Inspired by the news/discovery that microbes in space (such as on the ISS) are evolving and adapting for life in space. They are now much better-suited to those environments, can stay alive there, etcetera.
This will always happen, because microbes duplicate much faster and are much smaller/more reproductive.
Which leads to the following story idea: What if this happens on a spaceship, with the astronauts being outpaced by the germs/microbes/smaller creatures they brought with them, and now they’re basically fighting against the other species they deemed lesser?