212 • Technologies To Maintain Biological Diversity 



certain microbial cells, low-temperature freez- 

 ing is inexpensive and useful for a short period. 

 Like immersion in mineral oil, however, repeti- 

 tive recovery, authentication, and restorage 

 make this technique too labor-intensive for long- 

 term maintenance of micro-organisms. 



The majority of microbial cells die if they are 

 dried at ambient temperatures (16). But a few 

 can withstand dehydration and remain viable 

 for moderate periods of time. Spore-forming 

 bacteria are particularly suited to this method 

 of storage. Microbial cells are usually trans- 

 ferred to a sterile, solid material, and then de- 



hydrated under vacuum. A soil, paper, or ce- 

 ramic bead medium is frequently used. Cells 

 also may be suspended in gelatin solution and 

 then drops of the gelatin dried under vacuum. 

 Once dehydrated, the cells must be stored in 

 desiccators but will remain viable longer if 

 refrigerated. Recovery of the cells is by rehydra- I 

 tion with nutrient medium and subculture. This 

 method is relatively inexpensive and routinely 

 used for some important bacterial genera (e.g., | 

 Rhizobium). However, other techniques, if 

 available, are preferred for long-term storage 

 (19). 1 



NEEDS AND OPPORTUNITIES 



No major technical constraints limit the stor- 

 age and use of micro-organisms in the United 

 States and most other industrial nations, al- 

 though developing countries lag behind in the 

 application, use, and technological knowledge 

 of micro-organisms (28). The most satisfactory 

 long-term storage techniques for micro-orga- 

 nisms are also those that are technologically 

 the most sophisticated. In the case of cryogenic 

 storage, the technique requires a dependable 

 source of liquid nitrogen. Lyophilization of cul- 

 tures in sealed, evacuated glass-ampules cre- 

 ates culture units with excellent longevity, even 

 when stored at room temperature. The attrac- 

 tion of this method for developing countries 

 is diminished slightly by the relatively high ini- 

 tial cost of equipment and problems keeping 

 such equipment operational (19). 



Improvisation in the laboratories of develop- 

 ing-country scientists has resulted in a wide ar- 

 ray of variations of standard preservation meth- 

 ods (19). These modified methods are, in many 

 cases, satisfactory to the individual collection 

 curators, though most require micro-organisms 

 to be regularly subcultured. This requirement 

 makes these methods suitable only for relatively 

 small collections, and it increases the likelihood 

 of strains becoming genetically adapted to cul- 

 ture and losing their original characteristics. 



Catalog Collections 



Maintaining and distributing a current cata- 

 log is the goal of virtually every collection cu- 

 rator. Without such a compilation to provide 

 potential users with ready access to its contents, 

 the value of a collection is greatly diminished. 

 That very few collections are adequately cata- 

 loged is a reflection of just how onerous this 

 task can be. In a sense, this aspect of collec- 

 tion management has been constrained by lack 

 of an appropriate technology (19). The advent 

 of microcomputers and highly adaptable, user- I 

 friendly database management systems soft- ' 

 ware heralds a new era enabling a curator to 

 compile, print, and update a catalog inexpen- || 

 sively and with relative ease (9). Such electronic 

 catalogs would make current collections more 

 accessible and improve their management (4). 



One way to catalog the contents of various 

 collections is through creation of a National 

 Microbial Resource Network. Two main obsta- 

 cles can be anticipated to such a network: | 



1. the differences in history, traditions, and 

 independence of existing collections; and 



2. the difficulty of standardizing technical 

 and informational protocols to assure mean- j| 

 ingful interchange of germplasm and data ' 

 among participating network institutions. 



