Micro-organisms are very small living things, so small that you need a microscope to be able to see them.There are four types of micro-organisms (or microbes as they are often called), some are useful to us whilst others are harmful:
1. Bacteria: these are single celled micro-organisms which grow well by themselves if they are given a food source and appropriate heat. Some bacteria can cause dieseases and once inside the body they can reproduce quickly. Other bacteria are not harmful and can be used in food production such as bread, alcoholic drinks, cheese and yohhurt. Bacteria that cause illnesses can be passed on from one person to another.
2. Fungi: is an organism such as yeast, mould and mushrooms. Again whilst some fungi are poisonous to humans others are not and are eaten for food.
3. Protozoa: are single celled organisms that live either in water or in damp places. Some can cause disease.
4. Viruses: these are much smaller than bacteria and are parasitic which means they multiply only when inside a host. Many viruses cause illness as they interfere with its normal operation.Outside the host viruses are inactive and do not reproduce. Viruses, like bacteria can be passed on from one person to another.
