Sterile technique is used to ensure a "clean" lab environment. It is essential to ensure the reliability of experimental results.

Sterile practices are especially important when working with microorganisms. A single spore or tiny bacterium can overgrow your whole medium and destroy your experiment.

The following steps are used to keep laboratory work sterile:

  • Laboratory doors and windows are kept closed to prevent air currents, preventing surface microorganisms becoming airborne.

  • The wire loop and glass spreader are sterilized before and after use with a Bunsen burner to prevent the introduction of unwanted microorganisms.

  • Lids from bottles and tubes are held when removed, and not placed on the bench during material transfer from one bottle or tube to another.

  • The neck of a bottle or tube must be immediately heated using the Bunsen burner so that any air movement is outward.

  • The bottle or tube are opened for the minimum time possible, and while open, all work is performed close to the Bunsen burner flame.

  • Media and equipment are sterilized to prevent the growth of unwanted microorganisms.

There are two images: on the left, a contaminated petri dish that contains many fuzzy white and green fungal growths. On the right, the opening rim of a glass bottle containing an orange liquid is passed through a blue bunsen burner flame to sterilize it.

Figures 1: Left- A contaminated petri dish. Various species of fungi have grown in this petri dish. Right- Sterile technique used in material transfer from the bottle. The neck of the bottle is heat-sterilized by the Bunsen burner flame.