Maintenance of cultures
- Metabolically active cultures
Microalgal strains of SAG are primarily maintained by routine serial sub-culturing under controlled environmental conditions. The cultures are transferred at the late log/stationary phase to fresh, sterile medium.
This leads to metabolically active cultures that can be used at short notice. The objective is to retain a healthy, physiologically, morphologically and genetically representative specimen. A key factor to be considered is that different ages of subcultures may provide different stages of the life cycle.
Routine serial sub-culturing is a labour- and consumable-intensive process and certainly limits the capacity of workers to maintain large numbers of strains.
A successful alternative approach for the ex situ conservation of algal and cyanobacterial cultures is cryopreservation.
With the help of a Europe-wide research project, COBRA, cryopreservation of microalgae has been established at the SAG. Since then 30% of all the SAG's holdings of terrestrial microalgae are kept in cryopreservation. This means a great step forward in the quality of the SAG cultures because cryopreservation ensures physiologically and genetically stable cultures.