Evaluation of Preservation Techniques of Microorganism Resources in the MAFF Genebank

Abstract

In the central bank of the microorganisms section in the Ministry of Agriculture, Forestry and Fisheries (MAFF) Genebank in Tsukuba, 14,836 strains of fungi, bacteria, yeasts and others are preserved by various methods including cryopreservation and freeze-drying. To evaluate preservation techniques for these microorganisms, the viability of the preserved microorganisms was examined at regular intervals. Almost all tested strains, except for 5 strains out of 2,334 strains, of yeasts, bacteria and Actinomycetes were preserved well in freeze-dried form, indicating that freeze-drying is suitable for their preservation. As for fungi and Oomycetes, 6,578 strains out of 6,681 tested strains (98.5%) and 264 (63.8%) of 414, respectively, survived one-year preservation in the vapor phase of liquid nitrogen. The details on survival of the preserved fungal strains were as follows: 99.0% (1,107 strains/1,118 tested strains) survival in Ascomycota, 96.1% (1,552/1,615) in Basidiomycota, 98.6% (73/74) in Zygomycota, and 99.3% (3,846/3,874) in anamorphic fungi. Thus, cryopreservation is excellent for preservation of most fungus strains, but is not suitable for preservation of many Oomycetous strains.