Microorganisms · Year 9
Microorganisms (microbes) are living things too small to see without a microscope. The main groups are bacteria, viruses and fungi. Some are useful, some cause disease, and we can stop harmful ones from spreading.
Key facts
- Bacteria are single cells with no nucleus (the microbes in yoghurt, Salmonella). Viruses are much smaller particles that can only reproduce inside living cells (colds, flu, measles). Fungi include yeasts, moulds and mushrooms.
- A virus is much smaller than a bacterium, and a bacterium is smaller than a yeast cell.
- Useful microbes: yeast makes bread rise and is used to make beer and wine; bacteria make yoghurt and cheese; the mould Penicillium makes penicillin; decomposers recycle nutrients.
- Harmful microbes (pathogens) cause disease and make food go off. They spread through the air, water, food, touch and animals such as mosquitoes.
- Microbes grow fastest where it is warm and damp, with food. A fridge slows them down; cooking kills them.
- To stop the spread: wash your hands, catch coughs and sneezes in a tissue, cook food thoroughly, keep food cool, drink clean water and be vaccinated.
- Antibiotics kill bacteria but not viruses.