Aseptic techniques

In a nutshell

Aseptic techniques are techniques to follow that prevent contamination from microorganisms in the air and on surfaces.

Aseptic techniques

The table below provides some examples of aseptic techniques.

Technique	Description
Work near a bunsen burner	Working near a bunsen burner will kill airborne microorganisms.
Sterilise equipment	Sterilisation of equipment will kill microorganisms.
Sterilise Petri dishes in an autoclave	An autoclave is a machine that steams equipment at high pressures. Sterilising the Petri dishes will kill microorganisms.
Sterilise the culture media	The culture media (the substance the microorganisms grow on) are sterilised by heating to a high temperature. This will kill any unwanted microorganisms.
Flaming the neck of glass containers	The neck of glass containers should be passed through the flame of the bunsen burner just after they are opened and just before they are closed. Flaming the neck of the glass containers draws air away from the culture as hot air rises. This prevents contamination from unwanted microorganisms.
Sterilising inoculating loops	Inoculating loops should be sterilised in a hot flame and then cooled before being used to transfer microorganisms to the growth medium. If it is not cooled then the bacteria it touches may be killed.
Do not fully open Petri dishes	When the Petri dish is opened, it should only be partly opened to reduce contamination from microorganisms in the air.
Partly seal the lid of the Petri dish	The lid of the Petri dish should be sealed with adhesive tape to stop microorganisms from the air contaminating the plate. However, it shouldn't be completely sealed as this will encourage the growth of anaerobic bacteria that are likely to be pathogens.

Using aseptic techniques

It is very important to use aseptic techniques when you carry out practicals as they prevent contamination from microorganisms in the air and on surfaces.

Biology; Health, disease and the development of medicines; KS4 Year 10; Aseptic techniques

Procedure

1.	Set up a bunsen burner near the work station. Sterilise the Petri dish and growth medium before use.
2.	Sterilise the inoculating loop by passing it through a flame.
3.	Allow the inoculating loop to cool. If it is not cooled enough, the bacteria it touches may be killed.
4.	Flame the neck of the vial containing the bacterial culture after opening it. Dip the loop in bacterial culture and inoculate the growth medium in the Petri dish.
5.	Flame the neck of the vial containing the bacterial culture before closing it.
6.	Glide the inoculating loop over the surface of the agar in the Petri dish. Ensure the Petri dish is open as little as possible to reduce contamination.
7.	Sterilise the inoculating loop by passing it through a flame.
8.	Seal (but not completely) the Petri dish with adhesive tape to prevent contamination from the air. Then culture this at around $25\ \degree C$ .