# A student is culturing bacteria on an agar plate in a school laboratory. Describe the aseptic techniques the student should use when culturing the bacteria, and explain why each technique is important.

> Edexcel A-Level Biology A: Salters-Nuffield (9BN0) — 5.1 Microbial growth and culture · Describe · 5 marks

> A student is growing a culture of bacteria on an agar plate. They must follow aseptic techniques to ensure the culture is not contaminated and that no harmful microorganisms are released into the environment.

## Mark scheme (5 marks)

1. The inoculating loop / equipment must be sterilised, e.g. by passing it through a flame or using an autoclave
2. Sterilising equipment prevents contamination of the culture with unwanted microorganisms / prevents introduction of foreign bacteria
3. The agar plate / growth medium should be sterilised before use, e.g. using an autoclave, to kill any pre-existing microorganisms
4. The Petri dish lid should be lifted as little as possible / taped down / only partially opened when inoculating
5. Working near a Bunsen burner flame / in sterile conditions reduces airborne contamination because the rising hot air prevents microorganisms from settling onto the plate

## Key terms

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

## Related

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Source: [GradeNine](https://www.gradenine.co.uk/q/a-student-is-culturing-bacteria-on-12439cc5) · Published by Druglandscape Ltd.