Survival and growth initiation of defrosted Escherichia coli as affected by frozen storage menstrua.

Generally speaking, the literature indicates that the number of bacteria surviving subfreezing temperatures will be functions of: (1) initial numbers of viable cells present when frozen (Record and Taylor, 1953; Kropp, 1950), (2) the rate of the freezing and thawing process (Luyet and Gehenio, 1940), (3) the temperature of storage, with 0 to -20 C being more destructive than the range below -20 C (Hilliard and Davis, 1918; Haines, 1937-38), (4) the time or duration of the storage period (Weiser and Osterud, 1945), and (5) the physical protection offered by the menstrua in which the microorganisms are frozen. The object of this investigation was to determine the effects of various additives and suspending fluids on both the survival and the growth initiation abilities of Escherichia coli which had been sharp frozen and then stored at -9 C. The use of glycerin as a protective agent against the effects of freezing and thawing has been of interest since Keith (1913) first showed that a large percentage of "B. coli" remained viable after six months of storage in the frozen state. Smith et al. (1951) studied the formation and dissolution of ice crystals in the presence of glycerin. They observed that channels and spaces formed into which cells (fowl spermatozoa, rabbit red blood cells, and ameba) could lodge and thus escape the effects of ice crystallization. Luyet and Gehenio (1952) concluded that the protective action of glycerol against freezing injury depended on its penetration into the tissues, relatively low toxicity at subfreezing temperatures, and a low eutectic point. Lovelock (1953) believed that glycerol exerted its full protective action against hemolysis of red blood cells from freezing and thawing only when present within and without the cell. Hollander and Nell (1954) theorized that the protection offered by glycerol against the effects of freezing could be explained by its physical characteristics, when in solution. They believed that the death which occurred during freezing and thawing resulted from mechanical compression on the microorganisms.