ABSTRACT
This chapter indicates how people may obtain information about collections from which cultures can be ordered for their use. Those who are routinely using the same organism(s) for experimental work must maintain their organism(s) by subculturing, namely the periodic transfer to fresh media. It is frequently suggested that minimal medium be used for subculturing, in order to prolong the time between transfers. Reliable long-term methods are required by culture collections. The procedures used in collections to maintain cultures are designed to maintain a culture in a stable condition. Freeze-drying is a very successful method which involves the removal of water from a microbial culture by sublimation under reduced pressure. Success depends on the prevention of damage by the process of freezing and as a result of oxidation. With regard to freezing, if micro-organisms are frozen, no further metabolism occurs when all the internal water is frozen. However, ice recrystallization can occur above—130°C and this can damage the frozen organism.
