Microorganisms are essential to soil formation and soil ecology because they control the flux of nutrients to plants (i.e., control of carbon, nitrogen, and sulfur cycles,), promote nitrogen fixation, and promote soil detoxification of inorganic and naturally occurring organic pollutants. Soil microorganisms are also part of several food chains, thus serving as source nutrients to one another, and frequently serve as the primary members of food chains in soil biota.

The roots of plants are also part of soil biota and some fungi. Many bacteria live in symbiotic relation to plant roots, around which there is an area of elevated microbial activity, known as rhizosphere. The Animalia kingdom is also represented in soil biota by Nematodes, Earthworms, Mollusks, Acarina, Collembola, as well as several insects and larvae that feed mostly on decaying organic matter. They all take part in...