5.4. Medium for long-term storage

Freezing is an effective long-term storage of M. plutonius as well as other bacterial isolates. Broth cultures are mixed with chemicals such as glycerol or DMSO to limit damage upon freezing. It is possible to use proprietary cryopreservation kits which can even specialize in the preservation of anaerobic organisms (e.g. PROTECT system from Thermo Fisher Scientific). Using such proprietary kits, pure cultures of M. plutonius are added to a tube containing cryopreservation liquid and ceramic beads. After temperature controlled freezing, cultures can be recovered by removing a single ceramic bead and plating directly onto selective media. Results to date indicate 100 % successful recovery after 6 months storage at -80°C (Budge, unpublished data).