Journal of Miuobiological Methods,16 (1992) 281-287 @ 1992 Elsevier Science Publishers B.V. All dghts reserved 0167 - 7012192l$05.00 MIMET 00536 Long-term preservation of halophilic archaeb acterta and thermoacidophilic archaeb acterta by liquid drying ' T. Sakane', I. Fukudab, T. Itohb and A. Yokotau alnstitute for Fermentation, Osaka, 17-35, Juso-honmachi 2-chome, Yodogawa-ku, Osaka 532, Japan; bColl"g, of Liberal Arts and Science, Kitasato (lniversity, t5 l, Kitasato l-chome, Sagamihara 228, Japan (Received 2 January 1992; revision received 2 JluJy 1992; accepted 5 July 1992) Summary A liquid drying (L-drying) method was applied satisfactorily to the long-term preservation ofextremely halophilic archaebacteria and thermoacidophilic archaebacteria that are sensitive to freezing and freeze- drying. Survival values of Halobacterium, Haloferax, Haloarcula, Halococcus, Natronobacterium, Thermoplasma, Sulfolobus and Acidinnus were more than 5o/o after drying and more than 0.0402 alter being stored at 37'C for 2 weeks. The survival values of these dried specimens after long-term preservation at 5'C corresponded to those estimated from the results of the accelerated storage test. Therefore, it is considered that the accelerated storage test is useful for estimating the stability of the dried specimens of archaebacteria during preservation and that the dried specimens of even the most fragile bacterium, Thermoplasma, will remain viable for more than 15 years when they are kept at 5'C. Key words: Halophilic archaebacteria; Liquid drying; Long-term preservation of archaebacteria Introduction Liquid drying (L-drying), which involves vacuum-drying of samples from the liquid state without freezing, is known to be useful for the long-term preservation of microorganisms [-3], especially those microorganisms sensitive to freezing or freeze-drying [4-6]. At the Institute for Fermentation, Osaka (IFO), this method has been used for preserving various kinds of bacteria, bacteriophages, yeasts and fungi, and it is expected that it might be possible to preserve almost all the strains in IFO, except for zoosporic fungi and sterile strains of other groups of fungi, semipermanently [7- l0l. Correspondence to: T. Sakane, Institute for Fermentation, Osaka (IFO) 1 7-85, Juso-honmachi 2-chome, Yodogawaku, Osaka 532, Japan. 281