Boston University 2006:Quigen Glycerol stock protocol
From The Quiagen Bench Guide (pg. 6):
E. coli strains can be stored for many years at –70°C in medium containing 15% glycerol.
Prepare glycerol stocks of bacteria as follows:
- Add 0.15 ml glycerol (100%) to a 2 ml screw-cap vial and sterilize by autoclaving.
TIP: Vials of sterilized glycerol can be prepared in batches and stored at room temperature until required.
- Add 0.85 ml of a logarithmic-phase E. coli culture (see “Growth of E. coli cultures”, page 7) to the vial of pre-sterilized glycerol.
- Vortex the vial vigorously to ensure even mixing of the bacterial culture and the glycerol.
- Freeze in an dry ice–ethanol bath or liquid nitrogen and store at –70°C.
TIP: Avoid repeated thawing and re-freezing of glycerol stocks as this can reduce the viability of the bacteria.
TIP: For precious strains, storage of two stock vials is recommended.