Identifying genetic factors that contribute to the evolution of adaptive phenotypes in pathogenic bacteria is key to understanding the establishment of infectious diseases. In this study, we performed mutation accumulation experiments to record the frequency of mutations and their effect on fitness in hypermutator strains of the environmental bacterium Pseudomonas aeruginosa in comparison to the host-niche-adapted Salmonella enterica. We demonstrate that P. aeruginosa, but not S. enterica, hypermutators evolve toward higher fitness under planktonic conditions. Adaptation to increased growth performance was accompanied by a reversible perturbing of the local genetic context of membrane and cell wall biosynthesis genes. Furthermore, we observed a fine-tuning of complex regulatory circuits involving multiple di-guanylate modulating enzymes that regulate the transition between fast growing planktonic and sessile biofilm-associated lifestyles. The redundancy and local specificity of the di-guanylate signaling pathways seem to allow a convergent shift toward increased growth performance across niche-adapted clonal P. aeruginosa lineages, which is accompanied by a pronounced heterogeneity of their motility, virulence, and biofilm phenotypes.

确定有助于病原菌适应性表型进化的遗传因素是了解传染病形成的关键。在这项研究中，我们进行了突变积累实验，以记录突变频率及其对环境细菌铜绿假单胞菌超突变菌株与适应宿主生态位的肠道沙门氏菌适应性的影响。我们证明P. aeruginosa，但不是S. enterica，超突变体在浮游条件下向更高的适应性进化。适应增加的生长性能伴随着膜和细胞壁生物合成基因的局部遗传背景的可逆扰动。此外，我们观察到涉及多种二鸟苷酸调节酶的复杂调节回路的微调，这些调节酶调节快速生长的浮游生物和固定生物膜相关生活方式之间的转变。双鸟苷酸信号通路的冗余性和局部特异性似乎允许向适应小生境的克隆铜绿假单胞菌谱系的生长性能的提高趋同转变，这伴随着它们的运动性、毒力和生物膜表型的明显异质性。