I just learned that Invitrogen has a cryopreservation kit to store Chlamydomonas and other algae at -80°C (thanks Emily):
The GeneArt® Cryopreservation Kit for Algae is used to preserve algal strains and clones for storage at -80°C for years, thus eliminating liquid nitrogen storage and continuous cultures as a way to maintain your clones. Cryopreservation is the optimal choice for preservation and long-term storage of algae, since it minimizes genetic drift, facilitates strain and clone exchange between labs, and helps reduce maintenance labor and costs. Simply grow your cells in the presence of Cryopreservation Reagent A for 2–5 days, harvest, resuspend in Cryopreservation Reagent B, and freeze a small aliquot in one of two recommended freezing containers* at -80°C. The GeneArt® Cryopreservation Kit for Algae has been used to preserve Chlamydomonas and Chlorella strains with 100% resuscitation after thawing.
Maybe if I had gone to Chlamy 2014 I would have already known that. Cryopreservation has previously been difficult for Chlamydomonas researchers, requiring storage in liquid nitrogen. Having looked through the protocol, it doesn’t look too onerous. Essentially, you grow the algae for three days in TAP mixed with one cryopreservation agent, centrifuge and resuspend the cells in the second cryopreservation agent, incubate at room temperature for 30-45 minutes, and freeze in a cryo container.
I assume that “100% resuscitation after thawing” means that 100% of the cultures recover. It can’t mean that 100% of cells survive, right?
Has anyone tried this with colonial/multicellular algae?