article : How we know about Aseptic Technique

You will be working with many pathogenic species of bacteria in the laboratory. Therefore, you must learn to use careful aseptic technique at all times, both to protect self, and classmates, and to avoid contaminating cultures.

Remember that bacteria are in the air as well as on skin, the counter, and all objects and equipment that have not been sterilized.

The most important tool for transferring cultures is the wire inoculating needle or loop. It can be quickly sterilized by heating it to red hot in a bunsen burner flame. Adjust the air inlets of the burner so that there is a hotter inner cone and the outer, cooler flame. A dry needle may be sterilized by holding it at a 30^o angle in the outer part of the flame. A wet loop with bacteria on it should first be held in the inner part of the flame to avoid spattering, and then heated until red hot in the outer part of the flame. Always flame the loop immediately before and after use! Allow it to cool before picking up an inoculum of bacteria. If the loop spatters in the agar or broth, it is too hot. Hold the loop or wire handle like a pencil.