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Harmful Microorganisms 11.1 What are microorganisms? • • • • • Also known as microbes Very very small living things Bacteria, fungi and viruses 100 times smaller than a human cell Most cause no harm to animals and plants Staphylococcus aureus A common microbe living on human skin and is usually harmless Microscope • How do we see very small things? • http://www.bbc.co.uk/learningzone/clips/micr oscopy/13526.html Microorganism • Micro • Organism Greek word meaning small living thing • http://www.bbc.co.uk/learningzone/clips/und erstanding-the-size-of-bacteria/2279.html Microbes and the Human Body • http://www.bbc.co.uk/learningzone/clips/micr obes-and-the-human-body/207.html Pathogens • Microorganisms that cause disease when they enter the body. • Pathogens are studied by Microbiologists. • A cluster of Escherichia coli Bacteria magnified 10,000 times • 1µm = 1 millionth of a metre • Can cause disease to a plant or animal. Human Pathogens Bacteria • Has a cell wall and cell membrane • No nucleus • Genetic material floats around in the cytoplasm • Larger than a virus • Cholera • Typhoid • Tuberculosis Virus • Has a protein coat • No nucleus • A few genes that float around inside the virus • Smaller than bacteria • Measles • Rubella • Mumps • Polio How do pathogens make you feel ill? Bacteria • They damage your cells • E.g. lung tissue is destroyed by tuberculosis bacteria • They produce toxins – poisonous chemicals. • E.g salmonella bacteria produce a toxin that causes food poisoning Virus • They get inside your cells and damage them Flu: influenza viruses invade and take over the epithelial cells lining the respiratory tract, proliferate rapidly and then infect other cells Reproduction of bacteria and viruses • Time delay between the harmful microorganisms entering a body and feeling unwell. • Incubation period • Reproduce rapidly during this time. • http://www.bbc.co.uk/learningzone/clips/bact erial-growth/209.html Reproduction differences bacteria • Reproduce quickly • Split every 20 minutes • Within a few hours will be several thousand • Now start to have a big effect on your body • http://www.bbc.co.uk/learn ingzone/clips/the-bacterialiving-on-ourskin/2281.html virus • Cannot replicate by themselves • Take over and use cells to make more virus particles. • http://www.bbc.co.uk/learn ingzone/clips/what-arevaccines-and-how-quicklycan-they-bemade/7134.html Bacteria Virus Key points • Bacteria, fungi and viruses are three groups of microorganisms • Pathogens are microorganisms which cause a disease in a plant or an animal • Bacteria cause disease by damaging cells or producing toxins • Viruses cause disease by damaging cells.
