Question

1. Evaluate the virtues of flaming the cotton plug of test tubes and putting out the burning cotton with the hand before transferring cultures, a procedure advocated by some.
2. Evaluate the virtues of the method of transfer of cultures in which both tubes are opened at once, with the plugs held between the fingers, against the procedure in which only one tube is opened at a time.

Answer 1

1. This is to avoid contamination of the culture or medium inside the test tube. The cotton plug that go inner side of the test tube must be sterile while keeping it back to avoid contamination.

2 This is to reduce the time of exposure to contamination.Always handle open tubes at an angle; never let them point directly up, as airborne or other environmental organisms could fall into the tube and cause contamination. Also, keep the lids of plates over the plate when streaking, as this will help prevent environmental contamination of the plate.