The clean-up teams

Decomposers

Compost

Sewage treatment

Nutrient cycles

G The clean-up teams

As living things, all microbes need a source of energy (food). However, this ‘food’ need not be compounds we consider edible. There are microbes that break down oil spills, remove excess nitrogen from polluted water, turn smelly H2S gas into sulfates and make fossil fuels from buried swamps.An oil-contaminated beach can clean itself within a few months through the action of naturally-occurring bacteria which digest hydrocarbons.

The clean-up teams

Decomposers

A decomposer is an organism that breaks down materials, changing them into smaller particles. While earthworms, maggots and slaters are classified as decomposers, most decomposition is done by a wide variety of bacteria and fungi.

These microbes make nutrients such as nitrogen, sulfur, phosphorus and carbon available to other living things.

Saprophytic mushrooms are beginning to break down this tree stump.

Dead leaves are broken down by microbes to make nutrient-rich soil.

The dead wood is broken down by invertebrate and microbial decomposers.

Trees use nutrients from the soil to make wood and leaves.

Compost

When we compost kitchen and garden waste, we speed up the natural process of decomposition. The centre of a compost heap gets hot, and this allows thermophilic (heat loving) microbes to thrive. These microbes are able to break down more complex molecules (such as fat), and the heat they generate kills weed seeds and pathogenic microbes. The finished compost becomes a valuable nutrient source for a new crop of plants.

Sewage treatment

Sewage contains human waste and often contains human pathogens. Sewage treatment plants are needed to prevent these human pathogens from spreading.

A variety of aerobic and anaerobic microbes are used in sewage treatment which digest the compounds contained in the sewage. Human pathogens die because the conditions at the sewage plant are not suitable for their survival.

Nutrient cycles

Ecosystems are very complicated. You may have drawn food chains or food webs to show how energy moves through an ecosystem. Scientists draw nutrient cycles, such as the nitrogen cycle or the carbon cycle, to show how specific elements are recycled within an ecosystem.

The nitrogen cycle shows how nitrogen is recycled in nature.

The clean-up teams

Microbes live in many different conditions and can obtain energy from many different types of compounds.

Most decomposition of dead plant and animal material is done by microbes. This decomposition recycles nutrients such as nitrogen, carbon, sulfur and phosphorus, making these elements available for other living things.

Composting recycles kitchen and garden waste in a heap with a hot centre that kills weed seeds and pathogens.

Sewage treatment uses microbes to break down human waste products.6G 1 A heap of rot 6G 2 Sewage treatment 6G 3 The nitrogen cycle 6G 4 Quiet! Microbes at work

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