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Introduction
Micro-organisms are microscopic in size and can only be seen with the aid of a microscope. Colonies of millions an be seen with the naked eye. Micro-organisms can be either unicellular (one cell) or multi-cellular (many cells). There are three types of micro-organisms:


• Bacteria
• Fungi
• Viruses
Micro-organisms can be disease-causing (pathogens) or beneficial to people, e.g. help to produce drugs.

Bacteria
There are thousands of different types of bacteria. Bacteria are cells which contain a chromosome. The cell chromosome (control centre) cytoplasm (fluid) is mainly cytoplasm and some bacteria have a flagellum (tail) for movement. The control centre for the bacterium is the chromosome.
Bacteria

Fungi
Fungi are a large group of micro-organisms, which includes moulds, toadstools, mushrooms and yeast. spores Fungi do not make their own food and are saprophytic. This means they live off dead or living creatures. Fungi can be harmful and helpful as they break down spore case dead organisms. They can be helpful as we can create i antibiotics from them. They can be harmful as they can cause disease, e.g. athletes foot.
Fungus

Viruses
Viruses are extremely small micro-organisms. They are said to be on the fringe of life. Most scientific opinions states that viruses are not cells and therefore not alive. A virus is a series of genes inside a protein sheath. Viruses do not eat but simply reproduce by taking over living cells. There are thousands of different viruses and they are always pathogenic as they damage healthy cells. ‘Examples of viruses are: Corona, Flu, AIDS, Bird Flu.
Virus

Life Processes of a Bacterium

Feeding
Bacteria feed by secreting enzymes. These enzymes digest living or dead organisms. The digested materials are then absorbed into the bacterium.

Reproduction
Bacteria reproduce by dividing into two. The chromosome is duplicated and then the bacterium splits into half.
This process is called binary fission.

Excretion
The waste materials produced by the bacterium diffuse out through the cell membrane into the surroundings. These materials can be toxic to the host that contains the bacteria.

Respiration
Some bacteria can process food by aerobic respiration (in the presence of oxygen). Other bacteria can process food anaerobically (without requiring oxygen). Both processes release energy.

Survival
When conditions become adverse a bacterium won’t survive. Because of this a bacterium can form a spore which can survive for many years. The spore will form a bacterium when they encounter dead or living material under the right conditions. For example the bacteria require adequate temperature and moisture.