An investigation was made of the various factors affecting survival during storage of Serratia marcescens strain 8 UK after freeze-drying by a continuous vacuum sublimation method. Rtogers (1914), Heller (1941), Fry and Greaves (1951), and Proom and Hemmons (1949) reported on environmental conditions affecting the storage survival of various types of bacteria; Naylor and Smith (1946) made a similar study of S. marcescens. Fry (1954) summarized the factors affecting survival as: 1. Nature of the organism. 2. Suspending medium. 3. Conditions of growth and age of culture. 4. Cell concentration of the suspension. 5. Degree of vacuum and drying temperature. 6. Atmosphere of storage. 7. Temperature of storage. 8. Residual moisture content. However, Fry does not distinguish between those factors affecting survival during drying aind those affecting survival during storage. Our objective was to determine as accurately as possible those conditions most favorable to the storage survival of a strain of S. marcescens. The variables investigated were: residual moisture content, age of culture, control of pH during growth of the organism, concentration of cell suspension, atmosphere of storage, storage of whole pellets vs. ground powder, additioni of glucose to the medium at the end of the usual sugarutilization cycle, and temperature of storage. MATERIALS AND MIETHODS The organisms used in our investigation.s wvere propagated by methods described by Benedict et al. (1957) on a medium consisting of an aqueous mixture of 5 per cent dried skim milk solids, 3 per cent Wilson's protopeptone no. 343,5 and 2.2 per cent glucose (mono-1 This work was supported by a contract with the Chemical Corps,

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