A Simple and Rapid Cryopreservation Technique for Ciliates: A Long-Term Storage Procedure Used for Marine Scuticociliates

Pseudocohnilembus persalinus is a free-living marine scuticociliate that, as a new model organism, has been used in a wide variety of studies. However, long-term laboratory maintenance for this species is mainly achieved by subculture that requires rigorous culture environments and, too often, cultures of the organism die out for a variety of reasons. Successful transport of viable cultures also poses problems for researchers. This study describes a simple and rapid protocol for long-term cryopreservation of P. persalinus. The effects of physiological states of individuals before freezing, the type and concentration of cryoprotectant, and optimal temperatures for freezing and thawing were assessed. A cryopreservation protocol, using a mixture of 30% glycerol and 70% concentrated P. persalinus cell culture, incorporating rate-controlled freezing at −80 °C before liquid nitrogen storage, maintained a high recovery efficiency after 8 wk of storage. These results suggest that broader application of this protocol to build a cryopreserved marine protozoa culture bank for biological studies may be possible.