Some fungi form a symbiotic relationship with plant roots, called mycorrhizae. Many kinds of plants require mycorrhizae in order to absorb the nutrients they need for healthy growth. These relationships between fungi and plant roots have developed over millions of years. There are hundreds of different kinds of mycorrhizae, each specially adapted to a certain type of plant. A rich diversity of microbes ensures the right ones are there to get the job done.
Bacteria are single-celled organisms.
Some play in important role in decomposing organic matter, and others produce natural antibiotics that inhibit disease organisms. Many types of beneficial soil bacteria are able to absorb nitrogen from the air and when they die, they make the nitrogen available to plants. Peas and beans are two of the many kinds of plants that require nitrogen-fixing bacteria for healthy growth. Compost is rich with beneficial, disease-suppressing microorganisms that help to keep pathogens under control. Organic matter is what they eat.