The cryopreservation of Chlamydomonas

A cryophilic strain of the unicellular green alga Chlamydomonas, C. nivalis was found to be more resistant to the stresses both of freezing and thawing and of shrinkage and rehydration than was a mesophilic strain C. reinhardii. C. nivalis was found to have a higher degree of unsaturation of phospholipid fatty acids. Following freezing and thawing of C. reinhardii there was a direct correlation between reduction in cell viability and loss of membrane selective permeability. Activation of intracellular phospholipases occurred at an early stage of freezing injury. Attempts to cold harden C. reinhardii were unsuccessful. For C. reinhardii methanol was the only effective cryoprotectant for freezing to and thawing from −196 °C and the effects of cooling rate upon cellular survival are presented.