List of functional groups of microorganisms?

I just started reading a beginners book on building soil. In it the author makes a reference to 30 or so functional groups of microorganisms needed for healthy soil and proceeds to list 3 (decomposing, nitrogen cycling and photosynthesizing). Is there a more comprehensive list of these (30 or so) functional groups where I can do some more research? Thanks

These sites should get you on your way; soil and plant laboratory bioworks extension org Happy researching, you will love this subject if you are of the scientific mind set. Don't forget Mycorrhizae all plants seem to benefit from these fungi helpers.