Predation by heterotrophic protists drives the emergence of adaptive traits in bacteria, and often these traits lead to altered interactions with hosts and persistence in the environment. Here we studied adaptation of the cholera pathogen, Vibrio cholerae during long-term co-incubation with the protist host, Acanthamoeba castellanii. We determined phenotypic and genotypic changes associated with long-term intra-amoebal host adaptation and how this impacts pathogen survival and fitness. We showed that adaptation to the amoeba host leads to temporal changes in multiple phenotypic traits in V. cholerae that facilitate increased survival and competitive fitness in amoeba. Genome sequencing and mutational analysis revealed that these altered lifestyles were linked to non-synonymous mutations in conserved regions of the flagellar transcriptional regulator, flrA. Additionally, the mutations resulted in enhanced colonisation in zebrafish, establishing a link between adaptation of V. cholerae to amoeba predation and enhanced environmental persistence. Our results show that pressure imposed by amoeba on V. cholerae selects for flrA mutations that serves as a key driver for adaptation. Importantly, this study provides evidence that adaptive traits that evolve in pathogens in response to environmental predatory pressure impact the colonisation of eukaryotic organisms by these pathogens.

异养原生生物的捕食推动了细菌适应性特征的出现，而且这些特征通常会导致与宿主的相互作用发生改变并在环境中持久存在。在这里，我们研究了霍乱病原体霍乱弧菌在与原生生物宿主Acanthamoeba castellanii长期共孵育期间的适应情况。我们确定了与变形虫内宿主长期适应相关的表型和基因型变化，以及这如何影响病原体的生存和适应性。我们表明，对变形虫宿主的适应会导致霍乱弧菌多种表型性状的时间变化这有助于提高变形虫的生存能力和竞争力。基因组测序和突变分析表明，这些改变的生活方式与鞭毛转录调节因子flrA保守区域的非同义突变有关。此外，突变导致斑马鱼的定植增强，建立了霍乱弧菌适应变形虫捕食和增强环境持久性之间的联系。我们的结果表明变形虫对霍乱弧菌施加的压力选择flrA作为适应的关键驱动因素的突变。重要的是，这项研究提供的证据表明，病原体响应环境捕食压力而进化的适应性特征会影响这些病原体对真核生物的定植。