Biology Module 3 - Microbiology

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Growing Microbes

  • Microbiology is the study of micro-organisms. They are tiny living organisms such as bacteria, viruses, fungi which are usually too small to be seen with a naked eye. 
  • To see them, a microscope should be used. 
  • Why do we study them? - they are important in decay and the recycling on nutrients in the environment. 
  • - they can cause disease and they are useful to people.
  • Many can be grown in a lab which helps us learn things about them, we can find out what nutrients they need and what chemicals kill them. We can see which are helpful and which cause severe diseases.

What do Microbes need to grow?

  • To find out about them = culture them (grow loads so you can see a colony)
  • To culture : give them everything they need, this usually includes carbohydrate to act as an energy source, along with this, various mineral ions and sometimes, proteins and vitamins.
  • The nutrients are often contained in an agar medium. Agar is a substance which dissolves in hot water and forms a jelly. You pour hot agar into a petri dish. Then leave it to cool before adding any micro-organisms. 
  • Other way : provide nutrients to grow micro-organisms is as a broth in a culture flask. You need to provide oxygen and water as well. 

Safety Precautions in the lab

  • Always a risk of mutation may happen which results in a new and dangerous pathogen. The culture may be contaminated by diseased pathogens in the soil, air or water. 
  • Pure strains of bacteria also need to be kept from other micro-organisms. There are millions of microbes, some harmful and some not. 
  • Safety precautions should be used to avoid the growth of harmful pathogens. 

Food production using Yeast

  • Yeasts are single celled organisms, each yeast cell has a nucleus, cytoplasm, membrane and wall. 
  • The main way in which yeasts reproduce is through asexual budding - splitting in two to form new yeast cells. 
  • When they have plenty of oxygen, they respire aerobically. They break down sugar to provide energy for cells, making water and carbon dioxide as waste products.
  • But, it can also respire anaerobically. When the cells break down, sugar in the absence of oxygen, they produce ethanol and carbon dioxide.
  • Ethanol (alcohol) - this anaerobic respiration of yeast is also called fermentation.
  • The yeast cells need aerobic respiration because it makes more energy than anaerobic. This lets them grow and reproduce, but once there is a large number of yeast cells, they can survive for a long time in low oxygen conditions. They break down sugar to make ethanol.
  • Yeast can be used to make bread, alcoholic drinks. It was used to make bread in Egypt ; 6000 years ago. Some was found in Iran ; 7000 years old.

Making Alcoholic Drinks

  • Beer making depends on malting. This is when you soak barley grains in water to keep them warm. As germination begins, enzymes break down the starch in the barley grains into…



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