652 Table Gene Banks Collections Maintaining Microorganisms Collection Location Number of strains Type of material Agricultural Research Service Culture Collection, USDA American Type Culture Collection (ATCC) Peoria, IL (US) 78,010 Algae, bacteria, fungi, yeasts, actiomycetes Rockville, MA (US) 53,615 CABI Bioscience UK Centre (formerly (IMI) Centraalbureau voor Schimmelcultures (CBS) Culture Collection, University of Goteborg (CCUG) Egham, UK Baarn, The Netherlands 21,000 41,300 Algae, bacteria, fungi, yeasts, protozoa, cell lines, hybridomas, viruses, vectors, plasmids, phages Fungi, bacteria, yeasts Fungi, yeasts, lichens, plasmids Goteborg, Sweden 28,100 Bacteria, fungi, yeasts spermatozoa The testicular cells were frozen-thawed prior to transplantation and development, and thus there may be some merit in exploring the cryopreservation of testicular cell suspensions as an alternative or adjunct to the preservation of spermatozoa Cell suspension from genetically important animals could be used to populate the testes of common species, thus permitting the eventual harvesting of spermatozoa It should be stressed that this technique is still only in its infancy Unlike animal species in which reproductive cells and tissues are stored to conserve the gene pool, in humans they are stored for the use of the couple/woman electing to have them cryopreserved Some embryos are subsequently donated for the treatment of others Storage is limited by law in some countries The storage of embryos is common practice in in vitro fertilization (IVF) clinics worldwide, with about 70 offering the service in the United Kingdom alone Oocyte cryopreservation is poorly developed and few clinics store them other than for research An increasing number are offering tissue storage Despite sporadic reports of cryopreservation using nonequilibrium rate cooling, the vast majority of clinics prefer conventional slow cooling rate procedures with the samples loaded into ‘‘straws’’ (embryos and oocytes) or plastic vials (ovary) The first step involves the addition of the cryoprotectant (about 1.5 M; 1–2 propanediol sucrose (pronucleate and early cleavage stage embryos), dimethyl sulfoxide (4–8 cell embryos, and ovary) or glycerol (blastocyst stage embryos)) Ice formation is then induced at À to À 1C and the samples are cooled further at rates of about 0.3 to 0.5 1C per minute to various subzero temperatures before storage in liquid nitrogen After warming at appropriate rates (of about 20 to more than 300 1C per minute), the samples are returned to isotonic conditions stepwise, with or without the addition of sucrose to the diluent Microorganisms The most widely applicable preservation method for the preservation of microorganisms that retains viability and stability is cryopreservation However, for convenience and ease of transport freeze-drying is preferred for most bacteria, viruses, and sporulating fungi (see Hunter-Cevera and Belt, 1996) There are currently 497 collections from 60 countries maintaining microorganisms registered with the World Data Centre for Microorganisms in Japan (see Sugawara and Miyazaki, 1999) Their on-line database lists species held and the expertise and services provided by the collections along with contact addresses and links to collection websites There are about 11,500 species held Over 25% of the strains are held by of the 497 collections (see Table 1) DNA Banks DNA banks have been established in several places worldwide (Adams, 1997), the largest (more than 140,000 clones) being for plant and animal material at the NIAR in Japan This collection is mainly constituted of rice clones (about 36,000 comprising Random Fragment Length Polymorphisms, cDNA, YAC) and pig clones (about 106,000 comprising cosmids, BAC, cDNA) The most diverse DNA bank for plants is at the Royal Botanic Gardens (RBG) Kew, which currently holds more than 10,000 DNA samples from a wide range of species Standards of quality of preservation differ between banks and some, such as those at the Missouri Botanical Gardens (St Louis, Missouri, in the United States) and several zoos, store only frozen tissue Others extract DNA and purify it to varying degrees Purposes for these banks differ as well, with some established to hold samples of a particular country or region with the intent of using these in conservation genetic studies, whereas others focus more on taxonomic and systematic studies, such as that at RBG Kew Most banks are prepared to consider sharing aliquots of DNA or small samples of tissue with researchers at other institutions Field Gene Banks Field gene banks are ex situ collections of mainly agricultural or forest species They should be contrasted with what might be termed ‘‘farm gene banks’’ where crop germplasm is, in effect, conserved in situ by the farmer Field gene banks normally comprise considerably more individuals per accession than is the case in botanic gardens Their particular use is for the conservation and utilization of species with the following traits: • • • Have nonbankable seeds Have long life cycles where growing up material for regular study from a seed collection is impractical Are normally vegetatively propagated