Microbes are faced with environmental fluctuations and it is therefore important to understand how change affects bacterial evolution and population dynamics. Here, we evolved a model bacterium, Pseudomonas aeruginosa PA14, under both constant and changing conditions where settlement by biofilm formation or migration by swimming motility was induced. In changing environments, a heterogeneous population evolved with both specialists and generalists. Interestingly, over time, generalists were outcompeted despite being better at both phenotypes compared to the ancestor. However, generalists became dominant when faced with local competition after resettlement. Reintroduction into a burn wound model, the environment PA14 originally was isolated from, further suggested a tradeoff between niche breadth and peak fitness in agreement with the evolution experiments. Mutations in the c-di-GMP system were key for adaptation of the phenotypes. No mutants lost their ability to regulate c-di-GMP, but generalists acquired mutations that optimized their phenotypic response by efficiently adjusting c-di-GMP levels.

中文翻译：

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环境变化过程中表型转换的适应性进化

微生物面临环境波动，因此了解变化如何影响细菌进化和种群动态非常重要。在这里，我们进化出一种模型细菌，铜绿假单胞菌在不断变化的条件下，PA14会诱导生物膜形成沉降或游泳运动引起迁移。在不断变化的环境中，异类种群由专家和通才演变而成。有趣的是，随着时间的流逝，通才尽管在两种表型上都比祖先更好，但他们的竞争却不那么成功。但是，在重新安置后面对当地竞争时，通才才是主导。重新引入烧伤创面模型时，原本是从PA14环境中分离出来的，进一步证明了生态位宽度和峰适应性之间的权衡与进化实验一致。c-di-GMP系统中的突变是适应表型的关键。没有突变体失去调节c-di-GMP的能力，