Question

1. Why can't we store viable cultures st room temperature for extended periods?
2. Why is it better to maintain stock cultures at low temperatures than to frequently subculture actively growing cultures?
3. How long can microorganisms remain viable in a freeze-dried state?

Answer 1

1)At low enough temperatures, any enzymatic or chemical activity which might cause damage to the biological material in question is effectively stopped. While at room temperature the cell activity will be kept on and ultimately will die. Cryopreservation methods seek to reach low temperatures without causing additional damage caused by the formation of ice crystals during freezing.

2)Storing cells by freezing is important to store cells for future studies. Cryopreservation ensures that you have back-up cells in case of contamination and loss of cell supply. It is best to cryopreserve cells when they are at their maximum growth rate or almost confluent.

Apart from maintaining them regularly which require extra efforts for culturing and resource consumption it is better to preserve.

3 ) The preservation of cells is an extremely important aspect of cell culture. The only effective means of preservation of animal cells is by freezing, which can be accomplished with either liquid nitrogen or by employing cryogenic freezers. The freezing process involves slowly reducing the temperature of prepared cells to -30 to -60°C followed by a transfer to temperatures less than -130°C. Once at ultralow temperatures, the cells are biologically inert and can be preserved for years.