MICROORGANISMS AND BIOTECHNOLOGY

Transcription

1 MICROORGANISMS AND BIOTECHNOLOGY

2 Lesson 1 Learning Objective 1.List the main characteristics of viruses. Outline Microorganisms Virus Characteristics Life cycle Reaction of host to viral infection AIDS

3 Tiny organisms that are studied with the aid of a microscope. Microorganisms

4 Microorganisms Microorganisms are usually made up of one cell only (unicellular). They are found in all living things. Some of them, pathogens, can be harmful and causes disease. But there are some microorganisms that are needed for living things to survive.

5 Humans need some microorganisms to stay alive. They can help us digest food and develop our immune system. Pathogens can enter the body through the skin, through respiratory system, through food or water and by vectors (e.g. mosquitoes, saliva of dogs).

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7 MICROORGANISMS Viruses Bacteria Fungi

8 Viruses Characteristics: Extremely small (visible under electron microscope). It is composed of nucleic acid core (DNA or RNA), surrounded by a protein coat (capsid).

9 Viruses No protoplasm and cell organelles. No organisation of a cell. Do not need food for energy. Do not feed, respire, excrete or grow. Reproduce only when it is inside the cells of living organisms (host cell).

10 Viruses All viruses are parasites. They can infect bacteria, plants and animals. Each type of virus shows great specificity for the type of host it infects. Outside the host, viruses are dormant and exist as crystals. All viruses can cause disease and so are said to be pathogenic. Common cold, influenza, measles, chicken pox and AIDS.

11 Viruses Viruses can only multiply inside cells. No drugs and antibiotics can get to them. But our body can manufacture a chemical called 'interferon' which can help prevent the cells from being infected by viruses. Interferon can be produced in laboratory to treat viral infection. Vaccines are used to prevent diseases such as smallpox and measles. No successful vaccine for AIDS yet.

12 Life cycle of a virus E.g. Bacteriophage Bacteriophage (bacteria-eaters) is a type of virus that infects bacteria. It consists of a head, shaped like crystal, with a rod-like projection. The head contains a strand of DNA.

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14 Reaction of host to viral infection When viruses infect cells, they cannot carry out their normal functions and disease symptoms appear. Therefore, viruses are agents of disease. They can cause many diseases (AIDS is caused by HIV). The human body can protect itself from viruses. Viral infection stimulates certain reactions in the body. Immune response Production of interferon

15 Immune response Lymphocytes attack and destroy infected cell, or produce antibodies to destroy viruses. HIV cannot be destroyed because it destroys the human immune response. Vaccines are available for certain disease, e.g measles and poliomyelitis, to stimulate the production of antibodies against the disease without causing the disease. Production of interferon A group of proteins produced by cells when challenged by a virus. It is carried in the blood, inhibiting the virus multiplication and virus infection in uninfected cells.

16 AIDS Acquired Immune Deficiency Syndrome Cause Human immunodeficiency virus (HIV) Signs and symptoms Loss of body weight Chronic diarrhoea Prolonged fever Persistent cough Skin problem

17 AIDS Effects Loss of natural immunity to disease so that the patient succumbs readily to diseases Treatment No known cure at present.

18 AIDS Transmission Through intimate sexual contact with infected person. Through infected blood. From an infected mother to her baby through pregnancy or childbirth. Preventive methods Avoid intimate social contact with infected person. Using a condom may reduce the risk of infection. Avoid getting infected blood into your blood system. Infected females should avoid getting pregnant.

19 Other viral disease Disease How transmitted Symptoms Preventative measures Other points Influenza Droplets in air Fever, headache, muscular pains. Vaccine New strains of the virus keep appearing, so vaccines have limited use. Smallpox Droplets in air or contact with skin Fever, dark red spots which turn into scabs. Vaccine A world-wide campaign has now eradicated smallpox. Chickenpox Droplets in air or contact with skin Fever, itchy blisters which turn into scabs. Vaccine Almost everyone gets chickenpox by adulthood.