# Describe how aseptic techniques are used when culturing microorganisms in a school laboratory. Explain why each precaution is necessary.

> WJEC A-Level Biology (Wales) — 3.3 Microbiology · Describe · 5 marks

> A student wants to grow a culture of bacteria on an agar plate in the school laboratory. Before beginning, the student is reminded to follow aseptic techniques throughout the procedure.

## Mark scheme (5 marks)

1. Sterilise / autoclave the growth medium (agar) and equipment before use
2. Work near a Bunsen burner flame (or in a laminar flow cabinet) to create an upward current of air that prevents airborne microorganisms from settling
3. Pass the inoculating loop / neck of the culture bottle through the Bunsen flame to sterilise it before use
4. Seal the agar plate with tape / partially seal the lid after inoculation to prevent contamination from the environment
5. Incubate at a temperature no higher than 25 °C to reduce the risk of culturing pathogens that could be harmful to humans

## Key terms

- [aseptic techniques](https://www.gradenine.co.uk/glossary/aseptic-techniques)
- [microorganisms](https://www.gradenine.co.uk/glossary/microorganisms)

## Related

- [Revision notes for WJEC A-Level Biology (Wales)](https://www.gradenine.co.uk/learn)
- [How to answer "Describe" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
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Source: [GradeNine](https://www.gradenine.co.uk/q/describe-how-aseptic-techniques-are-used-e53c561b) · Published by Druglandscape Ltd.