The effect of bactericides on bacteria was studied using an electrochemical method for measuring the glucose-oxidizing activity of bacterial whole cells. When
Esherichia coli IFO3301 (
E. coli) and
Lactobacillus plantarum IFO14711 (
L. plantarum) were exposed to ethanol, hydrogen peroxide, or hypochlorous acid, the glucose-oxidizing activity and the colony formation decreased with increasing bactericide concentration. The glucose-oxidizing activity of both
E. coli and
L. plantarum was more sensitive to bactericides than the colony formation. In contrast with the case of
E. coli and
L. plantarum, the glucose-oxidizing activity of
Pseudomonas putida IFO14164 (
P. putida) was resistant to bactericides. Exposure of
P. putida cells to 26% ethanol or 0.5% hydrogen peroxide at 30°C for 10 min caused a loss of colony formation, while the glucose-oxidizing activity remained at approximately 20%, even after exposure to 95% ethanol or 3% hydrogen peroxide. In
P. putida and
E. coli, the colony formation and the glucose-oxidizing activity of cells grown to log the phase were more sensitive to hypochlorous acid than those of the cells grown to the stationary phase. When
P. putida cells were exposed to a low concentration of hypochlorous acid, the bactericide-resistance of the colony formation increased, but the resistance of the glucose-oxidizing activity decreased. In the case of
E. coli, the pretreatment with hypochlorous acid enhanced the bactericide-resistance of both the colony formation and the glucose-oxidizing activity.
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