It is undisputed that microorganisms can adapt to changes in their environment. One of the types of changes microbial communities are currently exposed to is the release of large quantities and varieties of organic and inorganic substances into the environment. These substances can act as the "triggers" for different kinds of adaptation of microbial communities. Thus, various evolutionary mechanisms at work in adapting bacterial populations can be observed. From an environmental viewpoint, adaptation of microbial communities is beneficial when microorganisms that can completely degrade polluting substances evolve (e.g., natural attenuation).