Some of the microorganisms include fungi, protozoa, nematodes, and bacteria. They range in size from microscopic to the large mushroom fungi that grow on the surface of the soil or on decaying plant material. They are important for the breaking down of plant materials. Protozoa are microscopic one-celled organisms that live in the moisture of soil. When the soil is dry the protozoa become inactive.
Nematodes are microscopic worms.
They have round bodies that are not segmented. The nematode actually moves by changing the fluid pressure in their bodies. These tiny worms are very abundant. In a typical spade full of moist soil, there may be over a million nematodes. In fact, they are the most abundant multi- celled animals in the soil.