Cryopreservation of the Model Alga Ectocarpus (Phaeophyceae)

The brown alga Ectocarpus has recently become the first fully sequenced multicellular alga and is an important biological model. Due to the large and growing number of Ectocarpus strains isolated and maintained by the research community, including increasing numbers of mutants, there is an urgent need for developing reliable, cost-effective long-term maintenance techniques. We report here that cryopreservation constitutes an attractive option in this respect, using a simple two-step protocol employing combined DMSO 10% (v/v) and sorbitol 9% (w/v) as cryoprotectants. This model organism appears to be remarkably robust and post-cryo recovery has been observed in all strains tested in this study. Cultures can be regenerated by the germination of cryopreserved zooids (spores), or the recovery of vegetative cells. In the latter case, dividing surviving cells may grow into the cell lumen of a neighbouring dead cell, eventually regenerating a phenotypically normal thalloidal structure.