Decomposers break down dead or decaying organisms, and in doing so, convert their basic materials into forms more useful to the biological community, particularly plants. The main decomposers in the environment include bacteria, fungi and worms. Each of these plays a different, but overlapping, role in decomposition.
Bacteria are ubiquitous and act as decomposers for all types of biological material. They are vital to the recycling of nutrients and are the key decomposers in many nutrient cycles. Fungi break down many materials as well, but are particularly important in forest ecosystems. They are some of the only organisms that can easily break down wood completely. They grow as multiple strands of cells that can break through the surface of objects such as logs to digest their interiors, and they have enzymes to break down parts of trees that other organisms cannot.
Earthworms are animal decomposers that ingest dead plant and animal matter along with soil and excrete wastes in a much more useful form. In addition to making nutrients more accessible to plants, earthworms also aerate and mix soil by burrowing through it, which is important for the growth of plants. Many animals that are scavengers of dead organisms can also be considered decomposers.