary dynamics between a defensive microbe and a pathogen driven by fluctuating selection

Microbes that protect their hosts from pathogenic infection are widespread components of the microbiota of both plants and animals. It has been found that interactions between ‘defensive’ microbes and pathogens can be genotype-specific and even underlie the variation in host resistance to pathogenic infection. These observations suggest a dynamic co-evolutionary association between pathogens and defensive microbes, but direct evidence of co-evolution is lacking. We tested the hypothesis that defensive microbes and pathogens could co-evolve within host populations by co-passaging a microbe with host-defensive properties (Enterococcus faecalis) and a pathogen (Staphylococcus aureus) within Caenorhabditis elegans nematodes. Using both phenotypic and genomic analyses across evolutionary time, we found patterns of pathogen local adaptation and defensive microbe–pathogen co-evolution via fluctuating selection dynamics. Moreover, co-evolution with defensive microbes resulted in more rapid and ...可保护宿主抵御病原体感染的微生物，是动植物微生物群（microbiota）中广泛分布的组成部分。已有研究表明，‘防御性’微生物与病原体之间的相互作用具有基因型特异性，甚至是宿主对病原体感染抗性产生差异的核心基础。上述观测结果提示，病原体与防御性微生物之间存在动态的协同进化关联，但目前仍缺乏直接的协同进化证据。我们以秀丽隐杆线虫（Caenorhabditis elegans）为实验宿主，将具备宿主防御特性的粪肠球菌（Enterococcus faecalis）与病原体金黄色葡萄球菌（Staphylococcus aureus）进行共传代培养，以此验证“防御性微生物与病原体可在宿主种群内发生协同进化”这一假说。通过跨进化时间尺度的表型与基因组分析，我们观测到了病原体的局部适应模式，以及防御性微生物与病原体通过波动选择动态实现协同进化的现象。此外，与防御性微生物发生协同进化，可使病原体的演化更为迅速且……