The microbes we call germs have been around for a loooong time, and, tiny as they are, they are excellent survivors. You can find traces of microbes in meteorites that have crashed to Earth from other planets and moons, on the tops of the coldest mountains, and bubbling merrily in deep sea volcanic vents. Microbes are survivors. If they "know" anything, it's how to spread and how to live in the most unlikely places.
