|Titre||Cryopreservation of the coccolithophore, Emiliania huxleyi (Haptophyta, Prymnesiophyceae)|
|Type de publication||Journal Article|
|Year of Publication||2005|
|Auteurs||Houdan, A, Véron, B, Claquin, P, Lefebvre, S, Poncet, J-M|
|Journal||Journal of Applied Phycology|
We studied the cryopreservation of the most common coccolithophore, Emiliania huxleyi which is considered as one of the main global carbon cycle participants. Both stages of this complex life cycle species were submitted to gradual addition of three distinct cryoprotectants: dimethylsulfoxide (7.5% v/v), methanol (5% v/v) and proline (0.5 M). They were then control-rate cooled (-5 °C min-1) to -50 °C before plunging into liquid nitrogen. Free radical oxygen species have been proposed to occur in cells subjected to pre-freezing manipulation or to cooling. Therefore, catalase (preventing accumulation of hydroxyl radicals) was evaluated for its ability to improve cell viability before and after freezing-thawing challenge. With the exception of proline which induced a decrease in diploid cell proliferation, cryoprotectants had no deleterious effects. On the contrary, growth of the haploid stage was enhanced by each CPA treatment, suggesting mixotrophic growth. Cryopreservation succeeded when dimethylsulfoxide was used, and the late exponential phase was obtained as soon as the 15th post-thawing day. Cell densities were then similar to the unfrozen controls. Catalase had no beneficial effect on the ability of cells to grow, neither prior freezing nor after thawing. In comparison with former attempts to cryopreserve E. huxleyi in other culture collection centers, our protocols allowed faster recovery.