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1. Mix the components in the order listed. When the medium is added to the DMSO the solution will warm up due to chemical heat.
2. Harvest cells from a culture which is at or near peak density by adding 5 mL ATCC medium 1323 (Page's Balanced Salt Solution) and washing cells into suspension.  Rub the surface of the plate with a spread bar to detach adhering trophozoites.
3. Adjust the concentration of cells to at least 2 x 10⁶/mL in fresh medium.
4. Mix the cell preparation and the cryoprotective solution in equal portions.
5. Dispense in 0.5 mL aliquots into 1.0 - 2.0 mL sterile plastic screw-capped cryules (special plastic vials for cryopreservation).
6. 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.)  
7. Ampules are stored in either the vapor or liquid phase of a nitrogen refrigerator.
8. 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 997.  Distribute the material evenly over the plate using a spread bar.
9. Wrap the entire edge of the plate with parafilm and incubate upright at 20-25°C.
10. Follow the protocol for maintenance of culture.

Page FC. Taxonomic criteria for limax amoebae, with descriptions of 3 new species of Hartmannella and 3 of Vahlkampfia. J. Protozool. 14: 499-521, 1967. PubMed: 6050658

Daggett PM, Nerad TA. The biochemical identification of vahlkampfiid amoebae. J. Protozool. 30: 126-128, 1983. PubMed: 6864593

Page FC. Morphological variation in the cyst wall of Naegleria gruberi (amoebida, vahlkampfiidae). Protistologica 11: 195-204, 1975.

De Jonckheere JF. A Group I intron in the SSUrDNA of some Naegleria spp. demonstrated by polymerase chain reaction amplification. J. Eukaryot. Microbiol. 40: 179-187, 1993. PubMed: 8461891

Adams M, et al. A genetic approach to species criteria in the amoeba genus Naegleria using allozyme electrophoresis. Int. J. Parasitol. 19: 823-834, 1989. PubMed: 2635158

Robinson BS, et al. Discontinuous genetic variation among mesophilic Naegleria isolates: Further evidence that N. gruberi is not a single species. J. Protozool. 39: 702-712, 1992. PubMed: 1453360