In places where there is a scarcity of space, microbes will not reproduce. In reproducing they would actually be destroying themselves because of the lack of space and possible nutrients. Nutrients are essential to life. If the microbes are to survive they must have these nutrients. Microbes, like all life forms, adapt to their environment so that they may survive.
Temperature is another factor that microbes and all life forms adapt to.
We humans have a certain temperature range that we can exist in. The microbes have their temperature range. Again, adaptation to the environment is the important factor here. I think that is what this article is all about, on how the discovery of this subsurface microbes have adapted to living in their harsh environments. This article is about using cloning technology for medical purposes.