Cryoprotective Solution
DMSO, 2.0 ml
Fresh growth medium w/o bacteria, 8.0 ml

Harvest and Preservation

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 that is at or near peak density by filtration and centrifugation at 800 x g for 5 min.
3. Adjust the concentration of cells 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, do not leave in water bath, aseptically remove the contents of the ampule and inoculate into a T-25 tissue culture flask containing 10 ml of an equal-parts mixture of ATCC medium 1525 and either ATCC medium 1405 or ATCC medium 1361, bacterized with Klebsiella pneumoniae subsp. pneumoniae (ATCC® 700831™) or Enterobacter aerogenes (ATCC® 13048™).
9. Incubate at 15°C with the cap screwed on tightly.
10. Once the culture is established, vigorously agitate the flask and aseptically transfer 0.5 ml to 10.0 ml of bacterized ATCC medium 1525.
11. Follow the protocol for maintenance of culture.

Leadbeater BS. Developmental studies on the loricate choanoflagellate Stephanoeca diplocostata Ellis. V. The cytoskeleton and the effects of microtubule poisons. Protoplasma 136: 1-15, 1987.

Leadbeater BS. Developmental studies on the loricate choanoflagellate Stephanoeca diplocostata Ellis VI. Effects of silica replenishment on silica impovershed cells. Protoplasma 153: 71-84, 1989.

Leadbeater BS. Developmental studies on the loricate choanoflagellate Stephanoeca diplocostata Ellis I. Ultrastructure of the non-dividing cell and costal strip production. Protoplasma 98: 241-262, 1979.

Leadbeater BS. Developmental studies on the loricate choanoflagellate Stephanoeca diplocostat Ellis IV. Effects of silica deprivation on growth and lorica production. Protoplasma 127: 171-179, 1985.

Leadbeater BS. Developmental studies on the loricate choanoflagellate Stephanoeca diplocostata Ellis. VII. Dynamics of costal strip accumulation and lorica assembly. Eur. J. Protistol. 30: 111-124, 1994.

Carr M, et al. Molecular phylogeny of choanoflagellates, the sister group to Metazoa. Proc. Natl. Acad. Sci. USA. 105: 16641-16646, 2008. PubMed: 18922774