Escherichia coli cultures in the logarithmic phase or resting were treated with various concentrations of ozone in saline solution. Approximately 2 X 107 molecules of ozone per bacterium killed 50% of the cells. Ozone caused leakage of cell content into the medium, and lysis of some cells. Low concentrations of ozone did not react with the glutathione within the cells, although reaction with glutathione in solution was immediate and stoichiometric. The effect on nucleic acid within the cells was to change the solubility and to cause the release of ultraviolet-absorbing material into the medium. Ozone attacked the ring structure of the base or the carbohydrate only when the substance was in the medium. Nucleic acids released into the medium were reabsorbed by cells which were not lysed. Viable cells resumed growth immediately, and grew at rates determined by the nutrients either added to the medium or which resulted from leakage and lysis of nonviable cells. It is postulated that the primary attack of ozone was on the cell wall or membrane of the bacteria, probably by reaction with the double bonds of lipids, and that leakage or lysis of the cells depended on the extent of that reaction.

SUMMARYHexokinase was determined in extracts of Escherichia coli by measurement of the reduction of nicotinamide-adenine dinucleotide phosphate by glucose-6-phosphate dehydrogenase, and the glucose-6-phosphate formed by the action of hexokinase. This method gave reproducible results. Extracts of E. coli contained low hexokinase activity when the organism had been grown in the absence of glucose and this enzyme activity was increased after adaptation of the organism to growth on glucose. The E. coli needed 2-2.5 divisions to reach the degree of hexokinase activity of glucose-grown bacteria when transferred to salts + glucose from media not containing glucose.

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