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Transcript
Unit 1 – Living Cells • Topic 2 – Microbes! 1. Types of Microbes 2. Controlling the growth of microbes 3. Microbes in industry Controlling the growth of microbes LEARNING OUTCOMES • Name 2 characteristics about how microbes grow and reproduce • State what antibiotics do • State what antifungals do • State what antivirals do Think / Pair / Share • You have seen microbes grow on agar dishes • These dishes have now been destroyed • What would happen to the microbes if we left them in the incubator? • Why do you think we should control how microbes grow? • How do you think we can do control the growth of microbes? Microbial Growth • Microbes, such as bacteria and yeast, have many characteristics that help them to reproduce, such as being able to reproduce asexually and grow rapidly. • http://www.youtube.com/watch?v=gEwz DydciWc Controlling the growth of Microbes 1 • Microbes need a suitable temperature to reproduce. • Placing microbes in cold temperatures (fridge) slow down the growth of microbes. • Placing microbes in very hot temperatures (oven) can destroy microbes. Controlling the growth of Microbes 2 Special chemicals can be used to PREVENT the microbes from growing any further. These chemicals can be found in: • cleaning products such as bleach or disinfectant or • in medicinal products like: – AntiBiotics are used to treat Bacterial infections (bacteria) – AntiVirals are used to treat Viral infections (viruses) – AntiFungals are used to treat Fungal infections (fungi) Alexander Fleming (1881 –1955) • The Discovery of Penicillin and Antibiotics VIDEO (2.20 mins) • http://www.youtube.com/watch?v=tMPY -zf8X94 Alexander Fleming (1881 –1955) • Alexander Fleming accidentally discovered penicillin (an antibiotic) • He was throwing out old mouldy bacterial cultures when he noticed that they had clear areas around the mould • He concluded that the mould was secreting a chemical that was killing the bacteria • He isolated the chemical • The mould was called Penicillium so he called the substance penicillin • Fleming’s discovery led to the discovery of many similar substances – we now call them antibiotics. Antibiotic Disk • Bacteria can be grown all over nutrient agar in a petri dish • Then an antibiotic can be added. Antibiotics stop bacteria from growing. Antibiotic NO bacteria growing Bacteria growing Clear zone (NO bacteria growing) Bacteria growing Diameter of clear zone Antibiotic Multi-disks • We can use SEVERAL antibiotics to see which one is more effective at stopping the growth of bacteria. Antibiotic Multi-disks Aim: To investigate… Which antibiotic is more effective at stopping the growth of bacteria Measurements to be made: The diameter of the clear zone, in cm, using a ruler Antibiotic Multi-disks Results: Conclusion: (answer your aim and link in your results) Antibiotic Multi-disks Results: Antibiotic Diameter of CLEAR ZONE (cm) P 0 S TE C E G Conclusion: 0 Antibiotic ____ was the most effective at stopping the growth of the bacteria because it had the ______ clear zone. Controlling the growth of microbes LEARNING OUTCOMES • Name 2 characteristics about how microbes grow and reproduce • State what antibiotics do • State what antifungals do • State what antivirals do Controlling the growth of microbes LEARNING OUTCOMES • Explain what is meant by ‘resistant’ bacteria • Explain what is meant by ‘sensitive’ bacteria Resistant Vs Sensitive bacteria Region of bacterial growth (Bacteria is resistant here) Region of no bacterial growth (Bacteria is sensitive here) • Not all antibiotics are as effective as each other. • What is the best antibiotic? • What are the worst antibiotics? • ‘best’ and ‘worst’ are not scientific terms. • Instead we can use ‘resistant’ and ‘sensitive’ Resistant Vs Sensitive bacteria • If bacteria is prevented from growing it is said to be sensitive to the antibiotic • And if the bacteria is not affected it is said to resistant to the antibiotic. • From the antibiotic multi disk diagram, – the bacteria is resistant to antibiotics _______ P and E – And the bacteria is sensitive to antibiotics _______ G, S, C and TE Resistant Bacteria • Resistant bacteria are not killed by antibiotics. • This is because the bacteria are too ‘strong’ to be destroyed. • More and more bacteria are becoming resistant to antibiotics. • The main reason is because we over-use them! Antibiotics / destroyed / resistant / over-use Controlling the growth of microbes LEARNING OUTCOMES • Explain what is meant by ‘resistant’ bacteria • Explain what is meant by ‘sensitive’ bacteria