Institut Pasteur, Université de Paris Cité, CNRS, UMR3525, Microbial Evolutionary Genomics, F-75015, Paris, France.
NPJ Biofilms Microbiomes. 2023 Aug 3;9(1):53. doi: 10.1038/s41522-023-00422-3.
Adaptation to one environment can often generate phenotypic and genotypic changes which impact the future ability of an organism to thrive in other environmental conditions. In the context of host-microbe interactions, biofilm formation can increase survival rates in vivo upon exposure to stresses, like the host's immune system or antibiotic therapy. However, how the generic process of adaptation impacts the ability to form biofilm and how it may change through time has seldomly been studied. To do so, we used a previous evolution experiment with three strains of the Klebsiella pneumoniae species complex, in which we specifically did not select for biofilm formation. We observed that changes in the ability to form biofilm happened very fast at first and afterwards reverted to ancestral levels in many populations. Biofilm changes were associated to changes in population yield and surface polysaccharide production. Genotypically, mutations in the tip adhesin of type III fimbriae (mrkD) or the fim switch of type I fimbriae were shaped by nutrient availability during evolution, and their impact on biofilm formation was dependent on capsule production. Analyses of natural isolates revealed similar mutations in mrkD, suggesting that such mutations also play an important role in adaptation outside the laboratory. Our work reveals that the latent evolution of biofilm formation, and its temporal dynamics, depend on nutrient availability, the genetic background and other intertwined phenotypic and genotypic changes. Ultimately, it suggests that small differences in the environment can alter an organism's fate in more complex niches like the host.
适应一种环境通常会产生表型和基因型的变化，从而影响生物体在其他环境条件下茁壮成长的未来能力。在宿主-微生物相互作用的背景下，生物膜的形成可以增加生物体在暴露于压力（如宿主免疫系统或抗生素治疗）时的存活率。然而，适应的一般过程如何影响生物膜形成的能力，以及它如何随时间变化，很少被研究。为此，我们使用了以前的一个进化实验，涉及三种肺炎克雷伯菌种复合体菌株，在该实验中，我们特别没有选择生物膜形成。我们观察到，生物膜形成能力的变化起初非常迅速，随后在许多种群中恢复到祖先水平。生物膜的变化与种群产量和表面多糖产生的变化有关。从基因型上看，III 型菌毛尖端黏附素（mrkD）或 I 型菌毛的 fim 开关的突变是由进化过程中的营养可用性决定的，它们对生物膜形成的影响取决于荚膜的产生。对自然分离株的分析显示 mrkD 中存在类似的突变，表明这些突变在实验室外的适应中也起着重要作用。我们的工作揭示了生物膜形成的潜在进化及其时间动态取决于营养可用性、遗传背景和其他相互交织的表型和基因型变化。最终，这表明环境中的微小差异可以改变生物体在宿主等更复杂生态位中的命运。
