Practice and prospects of microbial preservation

A growing interest in culturable diversity has required microbiologists to think seriously about microbial preservation. In addition to the isolation and cultivation of pure strains, adequate preservation without changes in morphological, physiological and genetic traits is necessary. This review consolidates different methods used for preservation of microorganisms with an emphasis on cryopreservation and lyophilization. The critical points of cryopreservation and lyophilization are highlighted to explain how several extrinsic and intrinsic factors affect the cell survival and recovery during the process of long-term preservation. Factors responsible for alteration in genotypic and phenotypic integrity of cultures during preservation and methods used for their evaluation have been incorporated. We emphasize the importance of depositories and highlight their current funding status. Future areas for preservation research, including cell dormancy, ecosystem and community level preservation and the effects of the viable but non-culturable state on post-preservation recovery of the cells are also discussed.