Biofilm is a group of heterogeneously structured and densely packed bacteria with limited access to nutrients and oxygen. These intrinsic features can allow a mono-species biofilm to diversify into polymorphic subpopulations, determining the overall community’s adaptive capability to changing ecological niches. However, the specific biological functions underlying biofilm diversification and fitness adaptation are poorly demonstrated. Here, we launched and monitored the experimental evolution of Pseudomonas aeruginosa biofilms, finding that two divergent molecular trajectories were adopted for adaptation to higher competitive fitness in biofilm formation: one involved hijacking bacteriophage superinfection to aggressively inhibit kin competitors, whereas the other induced a subtle change in c-di-GMP signaling to gain a positional advantage via enhanced early biofilm adhesion. Bioinformatics analyses implicated that similar evolutionary strategies were prevalent among clinical P. aeruginosa strains, indicative of parallelism between natural and experimental evolution. Divergence in the molecular bases illustrated the adaptive values of genomic plasticity for gaining competitive fitness in biofilm formation. Finally, we demonstrated that these fitness-adaptive mutations reduced bacterial virulence. Our findings revealed how the mutations intrinsically generated from the biofilm environment influence the evolution of P. aeruginosa.

中文翻译：

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不同的分子策略驱动生物膜形成中竞争适应性的进化适应


生物膜是一组结构异质且密集的细菌，其获取营养和氧气的机会有限。这些内在特征可以使单一物种生物膜多样化为多态亚群，从而决定整个群落对不断变化的生态位的适应能力。然而，生物膜多样化和适应适应的具体生物学功能却很少得到证实。在这里，我们启动并监测了铜绿假单胞菌生物膜的实验进化，发现采用了两种不同的分子轨迹来适应生物膜形成中更高的竞争适应性：一种涉及劫持噬菌体重复感染以积极抑制亲缘竞争者，而另一种则诱导微妙的变化参与 c-di-GMP 信号传导，通过增强早期生物膜粘附来获得位置优势。生物信息学分析表明，临床铜绿假单胞菌菌株中普遍存在类似的进化策略，表明自然进化和实验进化之间存在平行性。分子基础的差异说明了基因组可塑性对于在生物膜形成中获得竞争适应性的适应性价值。最后，我们证明这些适应性突变降低了细菌毒力。我们的研究结果揭示了生物膜环境本质上产生的突变如何影响铜绿假单胞菌的进化。