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ABSTRACT: The microorganisms Escherichia coli DH5 alpha and Bacillus thuringiensis HD-1 show an increased tolerance to freeze-drying when dried in the presence of the disaccharides trehalose and sucrose. When the bacteria were dried with 100 mM trehalose, 70% of the E. coli and 57% of the B. thuringiensis organisms survived, compared with 56 and 44%, respectively, when they were dried with sucrose. Only 8% of the E. coli and 14% of the B. thuringiensis organisms survived drying without the sugars. Fourier transform infrared spectroscopy was used to investigate the role of membrane phase transitions in the survival of the organisms during drying and rehydration. Both E. coli and B. thuringiensis showed an increase of 30 to 40 degrees C in the temperature of their phospholipid phase transition when dried without the sugars, while phase transition temperatures of those dried with the sugars remained near those of the hydrated cells. A Fourier transform infrared spectroscopy microscope made it possible to investigate the effects of drying on the protein structure in the intact cells. The amide II peak shifts from 1,543 cm-1 in the hydrated cells to about 1,533 cm-1 in the cells dried without sugar. There is no shift in the amide II peak when the cells are dried with trehalose or sucrose. We attribute the increased survival to the sugars' ability to lower the membrane phase transition temperature and to protect protein structure in the dry state.(ABSTRACT TRUNCATED AT 250 WORDS)
Applied and Environmental Microbiology 11/1995; 61(10):3592-7. · 3.83 Impact Factor
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ABSTRACT: Freeze-dried cultures of wild-type and genetically engineered strains of Escherichia coli lost their colony-forming ability upon exposure to air, visible light, and certain relative humidity levels. Both strains could be maximally protected from these lethal effects with 100 mM trehalose, a concentration calculated to just saturate the interphospholipid spaces in the cell membrane, thus preserving the liquid-crystalline structure. The trehalose protection was observed for at least 96 h. Trehalose increased viability as much as 2000-4000% over nontreated populations. In all cases, exposure to environmental conditions was more damaging to the genetically engineered strain.
Cryobiology 11/1993; 30(5):519-23. · 2.06 Impact Factor
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ABSTRACT: Because the death mechanisms of freeze-dried and air-dried bacteria are thought to be similar, freeze-drying was used to investigate the survival differences between potentially airborne genetically engineered microorganisms and their wild types. To this end, engineered strains of Escherichia coli and Pseudomonas syringae were freeze-dried and exposed to air, visible light, or both. The death rates of all engineered strains were significantly higher than those of their parental strains. Light and air exposure were found to increase the death rates of all strains. Application of death rate models to freeze-dried engineered bacteria to be released into the environment is discussed.
Applied and Environmental Microbiology 03/1993; 59(2):594-8. · 3.83 Impact Factor
