Decomposers and Decay

Decay is an essential life process, which helps to digest food and recycle materials. Bacteria and fungi are the main groups of decomposer. They release enzymes to break down compounds, so that they can absorb the nutrients. We can preserve our food, for example by freezing or canning, to remove the conditions needed for decay to occur.

Decay is essential to our survival – it helps to digest food, and to recycle materials in our environment. Sometimes it can cause problems too, such as food spoilage (food going off).

The main groups of decomposer organisms are bacteria and fungi. Bacteria are single-celled microscopic organisms. Fungi are often larger organisms that include moulds and mushrooms. They both cause decay by releasing enzymes which break down compounds in their food so it can be absorbed by their cells. Organisms that feed on dead material in this way are called saprophytes.

What factors affect decay?

• Temperature - High temperatures prevent decay, low temperatures slow decay. High temperatures destroy enzymes and proteins, killing the organisms responsible for decay. Low temperatures slow the rate of reaction of enzymes and will prevent growth and reproduction.
• Oxygen - Lack of oxygen will slow or prevent most forms of decay Oxygen is needed for respiration by organisms. Some bacteria can survive without oxygen, such as those used in biogas generators.
• Water - Lack of water will slow or prevent decay Water is needed for transport and to support reactions inside organisms. Decay organisms need water to digest their food.

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Speeding up Decomposers

Decomposers such as bacteria and fungi cause decay at microscopic level. Other larger organisms help speed up decay by feeding on dead matter and breaking it down into smaller pieces, so increasing the surface area for the bacteria and fungi.

These larger organisms include earthworms that help break down dead leaves, woodlice that break down wood and maggots that feed on animal tissue. These larger organisms are detritivores