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LABORATORY PROCEDURES FOR MICROORGANISMS

REFERENCE NO.: M/1998/3.01


TITLE: STORAGE OF PRESERVED MICROORGANISMS


Service collections may house a large number of strains that are hardly distributed. In such cases collections cannot afford to follow the practice of a large master stock, from which many subsequent distribution stocks can be derived. The nature of the strains is also a major factor in the decision whether such a procedure is necessary. Unicellular microorganisms have more chances of selection than filamentous microorganisms, and sporulating filamentous microorganisms more than non-sporulating ones. Collections have to estimate the risks, and then decide what procedure to follow for a particular strain or groups of strains.

SECURITY MEASURES

It is essential, that material from the first preservation batch remains available as long as possible. The protocols to achieve this vary with the expected turnover.

To minimize the probability of strains being lost, each strain should be maintained - if possible - by at least two different techniques. One of these should be cryopreservation of lyophilization (as recommended by the WFCC guidelines, see M/1999/1.00 Appendix 1). For most microorganisms, storage in liquid nitrogen is the optimal method for minimizing the risk of genetic change.

To minimize the risks to important genetic resources from fire, flooding, earthquakes, etc. collections should arrange to have duplicates of at least the most important and irreplaceable strains securely housed in a different building or ideally at a separate site.

Accessibility to stock must be restricted.

STORAGE CONDITIONS

For freeze-drying the stability of the product is dependent on several parameters: the residual moisture content of the product, the physical properties of the lyoprotectant and the storage temperature. After successful preservation (freeze-)dried cultures are stored at 10"C or below.

For freezing the storage temperature is determined by the applied method. Frozen cultures are stored in or above liquid nitrogen or at ãpprox -70"C.


Guidelines prepared for CABRI by DSMZ, CBS and BCCM, 17 May 1998, updated August 1999
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Copyright CABRI, 1998

 

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