Berberine levels accumulated by germinated spores as determined by LTRS.

(A, B) Average Raman spectra of 50 individual spores germinated with various berberine concentrations for 60 min at 37°C in LB medium plus 10 mM L-valine without (A) or with (B) 20 μg/mL INF55. (C) The percentage of germinated spores that contain berberine. (D) The average berberine level in germinated spores that contained berberine. Berberine levels were determined by the Raman band intensities at 1,518 cm-1 in spores, calibrated by Raman band intensities of berberine solutions of known concentration. (E, F) Raman spectra of 10 individual spores germinated as described above with 35 μg/mL berberine without (E) or with (F) 20 μg/mL INF55.