Inactivation of Escherichia coli by O⁻ water

To clarify the effects of O⁻ (atomic oxygen radical anion) water on the viability and morphological alteration of Escherichia coli. O⁻ water (OW) was prepared by bubbling of O⁻/argon (Ar) flux into deionized water. O⁻ and hydrogen peroxide (H₂O₂) in the resultant OW were analysed by electron paramagnetic resonance and ultraviolet (UV) absorption spectroscopy. The population of E. coli treated by a typical OW of pH 4·30 ± 0·20 [(2·5 ± 0·8) x 10⁻³ mmol l⁻¹ O⁻; 0·5 ± 0·2 mmol l⁻¹ H₂O₂) was reduced by more than 3 log CFU ml⁻¹ within 60 min at 30°C. Through scanning electron microscopy observation, the OW-treated cells appeared dramatically collapsed. The release of nucleic acid induced by OW was identified by UV absorption spectroscopy. O⁻ water can result in inactivation of E. coli, nucleic acid release and cellular damage under the controlled laboratory conditions in excess of 15-30 min. Reactive oxygen species may play an important role in the inactivation process. This study first revealed that OW could inactivate E. coli, which may be potentially useful in developing a novel approach for the microbial decontamination of food, water or heat-sensitive material.