During the long history of co-evolution with protists, bacteria have evolved defense strategies to avoid grazing and survive phagocytosis. These mechanisms allow bacteria to exploit phagocytic cells as a protective niche in which to escape from environmental stress and even replicate. Importantly, these anti-grazing mechanisms can function as virulence factors when bacteria infect humans. Here, we discuss how protozoan predation exerts a selective pressure driving bacterial virulence and shaping their genomes, and how bacteria-protist interactions might contribute to the spread of antibiotic resistance as well. We provide examples to demonstrate that besides being voracious bacterial predators, protozoa can serve as melting pots where intracellular organisms exchange genetic information, or even “training grounds” where some pathogens become hypervirulent after passing through. In this special issue, we would like to emphasize the tremendous impact of bacteria-protist interactions on human health and the potential of amoebae as model systems to study biology and evolution of a variety of pathogens. Besides, a better understanding of bacteria-protist relationships will help us expand our current understanding of bacterial virulence and, likely, how pathogens emerge.

在与原生生物共同进化的漫长历史中，细菌已经进化出防御策略来避免放牧和吞噬作用。这些机制允许细菌利用吞噬细胞作为保护生态位，在其中逃避环境压力甚至复制。重要的是，当细菌感染人类时，这些抗放牧机制可以作为毒力因子发挥作用。在这里，我们讨论了原生动物捕食如何施加选择压力来驱动细菌毒力和塑造它们的基因组，以及细菌-原生生物相互作用如何有助于抗生素耐药性的传播。我们提供了一些例子来证明，除了是贪婪的细菌捕食者之外，原生动物还可以作为细胞内生物交换遗传信息的熔炉，甚至是“训练场”，一些病原体在通过后变得超强。在本期特刊中，我们想强调细菌与原生生物相互作用对人类健康的巨大影响，以及阿米巴作为模型系统研究各种病原体生物学和进化的潜力。此外，更好地了解细菌与原生生物的关系将有助于我们扩大目前对细菌毒力以及病原体如何出现的理解。