While protozoa are many times larger than bacteria, you still need a microscope to see them. A pinch of soil can contain thousands. Protozoa are classified into three groups based on structural peculiarities. Ciliates are the biggest and use many hair-like cilia to scoot through soil and water.
Flagellates are the smallest and swim using a few whip-like flagella.
All protozoa need water to move through soil, however, they only need a thin film surrounding the soil particles to get around. Believe it or not, they can be quite active even in very parched desert soils. Why They Are Important Protozoa play an important role in the structure of the soil food web. Protozoa eat bacteria and release nitrogen and other nutrients in their waste. Since protozoa are concentrated near plant roots, the plant can benefit from this supply of nutrients.