Figure 4.

Quantitative analysis of the important spectral features that contribute to the RF classification of the six prokaryotic species

(A) Comparison of the Raman intensities at ∼1152 cm⁻¹ (white boxes) and ∼1518 cm⁻¹ (gray boxes) between T. thermophilus and N. viennensis. The intensity plotted here was evaluated from each single-cell spectrum (smoothed using 15-point Savitzky–Golay polynomial filter of degree 2) by subtracting the minimum value in 1134.2–1173.8 cm⁻¹ from the maximum value in 1145.7–1154.0 cm⁻¹ or by subtracting the minimum value in 1497.8.7–1537.1 cm⁻¹ from the maximum value in 1516.7–1519.8 cm⁻¹.

(B) Comparison of the CH-stretching Raman intensities at ∼2850 cm⁻¹ among the six prokaryotic species studied. The intensity plotted here was evaluated from each single-cell spectrum (smoothed using 15-point Savitzky–Golay polynomial filter of degree 2) by summing up the intensities in 2830.5–2849.3 cm⁻¹ (the region indicated by the dashed rectangular box in Figure 2A). Different letters indicate statistically significant differences (P < 0.05) among the six species by a nonparametric Kruskal–Wallis test followed by a post hoc Dunn–Holland–Wolfe multiple comparison tests.