How do decomposer microorganisms recycle nutrients in ecosystems?

Decomposer microorganisms, such as bacteria and fungi, recycle nutrients in ecosystems through a process called decomposition. By breaking down complex organic matter—such as dead plants and animals—into simpler chemical compounds, they return essential elements to the environment in forms that living plants can absorb and reuse.123

This recycling process typically follows these stages:

• Biofragmentation: Saprotrophic organisms excrete enzymes that break down complex polymers into smaller molecules, such as monomers and dimers. For example, fungi use specialized enzymes to digest cellulose, a complex carbohydrate found in plant cell walls that most other organisms cannot metabolize.43
• Assimilation: The microorganisms absorb these fragmented compounds into their cells to obtain energy and nutrients for their own growth and reproduction.4
• Mineralization: This final stage converts organic matter into inorganic substances like water, carbon dioxide, and various mineral ions (such as nitrates and ammonium).4

These activities are vital to natural cycles, including the carbon cycle, nitrogen cycle, and sulfur cycle, ensuring that nutrients remain available to sustain life within the ecosystem.12