Aseptic technique (Edexcel GCSE Biology): Revision Notes
Aseptic technique
Aseptic techniques are essential in laboratory settings to prevent contamination of microbial cultures and ensure accurate, safe results. These techniques help maintain a sterile environment when working with microorganisms.
This is how to grow/develop microorganisms without contaminating it with other bacteria/microorganisms:
Sterilisation of Growth Medium and Petri Dishes:
Autoclave:
- An autoclave is a machine that sterilises equipment and growth media using high-pressure steam at around 121°C.
- Petri dishes, culture vials, and growth medium (agar or broth) are placed in the autoclave to kill any unwanted microorganisms that could contaminate the experiment.
- Sterilisation ensures that only the microorganisms being studied will grow in the culture, preventing interference from other microbes.
Use of Sterile Inoculating Loops:
Inoculating Loops:
- An inoculating loop is a tool used to transfer microorganisms from one place to another (e.g., from a culture vial to a petri dish).
- To ensure the loop is sterile, it must be heated in a Bunsen burner flame until it glows red-hot, killing any microorganisms on it.
- After cooling, the sterile inoculating loop can safely be used to transfer microorganisms without introducing contamination.
Keeping Petri Dishes and Culture Vials Covered:
Minimising Exposure to Air:
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Petri dishes and culture vials should be kept covered as much as possible to avoid contamination from airborne microorganisms.
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When working with petri dishes, lids should be lifted only slightly when transferring microorganisms.
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After inoculation, petri dishes are typically sealed with tape or parafilm to prevent contamination while allowing air to enter (for aerobic microorganisms). Sealing the Plates:
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Plates should be sealed but not fully airtight, as some microorganisms require oxygen to grow.
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Sealing the petri dishes also reduces the risk of pathogenic microorganisms escaping into the environment.
Why Aseptic Techniques Are Important:
- Prevent Contamination: Ensures that only the desired microorganism grows and prevents other microbes from contaminating the experiment.
- Safety: Reduces the risk of harmful pathogens being released into the laboratory environment.
- Accurate Results: By preventing contamination, aseptic techniques ensure that the results of the experiment are valid and reliable.
Summary:
In culturing microorganisms, aseptic techniques are vital for maintaining sterile conditions. These techniques include using an autoclave to sterilise growth media and petri dishes, heating inoculating loops to sterilise them before use, and keeping petri dishes covered to avoid contamination. By following these procedures, scientists can ensure their microbial cultures are pure and uncontaminated.