Preservation of Microorganisms by Freeze-Drying

Abstract

Inasmuch as all living things usually require a high content of water either internally or externally, or both, it is remarkable that microorganisms, especially spore forms, can sometimes withstand an extreme desiccating environment. Any success achieved by chemical or physical means in modifying viability, that is in hastening or preventing death of the desiccated cell, has implications in many different fields. The various techniques exploited during the last 45 years in the preservation of bacteria by drying have been reviewed in an interesting and very useful manner by Fry (1954). Although he commends Naylor and Smith (1946) on the logical development of their stabilizing medium for the freezedrying of Serratia marcescens, he points out that its general applicability would have to be tested with more sensitive organisms. The present study of preservation by drying is also limited to S. marcescens but a considerable variety of new substances has been tried besides the Naylor-Smith components. Some of our results should find application in the preservation of other organisms freeze-dried under similar conditions. Experiments with sensitive strains of yeast and bacteria will be reported in a later paper.