The general convention when dealing with biological diversity is to start with the smaller and simpler forms of life--monera, protozoa, then on to the larger and supposedly more complex life forms.  Maybe it is important to avoid lumping biological diverse groups together based only on size. 

But our involvement with the different forms of life does have a tendency to lump them.  Certainly microorganisms are present in the environment.  They are in the water.  They are in the soil.  They are on the bark of trees.  They are on rocks, and sometimes inside of rocks.  They are in other organisms. They are on our toothbrushes.

I am not aware of any special interest groups in Iowa which deal with microorganisms.  However, I recently bought a microscope.  High quality microscopes have become quite inexpensive in recent years, and one can be had for about the price of a video game entertainment device.  They often come with digital cameras as well.  So maybe in the near future you will see the Iowa Microscopy Group, or the Iowa Protozoa Enthusiasts.  Maybe you will see microscopes as standard equipment in libraries, to be shared by all.

The drawing above is from an old book, The Protozoa of Iowa. Charles Howard Edmundson.1906. Davenport Academy of Sciences, Davenport, Iowa. 

This volume is available through the Google digitized books program. I did download it, but unfortunately my copy has some issues with the software so it is not complete. This volume was apparently written as a Doctorial thesis. There are 219 carefully drawn figures, and a quick count yielded 172 species. Some were not identified to species level, and may have even been new species at the time. All of the species were from various waters of the state.

The Illinois Natural Heritage site, referred to in the front page of this biodiversity section suggests that Illinois has more than 112 species of monera, 1406 species of protista (including the non-microscopic slime molds).  Microscopic but multicellular gastrotrichs (60 species) and rotifers (150-175 species) are also present.  Iowa probably has similar but slightly smaller numbers.