Notes
- A common technique to preserve E. Coli containing specific plasmids (and other bacterial) longer term.
- While it is possible to make a long term stock from cells in stationary phase, ideally your culture should be in the logarithmic growth phase.
Source
Standard lab technique – handed down from Postdoc to student.
Materials
- 1:1 glycerol/water solution (preferably be autoclaved)
- Cryogenic vials or (1.5 – 2µL) Eppendorf tubes – Screw caps preferred if snap-freezing in liquid N2 to avoid the risk of the lids coming off.
- LN2 – if at hand, cells are still recoverable even without, but slow-freeze can rupture the cells and reduces viability.
Method
- Add 0.7 – 1 ml of 50% glycerol in H2O to a tube.
- Add 0.7 – 1 ml sample from the culture of bacteria to be stored.
- Gently vortex the tube to ensure the culture and glycerol is well-mixed. Alternatively, pipet to mix.
- Use a tough spot sticker to put the name of the strain or some useful identifier on the top of the vial.
- On the side of the vial list all relevant information – part, vector, strain, date, researcher, etc.
- Snap-freeze in LN2 – if possible, does work without.
- Store in a freezer box in a -80°C freezer. Remember to record where the vial is stored for fast retrieval later.