Variants of Serratia marcescens induced by freeze-drying

Outermost-cell-surface changes in an encapsulated strain of Staphylococcus aureus after preservation by freeze-drying

The effects of drying time during freeze-drying on the outermost cell surface of an encapsulated strain of Staphylococcus aureus S-7 (Smith, diffuse) were investigated, with special attention paid to capsule and slime production. To quantify capsule and slime production, capsule antigen production and cellular characteristics such as growth type in serum-soft agar, cell volume index, and clumping factor reaction were examined. After freeze-drying the colonial morphology of strain S-7 was altered from a diffuse to a compact type in serum-soft agar. In accordance with these changes, the titer of the clumping factor reaction increased while the cell volume index, capsule and slime production, and capsule antigen production were markedly decreased in parallel with the period of freeze-drying. The ability of the strain to adhere to collagen, fibrinogen, and soybean lectin was also compared before and after freeze-drying. Fibrinogen levels slightly increased when 10% skim milk and 2% honey were used as cryoprotective agents and showed a remarkable increase when 0.05 M phosphate buffer was used as a control. Also, the ability of strain S-7 to adhere to soybean lectin declined, whereas no changes were observed for collagen under any conditions. Strain S-7 was phage nontypable before freeze-drying but the number of typable cells increased after freeze-drying; phage-typable cells reacted to phage 52 alone after 5 h of freeze-drying, but additional cells also proved to be phage typable to phage 42E after 10 h. Electron micrographs indicated that strain S-7, an encapsulated strain, was converted to an unencapsulated state after freeze-drying.(ABSTRACT TRUNCATED AT 250 WORDS)

Limits to life at low temperatures and at reduced water contents and water activities

Liquid water is generally considered an absolute requisite for functional life; consequently, life is expected to function only over the range of temperatures that permit its existence. These limits, however, do not apply to cell survival. Some cells can survive the closest attainable approach to 0 K, and some can survive the loss of over 99% of their water.

Deoxyribonucleic acid strand breaks during freeze-drying and their repair in Escherichia coli

Freeze-drying of Escherichia coli cells caused strand breaks of deoxyribonucleic acid (DNA) in both radiation-sensitive and -resistant strains. However, in the radiation-resistant strain E. coli B/r the damaged DNA was repaired after rehydration, whereas in the radiation-sensitive strain E. coli Bs-1 the damaged DNA was not repaired and the DNA was degraded. Repeated freeze-drying did not break the damaged DNA into smaller pieces.