Mold

Have you ever observed how an organic matter decays in a dry environment versus wet? 

For example, grass in too much sun may dry up.  However, if you were to grow grass in a moist closed environment, it will develop mold.

Now compare this to our stomach environment.  

How much people do to create a perfect bacteria, and how many "probiotics" of all sorts they take!

In a swampy soil there will exist its own organisms, naturally.  Compare that to a running stream.

Think about all this.