Laser Raman Spectroscopy of Lyophilized Bacterial Spores

Abstract

Laser-excited Raman spectra were examined in lyophilized spores of Bacillus cereus. In a comparison of the spectrum of the dormant spore with that of the germinated spore, we found several Raman bands which occurred in the former but not in the latter. Among these Raman bands, the 1,573, 1,395, 1,017, 822, and 662 cm-1 bands were assigned to the vibrational frequencies of calcium dipicolinate (CaDPA). No Raman bands and peaks due to dipicolinic acid (H2DPA) were observed. This Raman evidence indicates that CaDPA is the predominant DPA species in this spore. We also proposed a tentative assignment for other vibrational frequencies due to several components of the spore.