Improvement of the L-drying procedure to keep anaerobic conditions for long-term preservation of methanogens in a culture collection
2006 Volume 22 Issue 2 Pages 99-104
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2006 Volume 22 Issue 2 Pages 99-104
The L-drying (liquid-drying) method is currently one of the well-known methods for preserving microorganisms. We have optimized the method to make it applicable for the preservation of methanogens, a group of strict anaerobic archaea, by keeping anaerobic conditions in all procedures without using an anaerobic chamber. Three strains of methanogens, namely, Methanobrevibacter arboriphilus NBRC 101200, Methanothermobacter thermautotrophicus NBRC 100330T (T, type strain), and Methanoculleus chikugoensis NBRC 101202T, were preserved stably by the L-drying method optimized in the present study, and recovered well even after an accelerated storage test at 37℃ for 2 weeks, which approximately corresponds to the normal storage at 4℃ for 20 years. The number of viable cells of these strains after L-drying was found to be between 104 and 106 cells/ml against 105 through 106 cells/ml of the original suspension. On the other hand, cells of Methanosarcina mazei NBRC 101201 grown on acetate were viable only when they were harvested before the stationary phase of growth. It was revealed that attention should be paid to the growth phase of the culture used for preservation. The L-drying method improved in this study is thus expected to be applicable for long-term preservation of various methanogens that can then be easily transported by postal or parcel delivery to other laboratories..
