Introduction to Microbes

What is a microbe? Some living things are so small that we can only see them with a microscope These are called micro-organisms or microbes They include: Bacteria Viruses Fungi

Bacteria Found everywhere – in the air, in the soil, in water, inside living things Some are useful but some cause diseases such as pneumonia, scarlet fever, and tuberculosis They are single-celled organisms with a cell wall Multiply very quickly Affected by antibiotics

Viruses Smallest microbe Parasites – rely on another organism (the host) for food and to reproduce Not proper cells – have no nucleus nor cell membrane; a strand of DNA wrapped in a protein coat NOT affected by antiobiotics Cause diseases such as influenza, the common cold, measles, chicken pox, and AIDS (HIV)

Fungi Larger than viruses Plant-like but have no chlorophyll Examples include yeast and mould Can be helpful (yeast makes bread rise) and harmful (athlete’s foot and ringworm)

Growing Microbes in the Lab Like all living things, microbes need food to get their energy We can grow them in the lab on a special jelly called agar in a Petri dish Agar jelly contains seaweed If the bacteria are kept warm, they will multiply very rapidly (bacteria can double in number in 20 minutes!)

Why are Steps 4 and 5 so important? 2 6 5 Why are Steps 4 and 5 so important? 3 1 4

Practical – Growing Bacteria We will use a control Needed so we can be sure of the cause; so we can see the difference Acts as a basis for comparison