Aseptic technique

Contamination routes (how unwanted organisms get in):

• Air currents carrying dust and microbes onto an open plate
• Skin contact from touching the agar or the loop tip
• Talking, coughing, or breathing over an open plate
• Unsterilized tools, like a loop that was not flamed

Aseptic technique, in order:

1. Clean the work surface and wash your hands, then put on gloves.

2. Light the burner and work in the rising warm air near the flame.

3. Flame the inoculating loop until it glows, then let it cool a few seconds.

4. Lift the plate lid only partway and only for as long as you need.

5. Streak the sample, then close the lid right away.

6. Re-flame the loop before setting it down so nothing is carried out.

Why minimize open time: Every second a plate is open, airborne microbes can settle on the agar. Keeping it open as briefly as possible lowers the chance that anything other than my sample starts growing.

Safety rule for cultures and waste: Treat every culture as if it could be harmful. Never open an incubated plate at your seat, and dispose of plates and used tools in the marked biohazard container, never the regular trash.

Prediction: A clean plate will show only one kind of colony along my streak lines. A contaminated plate will show extra colonies of different colors or shapes, often in spots where I did not streak.