What are microorganisms?
Microorganisms are living things that are so small we cannot see them with our eyes. We need a microscope to see them. They live almost everywhere — in air, water, soil and even inside our bodies.
Three main types
- Bacteria — very tiny single living things. Some help make food like yoghurt; some cause illness.
- Fungi — such as yeast and mould. Yeast helps make bread rise.
- Virus — the smallest of all. Many viruses cause diseases such as colds and flu.
Key idea
Microorganisms can be useful (making bread and yoghurt, breaking down waste) or harmful (causing disease and spoiling food).
Useful and harmful
Useful microorganisms help us make food and medicine, and they help rot dead leaves in the soil. Harmful microorganisms can make us sick or spoil our food. We can stop harmful ones by washing hands, cooking food well and keeping food cold.
Remember
- Yeast (a fungus) makes bread rise.
- Bacteria help make yoghurt.
- Viruses cause colds and flu.