1.1.28

Avoiding Contamination

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Aseptic Technique

To prevent contamination (from skin, air, soil, or water), aseptic (free from contamination) techniques are used on all apparatus. These techniques kill and prevents the entry of unwanted bacteria. They involve:

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Flames

  • Inoculation loops (tools used to transfer bacteria) must be passed through a flame for sterilisation (removes bacteria).
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Boiling

  • Solutions and agar must be boiled for sterilisation.
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Lids

  • To stop air from getting into the Petri dish, the lid must be rapidly taken off and put back on when using the inoculating loop to add bacteria to the agar.
  • This lid should be taped on and the dish should be stored upside down to prevent condensation forming on the lid and then dripping onto the agar.
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Temperature

  • In schools, the maximum temperature at which cultures should be incubated (stored) is 25 degrees Celsius.
  • This extra precaution reduces the risk of harmful bacteria growing.

Jump to other topics

1Cell Biology

1.1What's in Cells?

1.2Cell Division

1.3Transport in Cells

2Organisation

2.1Principles of Organisation

2.2Enzymes

2.3Circulatory System

2.4Non-Communicable Diseases

2.5Plant Tissues, Organs & Systems

3Infection & Response

4Bioenergetics

5Homeostasis & Response

5.1Homeostasis

5.2The Human Nervous System

5.3Hormonal Coordination in Humans

5.4Plant Hormones

6Inheritance, Variation & Evolution

7Ecology

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