DMSO, 2.0 mL
Filtered artificial seawater (or similar), 8.0 mL
Harvest and Preservation
- Mix the components in the order listed. When the medium is added to the DMSO the solution will warm up due to chemical heat.
- Harvest cells from a culture which is at or near peak density by adding 5 mL sterile filtered artificial seawater and washing cells into suspension. Rub the surface of the plate with a spread bar to detach adhering trophozoites.
- Adjust the concentration of cells to at least 2 x 106/mL in fresh medium.
- Mix the cell preparation and the cryoprotective solution in equal portions.
- Dispense in 0.5 mL aliquots into 1.0 - 2.0 mL sterile plastic screw-capped cryules (special plastic vials for cryopreservation).
- Place vials in a controlled rate freezing unit. From room temperature cool at -1°C/min to -40°C. If freezing unit can compensate for the heat of fusion, maintain rate at -1 C/min through heat of fusion. At -40°C plunge ampules into liquid nitrogen. Alternatively, place the vials in a Nalgene 1°C freezing apparatus. Place the apparatus at -80°C for 1.5 to 2 hours and then plunge ampules into liquid nitrogen. (The cooling rate in this apparatus is approximately -1°C/min.)
- Ampules are stored in either the vapor or liquid phase of a nitrogen refrigerator.
- To establish a culture from the frozen state place the vial in a 35°C water bath. Immerse the vial to a level just above the surface of the frozen material. Do not agitate the vial. Immediately after thawing, aseptically transfer the contents of the ampule to the center of a fresh plate of ATCC medium 994. Distribute the material evenly over the plate using a spread bar.
- Wrap the entire edge of the plate with parafilm and incubate upright at 25°C.
- Follow the protocol for maintenance of culture.