In natural environments, bacteria do not usually live as dispersed single cells but as biofilms, which are aggregates of bacteria in a self-produced matrix of extracellular polymeric substances. Biofilms are often attached to surfaces or form at air-liquid interfaces and mutants with increased biofilm formation are common in clinical and environmental isolates. These mutants are particularly problematic as a cause of chronic infections as they are less susceptible to antibiotics and have increased immune evasion. Mutants with similar biofilm phenotypes caused by similar mutations as those found in clinical isolates can be isolated after experimental evolution in simple laboratory environments and can be utilized as a unique model system for testing and developing our ability to predict evolution.

Source: Pentz  JT, Lind PA(2021)Evolutionary forecasting of phenotypic and genetic outcomes of experimental evolution in Pseudomonas protegens Pf-5. PLoS Genetics 17(8): e1009722.