Q: I am working on the diatoms cultures that we obtained from your culture collection. You mentioned that these cultures were cryopreserved before we received them. On the Bigelow homepage I found some information about the cryopreservation procedure, but not a detailed protocol. Is there such a protocol that you could share with us? We would especially like to know how dense cultures should be for cryopreservation as well as which survival rates one can expect.
A: We try to cryo strains when they reach mid log so every culture is different. We run a control with every cryo event of three tubes. These are pulled 24 hours after the event has been placed in vapor LN2. Only if all three tubes establish viable biomass is the cryo run deemed successful. Once the culture has reached mid log it is mixed with the cryoprotective agent(CPA), DMSO is this case. The percentage and grow back time is listed for the strains you ordered on the webpage under the "Cryopreservation" tab. A minimum of fifteen minutes in the CPA before we aliquot 1mL into cryo tubes. These are then placed in a "Mr Frosty" and stored at -80 for at least three hours. The cryo tubes are then placed in LN2 vapor for long term storage.