1. Allow the cells to encyst.  To detach cysts from the plate flush the surface with 5 mL fresh ATCC medium 1323 (Page's Balanced Salt Solution).  Rub the surface of the plate with a spread bar to detach adhering cysts.
2. Transfer the liquid medium to a sterile centrifuge tube.
3. If the cyst concentration does not exceed 2 x 10⁶ cysts/mL adjust the suspension to that concentration.  To adjust the concentration, centrifuge at 600 x g for 5 min and resuspend the pellet in the volume of fresh medium required to yield 2 x 10⁶.
4. While cells are centrifuging prepare a 15% (v/v) solution of sterile DMSO as follows:  Add the required volume of DMSO to a glass screw-capped test tube and place it in an ice bath.  Allow the DMSO to solidify.  Add the required volume of refrigerated medium.  Dissolve the DMSO by inverting the tube several times.  *NOTE: If the DMSO solution is not prepared on ice, an exothermic reaction will occur that may precipitate certain components of the medium.
5. Mix the cell preparation and the DMSO in equal portions. Thus, the final concentration will be at least 10⁶ cysts/mL and 7.5% (v/v) DMSO.  The equilibration time (the time between addition of DMSO and the start of the cooling cycle) should be no less than 15 min and no longer than 30 min.
6. Dispense in 0.5 mL aliquots into 1.0 - 2.0 mL sterile plastic screw-capped cryules (special plastic vials for cryopreservation).
7. Place the vials in a controlled rate freezing unit.  From room temperature cool at -1°C/min to -40°C.  If the freezing unit can compensate for the heat of fusion, maintain rate at -1°C/min through the heat of fusion.  At -40°C plunge 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.)  
8. The frozen preparations are stored in either the vapor or liquid phase of a nitrogen freezer.
9. To establish a culture from the frozen state place an ampule in a water bath set at 35°C (2-3 min). Immerse the vial to a level just above the surface of the frozen material. Do not agitate the vial.
10. Immediately after thawing, aseptically remove the contents of the ampule and distribute to the center of a fresh plate of ATCC medium 711.  Distribute the material evenly over the plate using a spread bar.  Incubate at 25°C.

Gast RJ, et al. Subgenus systematics of Acanthamoeba: Four nuclear 18S rDNA sequence types. J. Eukaryot. Microbiol. 43: 498-504, 1996. PubMed: 8976608

Gautom RK, et al. Mitochondrial DNA fingerprinting of Acanthamoeba spp. isolated from clinical and environmental sources. J. Clin. Microbiol. 32: 1070-1073, 1994. PubMed: 7913095

John DTOpportunistically pathogenic free-living amebaeIn: John DTParasitic protozoa2nd ed.3San DiegoAcademic Presspp. 143-246, 1993

Kilvington S, Beeching J. Development of a PCR for identification of Naegleria fowleri from the environment. Appl. Environ. Microbiol. 61: 3764-3767, 1995. PubMed: 7487014

Singh BN. Nuclear division in nine species of small free-living amoebae and its bearing on the classification of the order amoebida. Philos. Trans. R. Soc. Lond. B Biol. Sci. London., 2: 405-460, 1951.

Fritsche TR, et al. Occurrence of bacterial endosymbionts in Acanthamoeba spp. isolated from corneal and environmental specimens and contact lenses. J. Clin. Microbiol. 31: 1122-1126, 1993. PubMed: 8501212

Howe D, et al. Identification of two genetic markers that distinguish pathogenic and nonpathogenic strains of Acanthamoeba spp.. Parasitol. Res. 83: 435-348, 1997. PubMed: 9197389

Stothard DR, et al. The evolutionary history of the genus Acanthamoeba and the identification of eight new 18S rRNA gene sequence types. J. Eukaryot. Microbiol. 45: 45-54, 1998. PubMed: 9495032

Stothard DR, et al. Fluorescent oligonucleotide probes for clinical and environmental detection of Acanthamoeba and the T4 18S rRNA gene sequence type. J. Clin. Microbiol. 37: 2687-2693, 1999. PubMed: 10405422

Kong HH, et al. Mitochondrial DNA restriction fragment length polymorphism (RFLP) and 18S small-subunit ribosomal DNA PCR-RFLP analyses of Acanthamoeba isolated from contact lens storage cases of residents in southwestern Korea. J. Clin. Microbiol. 40: 1199-1206, 2002. PubMed: 11923331

Marciano-Cabral F, Cabral G. Acanthamoeba spp. as agents of disease in humans. Clin. Microbiol. Rev. 16: 273-307, 2003. PubMed: 12692099