PDF(Pubmed)
Abstract：
Bacterial interactions with surfaces rely on the coordinated expression of a vast repertoire of surface-exposed adhesins. However, how bacteria dynamically modulate their adhesion potential to achieve successful surface colonization is not yet well understood. Here, we investigated changes in adhesion capacity of an initially poorly adherent Escherichia coli strain using experimental evolution and positive selection for mutations improving adhesion and biofilm formation on abiotic surfaces. We showed that all identified evolved populations and clones acquired mutations located almost exclusively in the lectin domain of fimH, the gene coding for the α-d-mannose-specific tip adhesin of type 1 fimbriae, a key E. coli virulence factor. While most of these fimH mutants showed reduced mannose-binding ability, they all displayed enhanced binding to abiotic surfaces, indicating a trade-off between FimH-mediated specific and nonspecific adhesion properties. Several of the identified mutations were already reported in the FimH lectin domain of pathogenic and environmental E. coli, suggesting that, beyond pathoadaptation, FimH microevolution favoring nonspecific surface adhesion could constitute a selective advantage for natural E. coli isolates. Consistently, although E. coli deleted for the fim operon still evolves an increased adhesion capacity, mutants selected in the ∆fim background are outcompeted by fimH mutants revealing clonal interference for adhesion. Our study therefore provides insights into the plasticity of E. coli adhesion potential and shows that evolution of type 1 fimbriae is a major driver of the adaptation of natural E. coli to colonization.
摘要：
细菌与表面的相互作用依赖于大量表面暴露的粘附素的协调表达。然而,细菌如何动态调节其粘附潜力以实现成功的表面定植尚不清楚。这里,我们使用实验进化和阳性选择来研究最初粘附性差的大肠杆菌菌株的粘附能力变化，以改善非生物表面上的粘附和生物膜形成。我们表明，所有确定的进化种群和克隆都获得了几乎完全位于fimH的凝集素域的突变，编码1型菌毛的α-d-甘露糖特异性尖端粘附素的基因，一个关键的大肠杆菌毒力因子.虽然大多数这些fimH突变体显示出降低的甘露糖结合能力，它们都显示出对非生物表面的增强结合，表明FimH介导的特异性和非特异性粘附特性之间的权衡。已在致病性和环境大肠杆菌的FimH凝集素结构域中报道了几种已鉴定的突变，这表明，超越病态适应，有利于非特异性表面粘附的FimH微进化可以构成天然大肠杆菌分离株的选择性优势。始终如一，尽管对于fim操纵子缺失的大肠杆菌仍然进化出增加的粘附能力，fimH突变体揭示了对粘附的克隆干扰。因此，我们的研究提供了对大肠杆菌粘附潜力的可塑性的见解，并表明1型菌毛的进化是天然大肠杆菌适应定植的主要驱动因素。
