1. Bacteria: Examples include Rhizobium, Nitrosomonas, and Bacillus. 2. Fungi: Examples include Mycorrhizae, Penicillium, and Trichoderma. 3. Protozoa: Examples include Amoeba, Paramecium, and Euglena. 4. Algae: Examples include Chlorella, Spirogyra, and Diatoms. 5. Actinomycetes: Examples include Streptomyces and Actinomyces. 6. Nematodes: Examples include C. elegans and root-knot nematodes.