1. If a specific transfer procedure is described for a certain cell line this procedure has to be followed for routine culture transfer to fresh medium.

2. For all other cultures the transfer to fresh medium is done as follows:

2.1. At the beginning of every working day those parts of the necessary instruments (normally forceps and scalpel) that may come into contact with the cell material are heated up once to red heat and cooled and stored in 70 % ethanol.

2.1. The petri dishes containing callus that should be transferred to fresh medium are placed under the sterile laminar air flow in the clean bench.

2.2. The petri dishes are carefully wrapped out of the parafilm without turning them upside down.

2.3. Forceps and scalpel are taken out of the 70 % ethanol and heated up until the ethanol has evaporated completely.

2.4 The instruments are cooled to normal (not above 40 °C) temperature in the agar of a petri dish containing fresh medium.

2.5.1. In case of soft callus some pieces of callus are picked up from the old petri dish and placed onto the petri dish containing fresh medium. The callus has to be placed gently onto the fresh medium. The callus material should not be pressed. The callus material should not be placed upside down onto the fresh medium. The callus material should be disrupted only to an extent which cannot be avoided.

2.5.2. In case of very rigid callus, the callus has to be sliced into pieces using a scalpel. Preferentially the surface parts of the old callus should be removed from the rotten bottom parts and transferred to fresh medium. The callus material should not be compressed. The callus material should not be placed upside down onto the fresh medium. The callus material should be disrupted only to an extent which cannot be avoided.

2.6 After the callus transfer the inoculated petri dishes are closed and wrapped up carefully with parafilm. (During wrapping up with parafilm the freshly transferred callus material should not fall off from the medium.)