Figure 1.

(A) Photographs of the cotton swabs obtained after sampling the bacterial samples (50 µL) containing E. coli O157: H7 (OD₆₀₀ = ~1) and S. aureus (OD₆₀₀ = ~1), after reacting with the reagent (50 µL) containing TMB (1.25 mM) and H₂O₂ (11.2 mM) at pH 3 for 25 min. (B) UV-Vis absorption spectra of the bacterial samples (0.2 mL) including E. coli O157: H7 (OD₆₀₀ = 1) and S. aureus (OD₆₀₀ = 1) obtained after reaction with TMB and hydrogen peroxide (11.2 mM) at pH 3 for 25 min, followed by the reaction with additional hydrogen peroxide (7.2 M, 5 µL) for another 5 min. The inset shows the photographs of the resultant samples. Representative microscopic images of E. coli O157: H7 (C) without and (D) with the addition of H₂O₂ (11.2 mM, 2 µL) at pH 3. The bacterial samples were stained with methylene blue (1 mM, 2 µL) for 2 min before investigation by the optical microscope. (E,F) Corresponding TEM images of the samples shown in panels (C,D).