Aseptic techniquesSpec 5.17B
In short
Aseptic technique stops unwanted microorganisms getting into a culture and stops the culture escaping. The agar and petri dishes are sterilised in an autoclave, and the inoculating loop is heated in a flame until red hot, then cooled. Lids are lifted only briefly, then taped on, and the dishes are incubated upside down.
To grow (culture) microorganisms safely and get reliable results, you must stop unwanted microorganisms getting in and stop your culture escaping. This is called aseptic technique.
- Use an autoclave to prepare the sterile growth medium (agar jelly) and the petri dishes. An autoclave sterilises equipment using high-pressure steam, which kills microorganisms already present.
- Use a sterile inoculating loop to transfer microorganisms. The loop is sterilised by heating in a flame until red hot, then cooled before use.
- Keep petri dishes and culture vials covered as much as possible. Only lift the lid briefly when transferring microorganisms.
- After inoculating, fix the lid on with tape and incubate the dish upside down.
- Wash your hands and wipe the bench with disinfectant before and after.
Always give the reason. 'Flame the loop to kill any microorganisms on it, so the culture is not contaminated' scores; just 'flame the loop' does not.
Written and checked against the Edexcel GCSE Biology (1BI0) specification · Updated October 2026