Rotifers - Microscopic animals that thrive in moist swampy conditions. Their activities are confined largely to peat bogs and very wet areas. The plant roots exude sugars to feed the fungi and the fungi carry in soil nutrients which might otherwise by deficient in the plant. Hundreds of mycorrhizal species associate only with trees. The roots of most agronomic crops including corn, cotton, wheat, potatoes, beans, alfalfa, sugarcane, cassava, and dryland rice have mycorrhizal associations.
Actinomycetes are filamentous like molds, but mycelial threads are smaller and profusely branched.
Bacteria single cell organisms like moist soil conditions, do best at moisture conditions optimum for higher plants. Sources of Carbon and Energy Heterotrophic - obtain their energy and carbon from the breakdown of organic materials. Autotrophic - obtain their energy and carbon from other sources, such as energy from the sun and carbon from CO 2 . Photoautotrophs - use solar energy. However, nitrogen is the element most limiting to plant growth.