Fig. 1.

Analysis of Raman spectra and DIC and SYTO 16 fluorescence images of a B. cereus spore during wet-heat treatment. (A) Raman spectra and DIC and fluorescence images of a B. cereus spore during wet-heat treatment. The B. cereus spore was incubated in water at 80°C as described in Materials and Methods, and the Raman spectra (curves a to d) and images (from top to bottom) were recorded at 2.8 min (T₀), 6.5 min (T_lag), 7.8 min (T_release), and 30 min, respectively, after initiation of wet-heat treatment. The baselines of the Raman spectra were shifted for display. The arrows with the dotted vertical lines below them mark the positions of Raman bands at 783 and 1,655 cm⁻¹, and the dotted line at 1,668 cm⁻¹ marks the Raman band characteristic of denatured protein. The scale bars in the images are 3 μm, and all images are at the same scales. Circles on the images are the fitting of the edges of DIC images and fluorescence images, as described in Materials and Methods. (B) Raman scattering intensities of the spore analyzed in panel A. The Raman scattering intensities at CaDPA-, protein-, and nucleic acid-specific bands, in arbitrary units (a.u.), were determined at various times and plotted as a function of incubation time at 80°C. Plots a to c are for the bands at 1,017, 1,655, and 783 cm⁻¹, respectively. In plot a the upward and downward arrows mark the positions of T_lag and T_release, respectively. In plot b the upward arrow marks the position of T_d.