title: Deoxyribonucleic acid strand breaks during drying of Escherichia coli on a hydorohobic filter membrane.
abstract: Cells of Escherichia coli mounted on a hydrophobic filter membrane were dried under various vapor pressures. A mutant defective in deoxyribonucleic acid repair (uvrA recA) was more sensitive to drying at a water activity of 0.53 or below than the parent strain but not at a water activity of 0.75 and above. Sucrose gradient studies showed that single- and double-strand breaks of deoxyribonucleic acid occurred at a water activity of 0.53 or below, but no breaks could be observed at a water activity of 0.75 or above. These results were observed in all cells rehydrated with 0.03 M tris (hydroxymethyl) aminomethane-hydrocholoride buffer solution at 0 or 37 degrees C, in the presence or absence of oxygen, with saturated water vapor or with a hypertonic solution followed by a gradual dilution. Freezable water was detected in the cells only at a water activity above 0.75 by differential scanning calorimetry. Removal of unfreezable water of cells in the drying, therfore, might induce deoxyribonucleic acid strand breaks.
mesh_terms: D004260:DNA Repair; D004269:DNA, Bacterial / Q000032:analysis; D003890:Desiccation; D004926:Escherichia coli / Q000032:analysis / Q000235:genetics / Q000502:physiology*; D008851:Micropore Filters; D009154:Mutation; D009691:Nucleic Acid Denaturation; D014867:Water
chemical_list: D004269:DNA, Bacterial; D014867:Water